Book:
Plastics Materials: John A. Brydson
Principles of Polymerization: George Odian
Properties of Polymers: D.W. Van Krevelen
Polymer Materials: Sukumar Maiti
Polymer Technology
(MS41004)
Prof. Dr. Susanta Banerjee
Institute Chair Professor
Materials Science Centre
IIT Kharagpur
1
Materials and civilisation
Stone age
(Before 5000 BC)
Copper age (5000 - 3000 BC)
Bronze age(3000 - 800 BC)
Iron age(800 BC - 40 AD)
Plastic age ?
2
Types of materials
Metal
Semiconductors
Ceramic
Composites
Molecular materials
3
Polymer
Biomaterials
History of polymers (1500 – present)
1500’s
British explorers discover
ancient Mayan civilization in
Central America. The Mayans
are assumed to be the among
The first to find an application
of polymers, as their children
Were fond of playing with balls
made from local rubber tree
1839
Charls Godyear discovers
Vulcanisation . Vulcanised
rubber is much is much more
durable than its natural part
1917
X-ray crrstallography is
invented as a method of
analyzing crystal structure.
M. Polanyi discover the chemical
structure of cellulose. This
establishes the fact that polymer unit
cells contain Sections of long chain
molecules rather than small molecules
1907
The oldest recorded
synthetic Plastic is fabricated
by Leo Bakeland. Bakelite’s
hardness and high heat resistance
made it an excellent choice as an
electrical insulator and many article
1920
Hermann Staudinger
pulished his classic paper “Uber
Polymerization”. Demonstrated the
existence of macromolecules
Nobel Prize in
Chemistry in1953
for his discoveries
in the field of
macromolecular
chemistry
1927
Large scale production of
PVC resins begins. Widely used
today to make plumbing pipe,
tiles and bottles.
1930
Polystyrene invented.
Material used in video cassettes ,
toys and other packaging.
1970
Development of liquid
crystalline polymer.Common
application in electronic
devices and Aircraft engines
Xydar® LCP is a glass fiber or mineral-filled
resin that features excellent flow properties.
It can be injection molded into thin-wall
components and has outstanding strength
at extreme temperatures to 300°C. Xydar®
resin isinherently FR, transparent to
microwave radiation, and resistant
to virtually all chemicals.
1971
Kevelar developed. High
strengthmaterial that can
withstand temp. upto 300 oC.
Used in bullet proof vests, fire proof
germents for fire fighting and
auto raching.
HBA/TPA/BP
1938
W. Carotheror (DuPont )
Invented Nylon, is a
common material in clothing
and different engineering
products
1941
Polyethylene developed.
Billions of poundes of LDPE
and HDPE is produced today,
everything for packaging
film, piping to toy
1976
The polymer product
industry outstrip steel as
the most widely used material
per unit volume. We now use
more plastic than steel,
aluminum and copper combined
5
World consumption of polymers
6
Use of polymers in different sector
(European Union)
7
Cost
Performance
8
Packaging
9
Sporting Goods
10
Consumer products
11
Aircraft
Airbus A380
12
Automotive
The 100% plastic car – no longer an imaginary concept !!!
13
Naval Ships
14
Polymers
•
The earliest synthetic polymer was developed in 1906, called Bakelite.
•
The development of modern plastics started in 1920s using raw
material extracted from coal and petroleum products (Ethylene).
Ethylene is called a monomer.
•
Polymers are long-chain molecules and are formed by polymerization
process, linking and cross linking a particular building block (monomer, a
unit cell).
•
The term polymer means many units repeated many times in a
chainlike structure.
•
Most monomers are organic materials, atoms are joined in covalent
bonds (electron-sharing) with other atoms such as oxygen, nitrogen,
hydrogen, sulfur, chlorine,….
15
Products from Bakelite
16
Polymer Building Blocks
 Hydrogen
 Carbon (key)
 Oxygen
 Nitrogen
 Fluorine
 Silicon
 Sulfur
 Chlorine
 Phosphorus
17
Monomer to Polymer
HOOC-R-COOH
HO-Ar-OH
CH3-CH3
CH2=CH2 *CH2-CH2*
18
Polymer, Monomer; Structure unit,
degree of polymerization
Poly- means "many" and -mer means "part" or "segment". Mono
means "one".
So, monomers are those itty bitty molecules that can join together
to make a long polymer chain.
Monomer : material employed in the preparation of the polymer. They
are functional & minimum functionality is two.
Many many many MONOmers make a POLYmer!
19
Structure units are connected to one another
in the polymer chain, or
polymeric structure, by covalent bonds.
Repeat unit: The atoms that make up the backbone of a polymer chain
come in a regular order, and this order repeats itself all along the length of the
polymer chain. For example, look at polypropylene :
CH2 CH CH2 CH CH2 CH CH2 CH
CH3
CH3
CH3
CH3
Its backbone chain is made up of just two carbon atoms repeated over and
over again. One carbon atom has two hydrogen atoms attached to it, and the
other carbon atom has one hydrogen atom and one pendant methyl group
(CH3). This is called the repeat structure or the repeat unit. To make things
simple, we usually only draw one unit of the repeat structure, like this:
CH2 CH
CH3 n
20
Another example: styrene monomers join together
to make polystyrene:
CH2
CH
CH2
CH
n
Styrene monomer
Polystyrene repeat unit
CH2 CH CH2 CH CH2 CH CH2 CH
21
Degree of polymerization: refers to the number average
obtained by dividing the total number of structural units by the total
number of molecules.
Polymer molecular weight:
M = DP x Mo
CH2 CH
Mo： molecular weight of repeating unit
DP： Av. Degree of polymerization
CH3 n
As for example look at polypropylene
If n = 1000, DP is 1000, This means that
CH2
propylene unit has repeated 1000 times
and Mo for the repeat unit is 42, the molecular
weight (M) of the polymer is 42 X 1000 = 42000 g/mol
CH
CH3
1000
22
Molecular Weight of Polymers
Unlike small molecules, polymers are typically a mixture of differently
sized molecules. Only an average molecular weight can be defined.
• Measuring molecular weight
• Size exclusion chromatography
• Viscosity
• Measurements of average molecular
weight (M.W.)
• Number average M.W. (Mn): Total
weight of all chains divided by no of
chains
• Weight average M.W. (Mw): Weighted
average. Always larger than Mn
• Viscosity average M.W. (Mv):
Average determined by viscosity
measurements. Closer to Mw than Mn
Molecular Weight Distribution
PDI = Mw/Mn
23
Molecular Weight of Polymers
a) Number average moleculare weight (Mn)
Mn: This gives you the true average weight
Let's say you had the following polymer sample:
2 chains: 1,000,000 Dalton
2,000,000
5 chains: 700,000 Dalton
3,500,000
10 chains: 400,000 Dalton
4,000,000
4 chains: 100,000 Dalton
400,000
2 chains: 50,000 Dalton
100,000
10,000,000
10,000,000/23 = 435,000 Dalton
1 Dalton = 1 g/mole
Mn = ∑niMi/∑ni
24
b) Weight Average Molecular Weight (Mw)
Mw: Since most of the polymer mass is in the heavier fractions, this gives
the average molecular weight of the most abundant polymer fraction by
mass.
2,000,000
 0.20  1,000,000  200,000
10,000,000
3,500,000
 0.35  700,000  245,000
10,000,000
4,000,000
 0.40  400,000  160,000
10,000,000
400,000
 0.04  100,000  4,000
10,000,000
100,000
 0.01 50,000  500
10,000,000
Total  609,500
Mw = ∑niMi2/∑niMi

25
Chemical Structure
CH2
Homoplymer- only one monomer
(repeating unit)
CH
n
-A – A – A – A – A – A – A –
CF2 CF2
CH2 CH
CH2 CH2
n
CH3 n
n
Copolymer – more than one monomer
CH2 CH2 CH2 CH
CH2
CH
CH2 CH CH CH2
n
CH3 n
26
Copolymers
 Alternating and random
-A–B–A–B–A–B–A–BCH2 CH2 CH2 CH CH2 CH2
CH3
CH2 CH CH2 CH2 CH2 CH
CH3 n
CH3
Block
-A-A-A-A-A-B-B-B-B-B-A-A-A-A-ACH2
CH
CH2 CH CH CH2
x
CH2 CH
y
z
n
-A-A-A-A-A-A-A-B-B-B-B-B-B-B-
Copolymers can be used to tailor functionality or
generate new phases and behaviors.
27
Copolymers
Graft
Polymer Science: Vasant Gowariker, N. V.
Viswanathan, Jayadev Sreedhar
Poly(styrene)-graft-poly(butadiene)
B-B-B-B-B-B-B
B
-A-A-A-A-A-A-A-A-A-A-A-A-A-A-AB
B-B-B-B-B-B
28
Various polymer architectures
29
• Homopolymers may not always satisfy all the requirements for various
practical applications.
• Thus, initially the trend was to develop new polymers from a wide variety of
monomers.
• For tailoring or modifying the properties of polymers, copolymerization has
been used as an effective technique.
• However, due to the economic and technical uncertainties associated with
synthesizing new polymers, recently efforts were focused on multiphase
polymeric systems to obtain materials with improved physical and chemical
properties and such considerations were the basis of polymer blends.
• Mixing two or more polymers together to produce blends is economically a
more attractive way than the copolymerization from the standpoint of
commercial applications.
• BLENDS: 1. Miscible; 2. Partially miscible; 3. Immiscible (Polymer A & B)
Viton
CH2=CH2
CF2=CF2
CF2=CF(CF3)
30
A
-(A)x-(B)y-
1/Tg(blend) = WA/TgA + WB/TgB
B
WA= 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100
WB= 100, 90, 80, 70, 60, 50, 40, 30. 20, 10, 0
2 Homopolymers, 9 copolymers
A
B
A = PPO, TgA = 210 oC
B = PS, TgB = 100 oC
Calculate cohesive energy density by
group contribution methods (Bondi)
Polymer blends of AB
By measuring the Tg of the blends (DSC)
31
Books
1. Plastics Materials, J. A. Brydson
2. Properties of Polymers, D. W. Van Krevelen
3. Principles of Polymerization, George Odian
32
What makes polymers different
1. Can bend and twist and get all tangled up
• Chain entanglement: Long polymer chains get entangled with each other. The
longer a polymer chain is, the more tangled up it can get.
• Since the chains are harder to pull out or separate, that can make things made out
of polymers stronger.
• When the polymer is melted (heated), the chains can flow past each other.
• Below the melting point, the chains can move, but only slowly. Thus the plastic is
flexible, but cannot be easily stretched.
• Below the glass transition point, the chains become locked and the polymer is rigid
33
2. Polymer Chains Stick to Other Polymer Chains
(Summation of Intermolecular Forces):
• Think of molecules as being like magnets. Some are like very weak
magnets, and some are like strong magnets. So, some can be pulled apart
easily, but others take a lot more energy to pull them apart.
• Polymer chains are like this too, but remember that they're much much
longer than molecules. When the chains stick together very strongly, it can be
really tough to pull them apart.
• If the chains happen to be straight and stiff and all lined up next to each
other, it can be REALLY hard to pull them apart. A great example is
cellulose in wood. The chains lay next to each other, straight and sticky (like
strong magnets). That makes trees (and lots of houses!) strong and tall.
34
3. Polymer Chains Move Slower than Molecules
(Time Scale of Motion)
• We can see what happening when polymers dissolve in a liquid. Those
long chains move around so slowly that they make the solution flow much
slower. The longer the chains, the slower the flow.
• If we measure how long it takes for a polymer solution to flow through a
special tube, we can learn more about how big the polymer chains are.
• By the way, the longer it takes to flow, the more viscous (viss-cuss) it is,
polymer enhances the viscosity of the medium
35
Natural
Classification of polymers
Semi synthetic
1. Source
Synthetic
2. Structure
3. Mol. force
(a) Linear polymer
(b) Branched chain polymer
(c) Cross–linked polymer
5. Method of polymerization
(a) Solution polymerization
(b) Melt or bulk polymerization
(c) Emulsion polymerization
(d) Suspension polymerization
(e) Interfacial polymerization
(a) Thermoplastic
(b) Thermosetting
(c) Elastomers
(d) Fibres
Continuous /
Batch
4. Mode of synthesis/
Mechanism of Polymerization
(a) Addition polymers/Chain
growth polymers
(b) Condensation polymers/
Step growth polymers
(c) Ring opening polymerizaion
(a) Crystalline
(b) Semi-crystalline
(c) Amorphous
36
1) Based on the source
a) Natural polymers: The polymers obtained from nature (plants and animals)
are called Natural polymers. Ex. Starch, cellulose, Natural rubbers, proteins,
Nucleic acid (DNA, RNA), cotton, silk, wool
H2C
H2C
H
C C
C C
H3C
CH2
H3C
CH2
H
n
n
trans-1,4-polyisoprene
(Plastic, at RT)
ciss-1,4-polyisoprene
(rubber, at RT)
Cellulose
(Fiber)
a) Synthetic polymers: The polymers which are prepared in the laboratories are
called synthetic polymers e.g. Poleythylene, polyvinylchloride (pvc), Nylon,
Teflon, Backelite, Terylene etc
CH2 CH2
n
CF2 CF2
CH2 CH
n
Cl
n
37
2) Based on the structure
a) Linear polymer : In linear polymer the monomeric units are linked together
to form linear chain. E.g. Polyethylene (HDPE), Nylon, polyester etc.
(b) Branched chain polymer : In branched chain polymers the monomeric units
are joined to form long chains with side chains (or) Branches of different
length. E.g. Glycogen, starch, L.D.P.E. etc
38
(c) Cross–linked polymer: In cross linked polymers the monomer units
are cross linked together to form a three dimensional Network. E.g.
Bakelite, melamine–formaldehyde Resin polystyrene–Butadiene.
39
3) Based on the molecular forces
a) Thermoplastic : Thermoplastics are the polymers which soften on heating and
harden on cooling reversibly. E.g. Polyethylene, polysterene, pvc, Teflon,
Nylon, sealing wax.
Linear or branched polymers which can be softened or melted when heat is
applied. Can be molded into any shape with processing techniques such as
injection molding or extrusion.
CH3
CH2 CH2
CH2 CH
n
CH3 n
O
C
CH3
O
O C
n
40
b) Thermosetting: Thermosetting plastics are the polymers which undergo
permanent change on heating(irreversible) E.g. Bakelite, Polyester,
Polysiloxanes.
• Normally are rigid materials.
• Network polymers in which chain motion is greatly restricted by a high
degree of crosslinking.
• Cannot be reshaped once formed
Crosslinked (Networked) – chains are connected to other chains
41
c) Elastomers: Elastomers are the polymers which posses elastic character.
E.g. Natural rubber
 Crosslinked (networked) rubbery polymers that can be stretched easily (3-10x
original size)
 Rapidly recover original dimensions when applied stress is released.
 Low degree of crosslinking
H2C
CH2
C C
H3C
H
n
Amorphous Polymer – Lightly Crosslinked
42
d) Fibres: Fibres are polymers in which the chains are held by
intermolecular forces like H–bond, Dipole–dipole interaction. E.g. Nylon,
poly Acrylonitrile H2N (CH2)6 NH2 + HOOC (CH ) COOH
2 4
O
HN
(CH2)6
NH C C(CH2)4
CH2
O
C
CH
C N
n
n
43
4) Based on the mode of synthesis (mechanism of
formation)
a) Addition polymers : A polymer formed by direct addition of repeated
monomer without the elimination of by product molecules are called Addition
polymer. E.g. Polyethylene, polypropylene, pvc, Teflon, orlun, Neoprene, pvp
(polyvinyl pyrolidone)
n CH2 CH2
CH2 CH2
n
b) Condensation polymers: A polymer formed by the condensation of two (or)
more monomers with the elimination of simple molecule like H2O, NH3, HCl,
alcohol etc. are called condensation polymer.E.g. Polyester, Nylon 6,6,
Bakelite, Polycarbonate
CH3
HO
C
O
OH +
Cl
C Cl
CH3
O
CH3
C
O
+ HCl
O C
CH3
n
O
O
O C
44
Semicrystalline Thermoplastic
45
Crystalline
Example: Polyethylene
46
47
Polymer Microstructure
CH2
CH2
Polyolefins with side chains have stereocenters on every other carbon
CH3
n
CH2
CH3 CH3 CH3 CH3 CH3 CH3 CH3
With so many stereocenters, the stereochemistry can be complex. There
are three main stereochemical classifications for polymers.
CH
CH3
Atactic: random orientation
Isotactic: All stereocenters have same orientation
Syndiotactic: Alternating stereochemistry
48
49
Polystyrene (PS)
Why is this important?
 Tacticity affects the physical properties
 Atactic polymers will generally be amorphous and could be soft,
flexible materials (Example: PP)
 Isotactic and syndiotactic polymers will be more crystalline, thus
harder and less flexible
 Polypropylene (PP) is a good example
 Atactic PP is a low Tg, gooey material
 Isoatactic PP is high melting (176º), crystalline, tough material that
is industrially useful
 Syndiotactic PP has similar properties, but is very clear. It is
harder to synthesize
51
Why Design with Polymers?
• Light weight, high strength to
weight ratio, particularly when
reinforced
Density
• Relatively low cost compared
to metals and composites
Cost
52
Why Design with Polymers?
 Corrosion resistance
 Low electrical and thermal conductivity, insulator
 Easily formed into complex shapes, can be formed,
casted and joined.
 Wide choice of appearance, colors and transparencies
Performance
Cost
Adaptability (soft, hard, crosslink etc)
53
Disadvantages of using Polymers
 Low strength
o
 Low useful temperature range (up to 600 F; 315 oC)
 Less dimensional stability over period of time (creep
effect)
 Aging effect, hardens and become brittle over time
 Sensitive to environment, moisture and chemicals
 Poor machinability
54
55
10
CH2
CH2
25
CH2
CH2
1200
500
15
CH2
CH2
1000
15
CH2
CH2
15
CH2
CH2
1800
30
CH2
CH2
2000
800
20
CH2
CH2
900
Total number of chains = 150
20
CH2
CH2
2200
Av. DP = 10*500+15*1000……./150
=211000/150 = 1406.6
56
Mechanical Properties of Various Plastics
Steel: 350 to 1900 MPa Brass: 200 to 850 MPa Aluminum: 100 to 550 MPa
57
Hardener
58
59
Polymer Synthesis
 There are two major classes of polymer formation
mechanisms
 Addition polymerization: The polymer grows by
sequential addition of monomers to a reactive site
 Chain growth is linear
 Maximum molecular weight is obtained early in the
reaction
 Step-Growth polymerization: Monomers react together
to make small oligomers. Small oligomers make
bigger ones, and big oligomers react to give polymers.
 Chain growth is exponential
 Maximum molecular weight is obtained late in the
reaction
60
Polyaddition
 Reactions in which monomers combine without
the elimination of a small molecule.
CH2
CH
X
CH2
CH
n
X
X = H, CH3, Cl, CN, Ph, COOCH3, COOH
 Usually
involves the breaking of a double
bond.
61
Polyaddition with Radicals
 Initiation – Creation of an active site (free
radical).
CH2
In
R
CH
RCH2 CH
X
X
 Propagation – Growth of polymer chain by
addition of a monomer to an active site and the
creation of a new active site.
n CH2
CH
X
RCH2 CH
X
RCH2 CH CH2 CH CH2 CH
X
X
n
X
62
O
C
O
-CO2
CH2
CH2
CH2R
CH2
R(CH2-CH2)n1-CH2=CH2
+
CH3-(CH2-CH2)n2-CH2-CH2R
63
Polyaddition with Radicals
 Termination – Growth of chain stops.

Combination – Two growing chains collide.

Disproportionation – A hydrogen atom is added to the
end of a growing chain.
64
Addition Polymerization
nA
A
In*
In
A A A A*
Initiation
In
Propagation
A A A A A*
n
*A
A
*A
A A A A
m
A A A A
m
In
In
A A A A A
A A A A A
In
n
n
A*
A A A A A
Combination
B A A A A
m
Chain Transfer
New reactive site
is produced
Disproportionation
Termination
Reactive site is consumed
MW
MW 
0
100
% conversion
A A A A A
n
k propagation
k ter mination
m
Types of Addition Polymerizations
Anionic
Ph
C3H7
Li
n
Li+
C4H9
Ph
Li+
C4H9
n
Ph
Ph
Ph
Radical
PhCO2•
Ph
n
Ph
PhCO2
n
Ph
Cationic
Ph
Cl3Al OH2
PhCO2
Ph
Ph
n
Ph
H
Ph
HOAlCl3
HOAlCl3
H
n
Ph
Ph
66
Common Polyolefins
Monomer
Ethylene
Polymer
Polyethylene
CH3
H3C
n
Repeat unit
CH3
CH3
n
Polypropylene
Propylene
CH3 CH3 CH3 CH3 CH3 CH3 CH3
CH3
Ph
n
Polystyrene
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Styrene
CH3
Cl
n
Poly(vinyl chloride)
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Vinyl Chloride
F2C CF2
Tetrafluoroethylene
F3C
Poly(tetrafluoroethylene): Teflon
F2
C
C
F2
F2
C
C
F2
F2
C
C
F2
F2
C
C
nF
2
F2
C
C
F2
F2
C
C
F2
CF3
67
Polycondensation
 Reactions in which small molecules (H2O, HCl)
are eliminated when the monomers combine.
O
n
O
O
O
O
O
+ n HN
2
O
NH2
O
O
O
HN
OH
HO
NH
O
O
Polyamide acid
O
H2O
N
O
n
O
N
O
n
O
+ (2n-1) H2O
68
O
H2N
O
NH2
O
O
N
N
O
O
O
O
O
O
O
O
O
O
NH2
N
O
O
N
O
69
Principles of polymerization
Textbook by George G. Odian
O
O
n HO C
C OH
O
O C
+
n HO CH2
CH2
OH
O
C O CH2 CH2
+ (2n-1) H 0
O
n
2
MF: C10H8O5 = 208 g/mol
70
Step-Growth Polymerization
Stage 1
n
n
Consumption
of monomer
Stage 2
Combination
of small fragments
Stage 3
Reaction of
oligomers to give
high molecular
weight polymer
71
Step-Growth Polymerization
•
Because high polymer does not form until the end of the reaction, high
molecular weight polymer is not obtained unless high conversion of monomer
is achieved.
DP = (1+r)/(1+r-2rp)
Where r = NA/NB
If there is no stoichiometric
Imbalance; NA = NB
DP = 1/(1-p)
p=1
DP = (1+r)/(1-r)
Degree of Polymerization
1000
100
DP = 1/(1-p)
10
1
0
DP = Degree of polymerization
p = mole fraction monomer
conversion
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Mole Fraction Conversion (p)
72
A polyimide is prepared by polycondensation of a diamine
with a dianhydride whose repeat unit structure is shown below:
O
C
O
C
N
N
C
O
O
C
O
n
Calculate the theoretical molecular weight of the polymer when
183 Kg of diamine (mol wt. 200 g/mol) and 200 Kg of
dianhydride (mol wt. 218 g/mol)
was used in the reaction, where the extent of reaction is 99%.
Calculate the amount of water (in Kg) will produce in this reaction.
73
Nylon-6,6
O
O
O
NaOH
Cl
4
Cl
Adipoyl chloride
H2N
4
NH2
Cl
O
N
H
4
1,6-Diaminohexane
O
Adipoyl chloride
in hexane
HO
N
H
4
O
N
H
4
4
Nylon 6,6
Diamine, NaOH, in H2O
H
6 carbon
diacid
N
H
H
n
6 carbon
diamine
Nylon-6,6
74
Nylon-6,6
Since the reactants are in different
phases, they can only react at the phase
boundary. Once a layer of polymer forms,
no more reaction occurs. Removing the
polymer allows more reaction to occur.
Adipoyl chloride
in hexane
Nylon 6,6
Diamine, NaOH, in H2O
75
Polyesters, Amides, and Urethanes
Monomer
Polymer
O
HO2C
CO2H
Terephthalic
acid
OH
HO
Ethylene
glycol
NCO
4,4-diisocyantophenylmethane
O
HO
H
N
H2 H2
O C C O H
Poly(ethylene terephthalate
n
Ester
A2 or B2
H2
C
OCN
HO
O
H2
C
OH
HO
Spandex
Ethylene
glycol
O
H2 H2
H
N
O C C O H
AB
HO-R-COOH
Urethane linkage
n
76
A2 + B2
PET
A2 = Terephthalic acid
B’2 = Ethylene glycol, HO-CH2-CH2-OH
Moles of A2 = Moles of B’2
A2 + B’2 +B’’2
-(PET)-(PBT)-
A2 = Terephthalic acid
B’2 = Ethylene glycol
B’’2= Butylene glycol
Moles of A2 = Moles of B’2 +Moles moles of B’’2
HO-CH2-CH2-OH
HO-CH2-CH2-CH2-CH2-OH
77
AB
Δ
Vacuum
DL-Lactic acid
DLPLA-2/ DLPLA-2
Δ
Vacuum
DL-Lactic acid
Glycolic acid
PLGA-7515/ PLGA-7520
78
Physical Properties
Linear Polymer
Stretch
The chains can be stretched, which causes
them to flow past each other. When released,
the polymer will not return to its original form.
Cross-Linked Polymer
Stretch
Relax
The cross-links hold the chains together.
When released, the polymer will return to it's
original form.
79
Mechanical Properties
• Stress and strain: What are they and why are
they used instead of load and deformation?
• Elastic behavior: When loads are small, how much
deformation occurs? What materials deform least?
• Plastic behavior: At what point does permanent
deformation occur? What materials are most
resistant to permanent deformation?
• Toughness and ductility: What are they and how
do we measure them?
80
Elastic Deformation
1. Initial
2. Small load
3. Unload
bonds
stretch
return to
initial
d
F
F
Linearelastic
Elastic means reversible!
d
81
Non-Linearelastic
Plastic Deformation (Metals)
1. Initial
2. Small load
bonds
stretch
& planes
shear
delastic + plastic
3. Unload
planes
still
sheared
dplastic
F
F
Plastic means permanent!
linear
elastic
linear
elastic
dplastic
82
d
Engineering Stress
• Tensile stress, s:
• Shear stress, t:
Ft
Area, Ao
Area, Ao
Ft
Ft
lb f
N
= 2 or
s=
2
in
m
Ao
original area
before loading
83
Ft
F
Fs
Fs
Fs
t=
Ao
F
 Stress has units:
N/m2 or lbf /in2
Ft
Common States of Stress
• Simple tension: cable
F
F
A o = cross sectional
area (when unloaded)
F
s
s
Ao
s
• Torsion (a form of shear): drive shaft
M
Ac
M
84
Fs
Ski lift
(photo courtesy
P.M. Anderson)
Ao
Fs
t 
Ao
2R
Note: t = M/AcR here.
OTHER COMMON STRESS STATES (i)
• Simple compression:
Ao
Canyon Bridge, Los Alamos, NM
(photo courtesy P.M. Anderson)
Balanced Rock, Arches
National Park
(photo courtesy P.M. Anderson)
85
F
s
Ao
Note: compressive
structure member
(s < 0 here).
OTHER COMMON STRESS STATES (ii)
• Bi-axial tension:
Pressurized tank
(photo courtesy
P.M. Anderson)
Fish under water
sq > 0
sz > 0
86
• Hydrostatic compression:
sh< 0
(photo courtesy
P.M. Anderson)
Engineering Strain
• Tensile strain:
• Lateral strain:
d/2
e  d
Lo
wo
• Shear strain:
-dL
eL 
wo
Lo
dL /2
q
g = x/y = tan q
x
90º - q
y
90º
87
Strain is always
dimensionless.
Adapted from Fig. 7.1 (a) and (c), Callister & Rethwisch 3e.
Stress-Strain Testing
• Typical tensile test
machine
extensometer
• Typical tensile
specimen
specimen
Adapted from
Fig. 7.2,
Callister &
Rethwisch 3e.
gauge
length
Adapted from Fig. 7.3, Callister & Rethwisch 3e. (Fig. 7.3 is taken from H.W.
Hayden, W.G. Moffatt, and J. Wulff, The Structure and Properties of Materials,
Vol. III, Mechanical Behavior, p. 2, John Wiley and Sons, New York, 1965.)
88
Linear Elastic Properties
• Modulus of Elasticity, E:
(also known as Young's modulus)
• Hooke's Law:
s=Ee
s
F
E
e
Linearelastic
89
F
simple
tension
test
Poisson's ratio, n
• Poisson's ratio, n:
eL
eL
ne
metals: n ~ 0.33
ceramics: n ~ 0.25
polymers: n ~ 0.40
Units:
E: [GPa] or [psi]
n: dimensionless
90
e
-n
n > 0.50 density increases
n < 0.50 density decreases
(voids form)
Mechanical Properties
 Slope of stress strain plot (which is
proportional to the elastic modulus) depends
on bond strength of metal
Adapted from Fig. 7.7,
Callister & Rethwisch 3e.
91
Other Elastic Properties
• Elastic Shear
modulus, G:
t
M
G
t=Gg
• Elastic Bulk
modulus, K:
V
P = -K
Vo
g
M
P
P
K
V P
Vo
• Special relations for isotropic materials:
E
G
2(1 + n)
92
simple
torsion
test
E
K
3(1 - 2n)
P
pressure
test: Init.
vol =Vo.
Vol chg.
= V
Young’s Moduli: Comparison
Metals
Alloys
1200
1000
800
600
400
E(GPa)
200
100
80
60
40
Graphite
Composites
Ceramics Polymers
/fibers
Semicond
Diamond
Tungsten
Molybdenum
Steel, Ni
Tantalum
Platinum
Cu alloys
Zinc, Ti
Silver, Gold
Aluminum
Magnesium,
Tin
Si carbide
Al oxide
Si nitride
Carbon fibers only
CFRE(|| fibers)*
<111>
Si crystal
Aramid fibers only
<100>
AFRE(|| fibers)*
Glass -soda
Glass fibers only
GFRE(|| fibers)*
Concrete
109 Pa
10
8
6
4
2
1
0.8
0.6
0.4
93
GFRE*
20
0.2
CFRE*
GFRE( fibers)*
Graphite
Polyester
PET
PS
PC
CFRE( fibers) *
AFRE( fibers) *
Epoxy only
PP
HDPE
PTFE
LDPE
Wood(
grain)
Based on data in Table B.2,
Callister & Rethwisch 3e.
Composite data based on
reinforced epoxy with 60 vol%
of aligned
carbon (CFRE),
aramid (AFRE), or
glass (GFRE)
fibers.
Useful Linear Elastic Relationships
• Simple tension:
d  FL o d  -n Fw o
L
EA o
EA o
F
a
wo
2ML o

r o4 G
M = moment
a = angle of twist
d/2
Ao
dL /2
• Simple torsion:
Lo
Lo
2ro
• Material, geometric, and loading parameters all
contribute to deflection.
• Larger elastic moduli minimize elastic deflection.
94
Plastic (Permanent) Deformation
(at lower temperatures, i.e. T < Tmelt/3)
• Simple tension test:
Elastic+Plastic
at larger stress
engineering stress, s
Elastic
initially
permanent (plastic)
after load is removed
ep
engineering strain, e
plastic strain
95
Adapted from Fig. 7.10 (a),
Callister & Rethwisch 3e.
Yield Strength, sy
• Stress at which noticeable plastic deformation has
occurred.
when ep = 0.002
tensile stress, s
sy
sy = yield strength
Note: for 2 inch sample
e = 0.002 = z/z
 z = 0.004 in
engineering strain, e
ep = 0.002
96
Adapted from Fig. 7.10 (a),
Callister & Rethwisch 3e.
Yield Strength : Comparison
Metals/
Alloys
2000
Graphite/
Ceramics/
Semicond
Polymers
Composites/
fibers
97
200
Al (6061) ag
Steel (1020) hr
Ti (pure) a
Ta (pure)
Cu (71500) hr
100
70
60
50
40
Al (6061) a
30
20
10
Tin (pure)
¨
dry
PC
Nylon 6,6
PET
PVC humid
PP
HDPE
LDPE
Hard to measure,
300
in ceramic matrix and epoxy matrix composites, since
in tension, fracture usually occurs before yield.
700
600
500
400
Ti (5Al-2.5Sn) a
W (pure)
Cu (71500) cw
Mo (pure)
Steel (4140) a
Steel (1020) cd
since in tension, fracture usually occurs before yield.
1000
Hard to measure ,
Yield strength, sy (MPa)
Steel (4140) qt
Room temperature
values
Based on data in Table B.4,
Callister & Rethwisch 3e.
a = annealed
hr = hot rolled
ag = aged
cd = cold drawn
cw = cold worked
qt = quenched & tempered
Tensile Strength, TS
• Maximum stress on engineering stress-strain curve.
Adapted from Fig. 7.11,
Callister & Rethwisch 3e.
TS
F = fracture or
ultimate
strength
engineering
stress
sy
Typical response of a metal
Neck – acts
as stress
concentrator
strain
engineering strain
• Metals: occurs when noticeable necking starts.
• Polymers: occurs when polymer backbone chains are
aligned and about to break.
98
Tensile Strength: Comparison
Metals/
Alloys
Tensile strength, TS (MPa)
5000
3000
2000
1000
300
200
100
40
30
Polymers
20
Composites/
fibers
C fibers
Aramid fib
E-glass fib
Steel (4140) qt
W (pure)
Ti (5Al-2.5Sn)aa
Steel (4140)cw
Cu (71500)
Cu (71500) hr
Steel (1020)
Al (6061) ag
Ti (pure) a
Ta (pure)
Al (6061) a
AFRE(|| fiber)
GFRE(|| fiber)
CFRE(|| fiber)
Diamond
Si nitride
Al oxide
Si crystal
<100>
Glass-soda
Concrete
Nylon 6,6
PC PET
PVC
PP
HDPE
Graphite
wood(|| fiber)
GFRE( fiber)
CFRE( fiber)
AFRE( fiber)
LDPE
10
wood (
1
99
Graphite/
Ceramics/
Semicond
fiber)
Room temperature
values
Based on data in Table B4,
Callister & Rethwisch 3e.
a = annealed
hr = hot rolled
ag = aged
cd = cold drawn
cw = cold worked
qt = quenched & tempered
AFRE, GFRE, & CFRE =
aramid, glass, & carbon
fiber-reinforced epoxy
composites, with 60 vol%
fibers.
Ductility
• Plastic tensile strain at failure:
Lf - Lo
x 100
%EL 
Lo
smaller %EL
Engineering
tensile
stress, s
larger %EL
Lo
Ao
Af
Adapted from Fig. 7.13,
Callister & Rethwisch 3e.
Engineering tensile strain, e
• Another ductility measure:
100
%RA =
Ao - Af
x 100
Ao
Lf
Toughness
• Energy to break a unit volume of material
• Approximate by the area under the stress-strain curve.
Engineering
tensile
stress, s
small toughness (ceramics)
large toughness (metals)
very small toughness
(unreinforced polymers)
Adapted from Fig. 7.13,
Callister & Rethwisch 3e.
Engineering tensile strain, e
Brittle fracture: elastic energy
Ductile fracture: elastic + plastic energy
101
Resilience, Ur
 Ability of a material to store energy
 Energy stored best in elastic region
Ur  
ey
0
sde
If we assume a linear
stress-strain curve this
simplifies to
1
Ur @ sy e y
2
Adapted from Fig. 7.15,
Callister & Rethwisch 3e.
102
Elastic Strain Recovery
sy i
D
syo
Stress
2. Unload
1. Load
3. Reapply
load
Strain
Adapted from Fig. 7.17,
Callister & Rethwisch 3e.
103
Elastic strain
recovery
Mechanical Properties
Ceramic materials are more brittle than metals.
Why is this so?
 Consider mechanism of deformation


In crystalline, by dislocation motion
In highly ionic solids, dislocation motion is difficult
 few slip systems
 resistance to motion of ions of like charge (e.g., anions)
past one another
104
Flexural Tests – Measurement of Elastic Modulus
• Room T behavior is usually elastic, with brittle failure.
• 3-Point Bend Testing often used.
-- tensile tests are difficult for brittle materials.
F
cross section
L/2
d
b
rect.
L/2
Adapted from Fig. 7.18,
Callister & Rethwisch 3e.
R
d = midpoint
circ.
deflection
• Determine elastic modulus according to:
F
x
slope =
F
d
d
linear-elastic behavior
105
F L3
E
d 4bd 3
(rect. cross section)
F L3
(circ. cross section)
E
4
d 12R
Flexural Tests – Measurement of Flexural Strength
• 3-point bend test to measure room-T flexural strength.
cross section
d
b
rect.
L/2
F
L/2
Adapted from Fig. 7.18,
Callister & Rethwisch 3e.
R
d = midpoint
circ.
deflection
location of max tension
• Flexural strength:
sfs 
sfs 
106
3Ff L
2bd
2
Ff L
R
3
• Typical values:
sfs (MPa) E(GPa)
Si nitride
250-1000 304
Si carbide
100-820 345
Al oxide
275-700 393
glass (soda-lime) 69
69
Material
(rect. cross section)
(circ. cross section)
Data from Table 7.2, Callister & Rethwisch 3e.
Mechanical Properties of Polymers –
Stress-Strain
Behavior
brittle
polymer
plastic
elastomer
elastic moduli
– less than for metals
Adapted from Fig. 7.22,
Callister & Rethwisch 3e.
• Fracture strengths of polymers ~ 10% of those for metals
• Deformation strains for polymers > 1000%
107
– for most metals, deformation strains < 10%
107
Influence of T and Strain Rate on Thermoplastics
• Decreasing T...
-- increases E
-- increases TS
-- decreases %EL
• Increasing
strain rate...
-- same effects
as decreasing T.
s(MPa)
80 4°C
60
20°C
40
Plots for
semicrystalline
PMMA (Plexiglas)
40°C
20
0
60°C
0
0.1
0.2
e
to 1.3
0.3
Adapted from Fig. 7.24, Callister & Rethwisch 3e. (Fig. 7.24 is from T.S.
Carswell and J.K. Nason, 'Effect of Environmental Conditions on the
Mechanical Properties of Organic Plastics", Symposium on Plastics,
American Society for Testing and Materials, Philadelphia, PA, 1944.)
108
108
Time-Dependent Deformation
• Stress relaxation test:
-- strain in tension to eo
and hold.
-- observe decrease in
stress with time.
tensile test
eo
s(t)
time
• Relaxation modulus:
109
for T > Tg.
5
10
Er (10 s) 3
in MPa 10
rigid solid
(small relax)
transition
region
1
10
10-1
strain
s(t )
E r (t ) 
eo
• There is a large decrease in Er
viscous liquid
10-3 (large relax)
(amorphous
polystyrene)
Adapted from Fig.
7.28, Callister &
Rethwisch 3e. (Fig.
7.28 is from A.V.
Tobolsky, Properties
and Structures of
Polymers, John
Wiley and Sons, Inc.,
1960.)
60 100 140 180 T(°C)
Tg
• Representative Tg values (C):
PE (low density)
PE (high density)
PVC
PS
PC
- 110
- 90
+ 87
+100
+150
Selected values from
Table 11.3, Callister
& Rethwisch 3e.
109
Hardness
• Resistance to permanently indenting the surface.
• Large hardness means:
-- resistance to plastic deformation or cracking in
compression.
-- better wear properties.
apply known force
measure size
of indent after
removing load
e.g.,
10 mm sphere
D
most
plastics
brasses
Al alloys
Smaller indents
mean larger
hardness.
d
easy to machine
steels
file hard
cutting
tools
increasing hardness
110
nitrided
steels
diamond
Hardness: Measurement
Rockwell
No major sample damage
 Each scale runs to 130 but only useful in range 20100.
 Minor load
10 kg
 Major load
60 (A), 100 (B) & 150 (C) kg


A = diamond, B = 1/16 in. ball, C = diamond
HB = Brinell Hardness
TS (psia) = 500 x HB
 TS (MPa) = 3.45 x HB

111
Hardness: Measurement
112
True Stress & Strain
Note: S.A. changes when sample stretched
 True stress
sT  s1 + e 
sT  F Ai
 True strain
eT  ln i  o 
eT  ln1 + e 
Adapted from Fig. 7.16,
Callister & Rethwisch 3e.
113
Hardening
s
• An increase in sy due to plastic deformation.
large hardening
sy
1
sy
small hardening
0
e
• Curve fit to the stress-strain response:
 
sT  K eT
“true” stress (F/A)
114
n
hardening exponent:
n = 0.15 (some steels)
to n = 0.5 (some coppers)
“true” strain: ln(L/Lo)
Variability in Material Properties
 Elastic modulus is material property
 Critical properties depend largely on sample flaws
(defects, etc.). Large sample to sample variability.
 Statistics
n

Mean
 xn
x
n
1
2 2

Standard Deviation
n
x i - x  

s
 n -1 


where n is the number of data points
115
Design or Safety Factors
• Design uncertainties mean we do not push the limit.
• Factor of safety, N
Often N is
sworking 
sy
between
1.2 and 4
N
• Example: Calculate a diameter, d, to ensure that yield does
not occur in the 1045 carbon steel rod below. Use a
factor of safety of 5.
sworking 
220,000N


 d /4
2
5
sy
N
1045 plain
carbon steel:
sy = 310 MPa
TS = 565 MPa
d = 0.067 m = 6.7 cm
116
F = 220,000N
d
Lo
• Stress and strain: These are size-independent
measures of load and displacement, respectively.
• Elastic behavior: This reversible behavior often
shows a linear relation between stress and strain.
To minimize deformation, select a material with a
large elastic modulus (E or G).
• Plastic behavior: This permanent deformation
behavior occurs when the tensile (or compressive)
uniaxial stress reaches sy.
• Toughness: The energy needed to break a unit
volume of material.
• Ductility: The plastic strain at failure.
117
Tensile strength function of
Mol. Wt. of the polymer
Strength as a function of molecular weight. At low molecular weight, the strength is
too low for the polymer material to be useful. At high molecular weight, the strength
increases eventually saturating to the infinite molecular weight result of S∞
.
118
Mechanical Properties
 i.e. stress-strain behavior of polymers
brittle polymer
sFS of polymer ca. 10% that of metals
plastic
elastomer
elastic modulus
– less than metal
Strains – deformations > 1000% possible
(for metals, maximum strain ca. 10% or less)
119
Melting and Glass Transition Temperature
• Melting of a crystalline polymer
– transforming solid with an ordered structure to a viscous
liquid with a highly random structure
• Amorphous glass transitions
– transformation from a rigid material to one that has rubberlike
characteristics
– temperature has large effect on chain flexibility
• Below glass transition temperature, Tg, polymers are usually
brittle and glass-like in mechanical behavior.
• Above glass transition, Tg, polymers are usually more elastic.
Why is That?
Bond rotations are “freezing” which means chains can’t slip past
each other so polymer becomes brittle, (no plastic deformation)
120
Melting vs. Glass Transition Temp.
What factors affect Tm and Tg?



Both Tm and Tg increase with
increasing chain stiffness
Chain stiffness increased by
1.
Bulky side groups
2.
Polar groups or side groups
3.
Double bonds or aromatic
chain groups
Regularity – effects Tm only
121
121
DSC plot of semicrystalline polymers
122
Thermal Analysis
Differential Scanning
Calorimetry (DSC)
Measure heat absorbed
or liberated during
heating
or cooling
Thermal Gravimetric
Analysis (TGA)
Measure change in weight
during heating or cooling
Differential Scanning Calorimetry
(DSC)
Calorimeter-Heat flow in sample
Differential calorimeter-heat flow in sample vs
referance as function of time (mJ/sec).
•Differential Scanning Calorimetry (DSC)
measures the temperatures and heat flows
associated with transitions in materials as a
function of time and temperature in a
controlled atmosphere.
•These measurements provide quantitative
and qualitative information about physical
and chemical changes that involve
endothermic or exothermic processes, or
changes in heat capacity.
Conventional DSC
Empty
Sample
Metal
1
Sample
Temperature
Metal Metal
2
1
Metal
2
Reference
Temperature
Temperature
Difference =
Heat Flow
•A “linear” heating profile even for isothermal methods
Modes and principles of operation (1)
(b) Power compensated DSC: Temperature differences between the sample and
reference are ‘compensated’ for by varying the heat required to keep both pans at the
same temperature. The energy difference is plotted as a function of sample temperature
(c) Heat flux DSC ultilizes a single furnace. Heat flow into both sample and reference
material via an electrically heated constantan thermoelectric disk and is proportional to
the difference in output of the two themocouple junctions
a) DTA: difference in temperature between the sample and reference is plotted
against sample temperature
Diagram of a DSC apparatus
• A DSC apparatus is built
around
- a differential detector
- a signal amplifier
- a furnace
- a temperature controller
- a gas control device
- a data acquisition device
Gas
control
Sample
Furnace
Reference
Detectors
Microvolt
amplifier
Furnace
controller
Data
acquisitio
n
DSC measures:•Glass transitions
•Melting and boiling points
•Crystallisation time and temperature
•Percent crystallinity
•Heats of fusion and reactions
•Specific heat capacity
•Oxidative/thermal stability
•Rate and degree of cure
•Reaction kinetics
•Purity
Heat Flow -> exothermic
DSC Thermogram
Cross-Linking
(Cure)
Crystallisation
Glass
Transition
Melting
Temperature
6
Oxidation
Main Sources of Errors
•Calibration
•Contamination
•Sample preparation – how sample is loaded into a pan
•Residual solvents and moisture.
•Thermal lag
•Heating/Cooling rates
•Sample mass
•Processing errors
Sample preparation
Form of sample: bulk solid, powder (pressed), liquid.
Amount of sample: 3-5mg.
DSC Pan: Al, Pt, stainless steel, Ag, Cu, Al2O3
Sample Preparation : Shape
• Keep sample as thin as possible (to minimise thermal
gradients)
• Cover as much of the pan bottom as possible
• Samples should be cut rather than crushed to obtain a
thin sample (better and more uniform thermal contact
with pan)
99
Operation procedures
Calibration of instrument
•Temperature, heat of reaction, heat capacity
scale using high purity standards (In, Sn, Bi,
Pb,Au)
•Baseline correction for a given scan rate (1 40K/min).
•Weight samples before (and maybe after)
experiment.
Type of DSC experiments
1.
2.
Dynamic heating - thermodynamic properties
Isothermal heating - kinetic parameters
1. Dynamic heating:- Constant heat rate mode. (e.g. heat flow vs.
temperature).
What can we characterise?
Information:
1. Transformation temperature (e.g. onset, peak).
2. Transformation enthalpy (e.g. area under the peak).
3. Activation energy for transformation (e.g. Kissinger
analysis)
2.)Isothermal heating mode:Heating at a fixed temperature over a time interval.(e.g. heat flow vs. time)
THERMOGAVIMETRIC ANALYSIS (TGA)

Principle: TGA measures the amount and the rate of weight change
of a material with respect to temperature or time in controlled
environments.

.
A TGA consists of three major parts a furnace,
1. A microgram balance,
2. An auto sampler and
3. A thermocouple.
Instrument





Instrument used for thermogravimetry is “Thermobalance”.
Data recorded in form of curve known as ‘Thermogram’
The furnace can raise the
temperature as high as
1000°C or more which is made of quartz.
The auto sampler helps to
load the
samples on
to
the microbalance.
The thermocouple sits right above the sample.
Care should be taken at all times that the thermocouple is not
in touch with the sample which is in a platinum pan.
• A technique that permits the
continuous weighing of a
sample as a function of
temperature and/or as a
function of time at a desired
temperature
TGA Curve of Calcium Oxalate
142
143
TGA plot of (a) PS, (b) Pure PC,
(c) PC/Carbonyl Iron Composite
145
146
147
10 oC/min, air
148
149
Sample Preparation
Sample preparation has a significant effect in obtaining good data.
It is suggested that maximizing the surface area of the sample in a
TGA pan
improves resolution and reproducibility of weight
loss temperatures.
The sample weight affects the accuracy of weight loss
measurements.
Typically 10-20mg of sample is preferred in most applications.
Whereas, if the sample has volatiles 50-100mg of sample is
considered adequate.
It is to be noted that most TGA instruments have baseline drift of
±0.025mg which is ±0.25% of a 10mg sample.
Experimental Conditions


Heating Rate
Purge gas
Experimental Conditions -Heating Rate
Samples are heated at a rate of 10 or 20°C/min in most
cases.
 Lowering the heating rates is known to improve the
resolution of overlapping weight losses.

Experimental Conditions -Purge gas
• Nitrogen is the most common gas used to purge samples in TGA due
to its inert nature.
• Whereas, helium provides the best baseline.
• Air is known to improve resolution because of a difference in the
oxidative stability of components in the sample.
• Vacuum may be used where the sample contains volatile components,
which helps improve separation from the onset of decomposition
since the volatiles come off at lower temperatures in vacuum.
• e.g. oil in a rubber tire product.
Calibration
Blank test
 Calibration of mass changes
 Calibration of temperature

Applications of TGA





Determination of the bound and unbound water in the
suspension of Milk of Magnesia (MoM), used as a laxative.
In an overview of thermal analysis testing it is always
preferable to do a TGA experiment on unknown samples
before doing a DSC experiment (especially for
pharmaceuticals).
Decomposition of pharmaceuticals renders products which are
insoluble and generally sticky on the inside of a DSC cell.
These products will lower the life use of a DSC cell.
Therefore, know the decomposition temperatures of all drugs
and heat in a DSC evaluation to 50°C below those
temperatures.
Applications of TGA

Evaporation of free (unbound) water begins at room
temperature due to dry gas flowing over the sample.


Dehydration/Desolvation of bound water almost always
begins at temperatures above room temperature and
typically 125°C.

Decomposition can have multiple stages (weight losses)
but the presence of multiple weight loss steps can also
indicate the presence of multiple components in the
sample.
Tg of PMMA at different heating rate
155
Tg and Tm
156
10 oC/min
100
95
300 oC
Wt %
0
Time / temp
200 h
157
Modulus of different calss of polymers
w.r.t. temperature
158
Applications of Polymers
It is difficult to find an aspect of our lives that is not affected by polymers.
Just 70 years ago, materials we now take for granted were non-existent.
1.
2.
3.
4.
5.
6.
7.
8.
9.
Polymers in daily life:
Polymers in automotive
Polymers in sports
Polymers in agricultural
Polymers in medicine
Polymers pharmacy and pharmaceutical formulations
Polymers in aero-space
Polymers in electronics
Polymers in defence
159
Electronic Packaging
160
The need for low dielectric constant materials
• Smaller feature size in microelectronic devices leads to
increasing line to line capacitance
t = RC = 2  e e0 [4L2 / P2 + L2 / T2]
R
C

e
e0
L, P, T
161
= Total resistance
= Total Capacitance
= Specific resistance of the metal of the interconnect
lines.
= Dielectric constant of the insulator between the Inter
connect lines.
= Dielectric constants of vacuum.
= Length, pitch & thickness of the interconnect array.
Signal delay vs. device size in integrated circuitry
Ref: S.-P. Jeng et al. Mat. Res. Soc. Symp. Proc. 337, 25 (1994)].
162
SEMATECH roadmap for
intermetal dielectric
Required dielectric constant
Technology year
1998
2001
2004
2007
Design rule
(micron)
0.25
0.18
0.15
0.12
Required
e
3.9
2.9
2.3
1.9
Ref: Semiconductor Industry Association. International Technology Roadmap
for semiconductors (ITRS), 1998 update (http://www.itrs.net/ntrs/publntrs.nsf)
163
Book: Properties of Polymers, Fourth
Edition Their Correlation with Chemical
Structure their Numerical Estimation and
Prediction from Additive Group
Contributions
Authors: D.W. van Krevelen, Klaas te
Nijenhuis
O
SiO2 e = 4
164
KAPTON
O
O
N
N
O
O
e = 3.4
Tg > 300 0C
TS = 158 MPa
YM = 3.2 GPa
Water Absorption = 3.5 %
n
Properties required for new
intermetal Dielectrics
• Dielectric constant
< 3, preferably 2.5
• Dissipation factor at 1 MHz
< 0.005
• Thermal stability
400 - 450 0C
• Glass transition temperature
 300 0C
• Thermal conductivity
<0.5 W/(m.K)
• Coefficient thermal expansion
< 50 ppm
• Tensile strength
>100 MPa
• Young modulus
>1 GPa
• Moisture absorption
< 1%
• Good adhesion to materials such as SiO2, Si, Al, Cu, TiN
• Good film forming ability
Ref: P. Springer, Semiconductor. Int. 5 (1996) 88
165
Solutions
Spin-on
Plasma polymerization
• Well defined chemical structure
• Good local planarization
• Post deposition cure
• Solvent free
• Good uniformity
• Common equipment can be used
Concept
For low dielectric constant:
• Absence of polar groups
• Incorporation of fluorine as pendent CF3 group
For high Tg and strength:
• Stiff repeat unit
• High molecular weight
166
Spin-on
FLARE
F
F F
F
O
Ar
O
n
F
F F
e
Tg
Td
TS
YM
CTE
Gap Fill Property
167
F
= 2.5-3.1
= 189-285 oC
= 540 oC
= 83-107 MPa
= 2.45-2.95 GPa
= 65- 76 ppm / oC
= < 0.8 m
SiLK
Plasma polymerization
o
X
400-450 C
X
O
X =
S,
O,
H3C
CH3 F3C
C
168
C
,
C
CF3
e = 2.6 2.7
X
Plasma polymerization
Crosslinked BCB resins
OCH3
OCH3
Si
Si
O
OCH3
OCH3
T
OCH3
OCH3
Si
Si
O
OCH3
169
OCH3
e
TS
YM
CTE
Water
absorption
= 2.6-2.7
= 85 MPa
= 2 GPa
= 52 ppm / oC
= 0.2 %
Poly(perfluorocyclobutane) (PFCB)
F
F
F
CH3
O
F
C
F
O
F
O
F
Heat
F
F
FF
F
CH3
F
O
C
FF
F
O
FF
CH3
F
O
C
FO
FO
F
F
F
F
FF
F
F
FO
FF
F
F
O
C CH3
FF
FO
F
F
F
F
F
170
F
O
F
FF
FF
F
FF
e
= 2.35
Tg
= 400 oC
TS
= 66 MPa
YM
= 2.27 GPa
EB
=4%
Poor Thermal Stability
Plasma polymerization
Parylene F
F2C
F2C
e
Tg
Td
YM
CTE
171
CF2
600 oC
2
F2C
CF2
F2C
CF2
CF2
= 2.2-2.4
= 160 0C
= 530 0C
= 2.41 GPa
= 28 ppm / 0C
Designing new polymers by molecular engineering
F3 C
Polyamide/Polyimide
H 2N
O
Ar
O
NH2
CF3
F3 C
CF3
F
F
hbp
F
CF3
Ar
CF3
F3C
F
F3 C
Br
CF3
F3 C
F
F3 C
F
F3 C
F
HO
Polyether
hbp
F
B(OH)2
F
H 3C
F
CF3
OH
F3C
Polyether
F
F
F
O2N
H 3C
CF3
F3 C
O2N
O Y O
BrH2C
CH2Br
O
O
NO2
CF3
PPV derivative
F3 C
H 2N
O
Y
O
NH2
Polyamide/Polyimide
CF3
Courtesy of 5-bromo-2-fluoro benzotrifluoride
Spin-on
Poly(arylene ether)
CF3
O
O
n
F3C
e = 2.67; Td = 534 0C (5 % wt. loss in air)
Tg = 300 / 315 0C (DSC / DMTA)
TS = 75 MPa
Water absorption rate = 0.2 wt %
Ref : S. Banerjee, et al. Chem. Mater (1999)
173
Spin-on
Poly(ether imide)
e = 2.60;
Water abs. = 0.2 wt %;
Td = 526 0C; Tg = 273 0C;
Ts = 109 MPa ; Mod.= 2.5 GPa;
Eb = 24 %
Ref. S. Banerjee, et al. J. Polym. Sci. Polym. Chem. (2002)
174
n
Summary of the polymer properties
O
N
O
Ar
Q
CH3
Q
O
N
CH3
CH3
O
F3C
CH3
O
CH3
CF3
CF3
F3 C
F3C
CF3
O
CF3
262
12.94
3.12
0.45
252
20.59
2.79
0.28
239
11.57
3.09
0.48
230
11.72
3.05
0.53
268
23.05
2.92
0.21
260
30.56
2.52
0.18
245
20.86
2.62
0.28
235
21.09
2.57
0.26
311
11.36
2.81
0.48
285
18.55
2.58
0.38
282
10.29
2.92
0.51
275
10.41
2.90
0.47
CF3
CF3
O
Ar
% Water
abs.
O
CH3
CF3
%
Dielectric
Fluorine constant
CF3
CH3
CH3
Tg / 0C
O
CF3
CF3
O
CF3
F3C
CF3
O
O
Hyperbranched polymers
B
A
B
Schematic representation of a hyperbranched
polymer by AB2 monomer
[DBFréchet = (t+d)/(t+l+d)]
B
+
A
A
DB for linear polymer = 0
DB for hyperbranched polymer = 0-1
B
A
B
B
B
B
A
A
+
B
A
A
B
B
[DBFrey = 2d/(2d+l)]
DB for perfect dendrimer = 1
B
B
A
B
B
B
B
+
A
B'
A
B
A
A
B'
B'
B'
Schematic routes for hyperbranched polymers
Hyperbranched polymer
Concept
• Higher fractional free volume
• Higher fluorine content
11'
F3 C
8'
7'
6'
9
F
10
F3 C
3 5
5' 10'
8
4
6
NMP / toluene
O
K2CO3 / 180°C
CF3
7
11
2
4'
1'
2' 3'
1
5 10
6
OH
AB2
9'
F
9
7
8
F3 C
11
+
F
hb,n
hbp(lw) & hbp(hw)
R
HO
R
11'
OH
F3 C
R
O
8'
12
7'
A2
6'
15
17
5' 10'
R = CH3, CF3
NMP / toluene
O
4'
1'
K2CO3 / 180°C
R=
2' 3'
CH3
F3 C
11
Normalized heat flow (W/g)
endo up
O
16
R
13 14
9'
C
hbp(lw)
hbp(hw)
2a
2a
3a
1:1
3:2
2b
3b
3:2
7:6
2c
3c
2:1
4:4
100
2b
3a
AB2 / A2 OH / F
CF3
75
Weight %
3b
2c
3c
Td10% = 573 0C
Tg > 350 0C
Mw = 44,70,000 gmol-1
PDI = 2.2
2c
hbp(hw)
3c
50
25
0
50
100
150
200
250
o
Temperature C
300
350
0
100
200
300
400
500
600
700
800
O
Temperature C
A. Ghosh et.al. Macromolecules 2010
Energy Saving
178
Membrane Based Separation Processes
Process
Pore size/ mol wt
Driving Force
Mechanism
Advantages
Microfiltration
0.02-10μm
ΔP 0-1 bar
Sieving
• Low energy consumption.
Ultrafiltration
0.001-0.02μm
mol wt 103-106
ΔP 0-10 bar
Sieving
• Low investment cost.
Nanofiltration
<2 nm
mol wt 102-103
ΔP 10-25 bar
Solution Diffusion
Reverse
Osmosis
non porous
ΔP 10-100 bar
Solution Diffusion
Gas Separation
non porous
ΔP 10-100 bar
Solution Diffusion
Dialysis
10-30 A
Concentration
difference
Sieving plus Diffusion
Pervaporation
non porous
Partial pressure
difference
Solution Diffusion
Electrical potential
Ion Migration
Electrodialysis
mol wt <200
• Better selectivity without thermodynamic limitations.
• Clean and close operation.
• No process wastes.
• Compact and scalable units.
Drawbacks
• Scarce membrane market.
• Lack of information.
• Low permeate flows.
• Limited application
1. Sorption
Organic substances
dehydration
2. Diffusion
3. Desorption
Recovery of volatile
compounds at low
concentrations
Separation of close
boiling as well as
azeotropic mixtures
Polyimides
Kapton®
Strengths
 High thermal stability
 High glass transition temperatures
(above 350 oC)
 High mechanical properties
 Good chemical resistance
 Low dielectric constant
Ref. H. Ohya, V.V. Kudryavtsev, S.I. Semenova, Polyimide membranes: Applications,
fabrications, and properties. Gordon and Breach, Tokyo, 1996.
Industrial Applications
Insulating films for flexible cables in
electrical industry
High temperature adhesive in semiconductor
industry
High temperature resistive cables for
aerospace application
Machinery parts and shapes for automobile
application
Photoresist material in photolithography
Membrane based gas separation application
Ref. N.L. Norman, G.F. Anthony, W.S. Winston Ho, Advanced membrane technology
and applications. John Wiley & Sons Inc; 2008.
Scope of gas separation process
 Recovery of excessive flue gases from
heavy industries effluents.
 Removal of CO2, H2S and H2O from natural
gas to increase the fuel efficiency and decrease
pipe corrosion.
 Preparation of oxygen enriched air.
Other technologies
 Amine adsorption process
Cryogenic distillation process
Gas Separation Membrane Market Value, 2000
Total Value : $127 mililion
Ref. F.P. McCandless, Ind. Eng. Chem. Process Des. Dev. 1972, 11, 470.
W.J. Koros, G. K. Fleming, J. Membr. Sci. 1993, 83, 1.
Commercially Used Polymers for Gas Separation
Permeability
(Barrers)
Polymer
O
O
Ideal
permselectivity
α (CO2/CH4)
Ideal
permselectivity
α (O2/N2)
CO2
O2
9.0
1.90
37.5
7.0
1.33
0.41
36.9
8.0
3.28
0.81
25.2
6.2
5.6
1.4
22.4
5.6
6.56
1.46
32.8
6.4
O
N
N
O
n
O
Matrimid
O
O
O
O
N
N
O
n
O
Ultem
O
O
O
O
N
O
S
O
N
O
O
n
Extem
O
O
O
S
O
Polysulfone
H3COCOH2C
O
O
OH
n
H3COCO
Cellulose acetate
n
Ref. T.S. Chung et al., Ind. Eng. Chem. Res. 10.1021/ie901906p
A.C. Puleo, D.R. Paul, Journal of Membrane Science, 47 (1989) 301.
Design concept
Solution diffusion mechanism
Fixed
O
N
O
G. Maier, Angew. Chem. Int. Ed.
1998, 37, 2960.
O
Ar' N
O
O
F3C
Ar
CF3
O
O
N
O
O
Ar' N
O
O
O
N
O
Matrimid® 5218 Resin
O
Scope of membrane research
N
O n
CO2 recovery from land fill gas
CO2 ~ 40-45 mol %
CH4 ~ 54 – 59 mol %
N2 ~ 4 %, O2 ~ 1 %
Water vapor ~ 1 %
H2S & CFC ~ trace
Capture of CO2 from the flue gas
(CO2 ~ 15 %, water ~ 7 %, O2 ~ 3 %, Nitrogen ~74 %, NOx
+ SOx ~ 1 %)
Commercial membranes are limited to ambient
temperature
 Matrimid offers high temperature separation of
CO2
 Mixed matrix membranes CMS dispersed within
polymer matrices showed manifold increase in CO2
permeability and CO2 / CH4 selectivity
Present need:
 Membrane that can operate at high temperature
and pressure
 Higher flux and selectivity
 Low cost (for large scale application)
Measurement of Gas Transport Properties
CO2
CH4
Figure: Schematic diagramme of the instrumental setup
P = Permeability coefficient
V = downstream volume
(119 cm3)
D = Diffusion coefficient (cm2/sec)
A = area of membrane
(5.069 cm2 )
O2
pi = upstream gas pressure
(3.5 atm.)
αA/B = Ideal permselectivity
towards gas ‘A’ relative to gas ‘B’
T0 = 273 K , p0 = 1atm.
T = experimental temperature
d = thickness of membrane
1 Barrer = 10 -10 cm3 (STP) cm/cm2 s cm Hg
N2
Calculation of Gas Transport Coefficients
(dp/dt)s = downstream pressure increment
per unit time at steady state
θ
= time-lag
dp
dt
θ
Where we stand?
Membrane type
Permeability (barrers)
Structure
O
CF3
BAPY-6FDA
O
O
N
F3 C
N
CF3
1.95
26.6
51.91
2.11
24.6
52.98
1.21
43.8
53.85
1.01
53.3
O
O
F3 C
CH3
O
O
F3 C
O
CF3
N
N
n
O
CH3
H 3C
SBPDA-6FDA
51.92
n
O
H3C
CH4
O
CF3
N
F3 C
BPI-6FDA
CO2
Ideal selectivity
P(CO2)/P(CH4)
CH3
O
F3 C
O
F3 C
O
CF3
O
O
N
N
n
F3 C
H 3C
O
CH3
O
O
N
CF3
BAPA-6FDA
O
O
O
F3 C
O
CF3
N
N
n
O
F3 C
O
CF3
BIDA-6FDA
O
O
N
O
F3C
CF3
O
N
n
O
N
O
F3 C
O
O
71.32
1.99
35.8
S. K. Sen, Banerjee et al., J. Membr. Sci. Vol. Vol. 343, pages 97-103(2009)
S. K. Sen, Banerjee et al., J. Membr. Sci. Vol. 350, pages 53-61 (2010)
B. Dasgupta , Banerjee et al., J. Membr. Sci. Vol. 345, pages 249-256 (2009)
A. Bos et al., Sep Purif Technol. 1998, 14, 27;
W. J. Koros et al., J. Membr. Sci. 2008, 175, 181;
and H. Yamamoto et al., J. Polym. Sci. Part B: Polym. Phys. 1990, 28, 2291.
P(CO2)/P(CH4)
Comparison of CO2/CH4 Separation Performances with
Commercially Used Polymers
1000
Matrimid
100
10
0.1
Ultem
Extem
Polysulfone
Cellulose acetate
BAPA-PMDA
BAPA-6FDA
BAPA-BTDA
BAPA-ODPA
BAPA-BPADA
SBPDA-BPADA
SBPDA-6FDA
SBPDA-ODPA
BAQP-6FDA
BATP-6FDA
BAPy-6FDA
BATh-6FDA
BIDA-BPADA
BIDA-6FDA
BIDA-BTDA
BIDA-ODPA
1
Present Upper Bound
10
P(CO2) in Barrers
100
Comparison of O2/N2 Separation Performances with
Commercially Used Polymers
P(O2)/P(N2)
100
10
1
0.01
Matrimid
Ultem
Extem
Polysulfone
Cellulose acetate
BAPA-PMDA
BAPA-6FDA
BAPA-BTDA
BAPA-ODPA
BAPA-BPADA
SBPDA-BPADA
SBPDA-6FDA
SBPDA-ODPA
BAQP-6FDA
BATP-6FDA
BAPy-6FDA
BATh-6FDA
BIDA-BPADA
BIDA-6FDA
BIDA-BTDA
BIDA-ODPA
0.1
Present Upper Bound
1
P (O2) in Barrers
10
100
Sulzer Chemtech AG, P.O. Box 65
CH-8404, Winterthur, Switzerland
BORSIG Membrane Technology GmbH
Egellsstraße 21, 13507 Berlin, Germany
Betheniville, France
H
Pervaporation
H
Why Benzene/Cyclohexane?
H
H
 Industrial demand
 Close boiling mixtures
 Form azeotropes
 Easily detected by GC
H
H
H
H
H
H
H
bp (0C): 80.100
fp (0C): 5.533
H
H
H
H
H
H
H
bp (0C): 80.738
fp (0C): 6.554
Bz + Cy (45 wt%): bp 77.5 (0C)
Different polymers used for Benzene/Cyclohexane
Membrane
Benzene
in feed
Temperature
(0C)
Normalized Flux (J)
(kg μm/m2h)
Separation factor
(α)
Reference
LDPE
50
25
10.8
1.6
Huang et al 1968
PVDF
53
56
1.5
5.4
McCandless et al 1974
PVA/PAAm
50
25
2.3
11.9
Park et al 1994
Modified nylon 6
50
50
0.057
4.5
Yoshikawa et al 1997
PAS
50
50
2.6
22.5
Ray et al 1997
PU-TEOS
50
50
0.65
19
Kusakabe et al 1998
BAPPP-TIPA
50
50
16.3
4.9
Wang et al 2001
BAPPH-TIPA
50
50
29.4
4
Wang et al 2001
LDPE: Low density polyethylene; PVDF: Poly(vinylidene fluoride); PVA/PPAm: Polyvinyl alcohal/ Polyallyl amine; PAS:
Poly(acrylonitrile-co-styrene); PU-TEOS: Polyurethane-tetraethyl-ortho-silicate); BAPPP: 2,2-Bis[4-(4-amionphenoxy)
phenyl]propane; BAPPH: 2,2-Bis[4-(4-amionphenoxy)phenyl]hexafluoro propane; TIPA: 5-t-butyl-isophthalic acid.
H
Why Benzene/Cyclohexane?
 Industrial demand
 Close boiling mixtures
 Form azeotropes
 Easily detected by GC
H
H
H
H
H
H
bp (0C): 80.100
fp (0C): 5.533
Benzene
H
H
H
H
H
H
H
H
H
bp (0C): 80.738
fp (0C): 6.554
Bz + Cy (45 wt%): bp 77.5 (0C)
Ethyl benzene
Cumene
Cyclohexane
Aniline
Chlorobenzenes
Styrene
Adipic acid
Caprolactam
Polystyrene
Nylon 6,6
Nylon 6
Polycarbonate
Bisphenol A
Acetone
H
Epoxy resins
Phenol
Phenolic resin
H
Goal of the present research
 Design and preparation of new diamine monomers
 Preparation of processable PEAs
 Systematic investigation of pervaporation study of
the PEAs for benzene (Bz)/cyclohexane (Chx) mixture
at different temperatures (50, 60 and 70 oC)
 Establishment of structure property correlationship
Pervaporation application
 10% OV-17
packed column
 Flame ionization
detector (FID)
 Temperature of
the oven, injector
and detector 80,
100 and 200 oC
Chx
Bz
Bz
Chx
Polymer Structure vs. Properties
PEAs
X
FFV
Separation
factor (α)
Normalized flux
(kg.μm/m2.h) at 50 oC
250
0.188
4.7
23.66
2087
252
0.287
4.4
29.89
2421
273
0.293
3.9
31.42
2169
310
0.254
5.9
30.85
3601
233
0.143
6.9
13.41
1888
240
0.176
6.5
21.77
2849
294
0.173
5.9
23.91
2788
300
0.145
7.6
23.03
3616
230
0.167
6.2
18.04
2236
233
0.201
5.7
24.86
2782
285
0.199
5.0
27.31
2600
290
0.168
7.1
26.04
3782
Ar
-(CH3)2120 o
Tg (oC)
-(CF3)2-
(a)
a
PSI (g/m2.h)
at 50 oC
O
N
-(CH3)2180 o
-(CF3)2-
(b)
120 o
b
-(CH3)2-(CF3)2-
(c)
c
O
N
100
Pervaporation performances in comparison with
commercially used polymers
Separation factor (a)
O
10
1
0.01
PVA; 27 C
O
PUU; 25 C
O
PEA; 50 C
O
CD/PU; 25 C
O
PEA-Ia; 50 C
O
PEA-IIa; 50 C
O
PEA-IIIa; 50 C
O
PEA-IVa; 50 C
O
PEA-Ib; 50 C
O
PEA-IIb; 50 C
O
PEA-IIIb; 50 C
O
PEA-IVB; 50 C
O
PEA-Ic; 50 C
O
PEA-IIc; 50 C
O
PEA-IIIc; 50 C
O
PEA-IVc; 50 C
0.1
Upper bound trade-off curve
Lue and Peng, 2003
1
10
100
2
Normalized flux (kg.m/m .h)
1000
Renewable Energies
198
Conjugated polymers
Conductive polymers or, more precisely, intrinsically conducting polymers
(ICPs) are organic polymers that conduct electricity
1. Conjugated organic polymers can be doped, via oxidation or reduction
chemistry or via acidbase chemistry, to induce very high electrical
conductivity.
2. Conjugated polymers are beginning to fnd uses, in both the neutral
and the doped states, in prototype molecular-based electronics
applications and in electronic and opto-electronic devices.
199
Two conditions to become conductive:
1. The first condition for this is that the polymer consists of alternating
single and double bonds, called conjugated double bonds. In
conjugation, the bonds between the carbon atoms are alternately single
and double. Every bond contains a localised “sigma” (σ) bond which
forms a strong chemical bond. In addition, every double bond also
contains a less strongly localised “pi” (π) bond which is weaker.
2. The second condition is that the plastic has to be disturbed - either by
removing electrons from (oxidation), or inserting them into (reduction),
the material. The process is known as doping.
200
Discovery of conducting polymers
1862
Lethby (College of London Hospital)
Oxidation of aniline in sulfuric acid
1970’s
Shirakawa (Japan)
Acetylene gas
CH
Ti(OBu)4 & Et3Al
Toluene
Ti(OBu)4 & Et3Al
Hexadecane
–78oC
150oC
copper-coloured film
cis-polyacetylene
201
HC
silvery film
trans-polyacetylene
Discoverers - Nobel Prize 2000
A. Heeger, A. McDiarmid, H. Shirakawa
202
Polyacetylene (PA)
n
n
Electrical conductivity (s)
cis PA
trans PA
10-10 – 10-9 S cm-1
10-5 – 10-4 S cm-1
For comparison : s (copper)
: s (teflon)
203
~ 106 S cm-1
~ 10-15 S cm-1
Doping leads to enhanced conductivity
Semiconductor
s ~ 10-5 S cm-1
n
- e-
+ e-
Oxidation
-
+
n
Metal
s ~ 104 S cm-1
204
Reduction
n
Electrical conductivities
Copper
Platinum
Bismuth
Graphite
Doped polyacetylene is, e.g.,
comparable to good conductors such as
copper and silver, whereas in its original
form it is a semiconductor.
10+6
10+4
10+2
100
Germanium
Silicon
Polymers
10-2
10-4
10-6
Polyethylene
10-8
10-10
10-12
Diamond
10-14
10-16
Quartz
-1
10-18 S cm
The game offers a simple model of a doped
polymer. The pieces cannot move unless there
is at least one empty "hole". In the polymer each
piece is an electron that jumps to a hole vacated
by another one. This creates a movement along
the molecule - an electric current
205
Examples of conducting polymers
H
H
Polyaniline
(PANI)
Polypyrrole
(PPy)
Polyethylene
dioxythiophene
(PEDOT)
O
N
N
Polythiophene
(PT)
n
N
O
S
Polyparaphenylene
vinylene
(PPV)
N
N
n
S
Polyparaphenylene
(PPP)
n
n
Alkoxy-substituted
polyparaphenylene
vinylene
(MEH-PPV)
O
n
n
O
206
n
Polyacetylene - electronic structure
-electronic energy levels and electron occupation
(a)
(a) ethylene
(b) allyl radical
(c) butadiene
207
(b)
(c)
(d)
(d) regular trans-PA
(e) dimerised trans-PA
(e)
208
p Orbitals
+
_
*
p

atom
diatomic molecule
……
* band
 band
extended molecule
 bonds
Bonding combination of p orbitals ()
electron density builds up
between the nuclei
Antibonding combination of p orbitals (*)
The wavefunctions cancel between
the nuclei.
Larger molecules
To generate the molecular
orbitals of larger
molecules, we take linear
combinations of the atomic
orbitals from each atom. If
there are n atoms, there
will be n different
combinations. With a little
bit of math, the energy
levels and wave functions
to the right can be found.
butadiene
fully
antibonding
3 nodes
partially
antibonding
2 nodes
partially
bonding
1 node
fully bonding
0 nodes
Top down view
of the p orbitals
Atkins, Physical Chemistry
Benzene
The  electrons
The s electrons
Top down view
of the p orbitals
Atkins, Physical Chemistry
 Conjugated polymers
PA: polyacetylene
(1st conducting polymer)
PPV: poly(phenylene-vinylene)
(used in 1st polymer LED)
n
S
PT: polythiophene
(widely used in transistors)
S
n
PPP: poly(para-phenylene)
(large bandgap)
n
Band diagram for poly(para-phenylene)
Benzene
levels
n
PPP
Eg
-/a
0
/a
k
E.K. Miller et al., Phys. Rev. B, 60 (1999) p. 8028.
Tuning the bandgap of conjugated polymers
~ 3 eV
~ 2 eV
Tuning the bandgap of polythiophene derivatives
which one has the largest
bandgap?
Mats Andersson et al. J. Mater. Chem., 9 (1999) p. 1933.
How to make conjugated polymers:
1. precursor methods
The Durham precursor route to polyacetylene.
The Wessling-Zimmermann route to PPV.
water-soluble polyelectrolyte
Feast et al. Polymer 37 (1996) p. 5017.
Synthesis of PPV
Synthesis of Soluble PPV
CH3O
i. NaOH / MeOH
OH
CH3O
O
ii. Br
Dioxane
30% Formaline
dry HCL
ClCH2
O
THF
CH3O
O
CH2Cl
CH3O
Potassium tert. butoxide
n
/ HCl
Different forms of PANI
Oxidative polymerization of thiophene
Electrochemical mechanism
How to make conjugated polymers:
2. polycondensation
X
X
Y
Commonly Used Coupling
Reactions
• Stille Coupling
• Suzuki Coupling
• Heck Reaction
• Ullmann Reaction
• Sonogashira Coupling
• Kumada and Negishi Coupling
Y
[
]
n
Stille Coupling
Pd(II)L2Cl2 + 2R’SnBu3
R-R’
3. Reductive
Elimination
R’-R’ + 2Bu3SnCl
Pd(0)L2
1. Oxidative
addition
RX
RPdL2R’
2. Transmetalation
Bu3SnX
RPdL2X
R’SnBu3
Suzuki Coupling
Ullmann Reaction
Heck Reaction
Sonogashira Coupling
http://www.organic-chemistry.org
Pd(0)
n (HO)2B
B(OH)2
+
n Br
Br
n
226
Negishi Coupling
Kumada Coupling
Different approaches to one polymer
n-type doping
Energy
e-
Lithium
Polymer
Reducing agents donate electrons to the conduction band.
Solids like calcium, lithium and sodium tend to dope the polymer only near the
surface since they cannot diffuse into the film. Electrolytes (see below) can be
used to dope an entire film.
(-polymer)n + (Na+(Naphthalide)-]y -> [(Na+)y(-polymer)-y]n + y(Naphth)0
Counter-ion
Reduced
polymer
Oxidized
molecule
p-type doping
Polyethylene dioxythiophene polystyrene sulphonate (PEDOT/PSS) can be
bought from Bayer as an aqueous solution under the trade name Baytron.
PEDOT
PSS
The sulphonic acid group on the PSS dopes the PEDOT to make it conductive.
The Nobel Prize in Chemistry 2000
Small conjugated molecules
anthracene
tetracene
It is not impossible to solution deposit
small molecules, but it is usually hard
to make high quality films because
the solution viscosity is too low.
Small molecules are usually
deposited from the vapor phase.
Mobilities of >1 cm2/V-s can be
achieved by thermally evaporating
thin films. The mobility is limited by
grain boundaries.
Mobilities > 3 cm2/Vs can be
achieved by growing single crystals.
pentacene
Thermal evaporation of small molecules
Substrate
The pressure is low enough for the mean
free path of a molecule to be larger than the
size of the chamber.
Shutter
Impurities with a higher vapor pressure than
the desired molecule are deposited on the
shutter.
q
Host
Heater
Dopant
Pump
Peter Peumans
Depositing polymers: Spin coating
Procedure
1. Dissolve the material.
2. Cast the solution onto the substrate.
3. Spin the substrate at 1000 to 6000 revolutions per
minute.
Most (~ 99 %) of the solution is flung off of the
substrate, but a high-quality thin film is left behind.
The thickness of the films goes up with increasing
solution concentration and down with increasing spin
speed. Polymers with larger molecular weights tend to
result in more viscous solutions, which yield thicker
films.
Features of spin coating
Advantages
• Spin coating can be done at atmospheric pressure and is very cheap.
• Film thickness of up to several hundred nanometers can be obtained.
• The thickness can be controlled (but not as well as with evaporation).
• The thickness is fairly uniform across the substrate (except at the edge).
Disadvantages
• The whole substrate is coated. Patterning must be done separately.
• In most cases, part of the material must be nonconjugated so that the
molecules are soluble.
• In can be difficult to make multilayer structures because the deposition of
one layer can dissolve the layer underneath.
Screen printing
• This technique is used to put patterns on T-shirts.
• The squeegee is used to press the dye through the screen.
• Recently screen printing of polymers has been used to make LEDs
and photovoltaic cells.
This LED doesn’t have perfectly uniform emission, but it isn’t bad
for the first demonstration of this deposition method.
Ghassan Jabbour et al. Adv. Mater. 12 (2000) p. 1249.
Advantages and disadvantages of screen printing
Advantages
• Large areas can be covered at low cost.
• Atmospheric pressure.
• Patterning is possible.
Disadvantages
• Controlling film thickness might be difficult.
• The material must be soluble and have a
viscosity within a certain range.
Drop casting
Drying solution that leaves
a film behind.
Petri Dish
Substrate
Hotplate
Covering the sample with a Petri dish slows down the evaporation rate,
which results in more uniform films.
Keeping the substrate level results in much more uniform films.
Since the solvent evaporates slowly, the material can crystallize or aggregate into
fairly well ordered structures. (This can be good or bad.)
Summary of drop casting
Advantages
• Film thickness can be far greater than 1 m.
• This method is very inexpensive.
• In many cases the film can be removed from the
substrate by peeling or by dissolving the substrate
(which would be NaCl or KBr).
Disadvantages
• The film thickness is difficult to control and is not
very uniform.
• Very thin films are difficult to make.
• The material must be soluble.
Ink Jet Printing (IJP)
Polymers can be deposited from a printer onto a substrate.
Advantages
• Patterning with resolution approaching 5-10 m is possible.
• No material is wasted. (~ 99 % is wasted with spin casting)
• Cost can be extremely low
Disadvantages
• Controlling film thickness is difficult.
• Fabrication of multilayer structure is difficult (compared to evaporation)
Conducting Mechanism
241
How does a conducting polymer work ?
Oxidative doping of polyacetylene by iodine
[CH]nx+ + xI3-
[CH]n + (3x/2) I2
+
.
I 3-
+
Polaron and its delocalisation
.
I3 -
+
.
I 3Oxidation with iodine causes the electrons to be jerked out of the polymer, leaving "holes"
in the form of positive charges that can move along the chain.
242
Excitations
Bipolaron
+
.
oxidation
+
+
Neutral Soliton
isomerisation
.
Positive Soliton
oxidation
243
+
244
Applications of conducting polymers
Polyaniline (PANI)
Transparent conducting electrodes
Electromagnetic shield
Corrosion inhibitor
‘Smart windows’ (electrochromism)
Polypyrrole (Ppy)
Radar-invisible screen coating
(microwave absorption)
Sensor (active layer)
Polythiophene (PT)
Field-effect transistor
Anti-static coating
Hole injecting electrode in OLED
Polyphenylenevinylene (PPV)
Active layer in OLED
245
Organic light emitting diodes (OLED’s)
An OLED is any light emitting diode (LED) which emissive
electroluminescent layer is composed of a film of organic compounds.
•
A light emitting polymer is an electro-luminescent plastic. The molecules of this
plastic emit light when an electric field is applied.
•
Polymer based light-emitting diodes (LED) were discovered in 1990.
•
Cambridge Display Technology has the core patents for the Technology of LEP.
Flexible plastic
serves as home to
new, highly
efficient organic
light-emitting
diodes.
OLEDs provide high-contrast and low-energy displays that are rapidly
becoming the dominant technology for advanced electronic screens.
246
OLED Structure
Electric field
Metal electrode
Organic thin film
+
Transparent
electrode (ITO)
An OLED consists of the following parts:
Light
1. Substrate (clear plastic, glass, foil) - The substrate supports the OLED.
2. Anode (transparent) - The anode removes electrons (adds electron
"holes") when a current flows through the device.
3. Conducting layer - This layer is made of organic plastic molecules that
transport "holes" from the anode. One conducting polymer used in OLEDs
is polyaniline.
4. Emissive layer - This layer is made of organic plastic molecules
(different ones from the conducting layer) that transport electrons from the
cathode; this is where light is made. One polymer used in the emissive
layer is polyfluorene.
5. Cathode (may or may not be transparent depending on the type of
OLED) - The cathode injects electrons when a current flows through the
device.
247
OLED Operation
• A typical OLED is composed of a layer of organic materials situated between two electrodes, the
anode and cathode, all deposited on a substrate. The organic molecules are electrically conductive
as a result of delocalization of pi electrons caused by conjugation over all or part of the molecule
•During operation, a voltage is applied across the OLED such that the anode is positive with respect to
the cathode.
• A current of electrons flows through the device from cathode to anode, as electrons are injected into
the LUMO of the organic layer at the cathode and withdrawn from the HOMO at the anode.
• This latter process may also be described as the injection of electron holes into the HOMO.
• Electrostatic forces bring the electrons and the holes towards each other and they recombine forming
an exciton, a bound state of the electron and hole.
• This happens closer to the emissive layer, because in organic semiconductors holes are generally
more mobile than electrons.
•The decay of this excited state results in a relaxation of the energy levels of the electron,
accompanied by emission of radiation whose frequency is in the visible region.
•The frequency of this radiation depends on the band gap of the material, in this case the difference in
energy between the HOMO and LUMO.
248
249
Principle of EL
eLUMO
LUMO
h+
HOMO
Cathode
HOMO
Anode
Light
Polymers for Organic Light Emitting
Diodes (OLED)
O
n
PPV
n
O
MEH-PPV
Commercial materials like Mn2+ in ZnS require 100V DC
PPV : requires 5 - 10V DC
runs even with AC
brightness ~40,000 cd/m2 ie. ~100 times brighter than a TV screen
252
253
254
255
Renewable Technologies: Need
• It is expected that the global energy demand will double within the next 50 years.
• Fossil fuels are running out and are held responsible for the increased
concentration of carbon dioxide in the earth’s atmosphere.
• Hence, developing environmentally friendly renewable energy is one of
the challenges to society in the 21st century.
• One of the renewable technologies is the hydrogen fuel cell that generates
electricity from the chemical reaction of hydrogen and oxygen as a byproduct water.
• Similarely photovoltaics (PV), is the other renewable energy technologies is
the technology that directly converts daylight into electricity.
• Thus, hydrogen fuel cells and photovoltaic (PV) energy technologies can
contribute to environmentally friendly renewable energy production and mitigate
the issues associated to carbon dioxide emission……Global warming!!!
256
257
Molecular structures of the conjugated polymers transpolyacetylene (PA), poly(pphenylenevinylene) (PPV), and
a substituted PPV (MDMO-PPV)
258
Basic processes in an organic solar cell
Various architectures for organic solar cells have been investigated in recent
years. In general, for a successful organic photovoltaic cell four important
processes have to be optimized to obtain a high conversion efficiency of solar
energy into electrical energy.
-Absorption of light
-Charge transfer and separation of the opposite charges
-Charge transport
- Charge collection
For an efficient collection of photons, the absorption spectrum of the
photoactive organic layer should match the solar emission spectrum and the
layer should be sufficiently thick to absorb all incident light. A better overlap
with the solar emission spectrum is obtained by lowering the band gap of the
organic material.
259
260
The need for two semiconductors:
Photovoltaic cell configurations based on organic materials differ from those
based on inorganic semiconductors, because the physical properties of inorganic
and organic semiconductors are significantly different.
• Lower dielectric constant
• Exciton binding energy is larger than inorganic semiconductors energy
(for GaAs the exciton binding energy is 4 meV, for polydiacetylene 0.5
eV)
• Dissociation into free charge carriers does not occur at room
temperature in case of organic conducting polymers. Hence, low
mobility of the charge carriers and the internal field of the p-n junction.
Both p-type (donar) and n-type (acceptor) material is
required for organic PV technology
261
262
263
264
Schematic drawing of the working principle of
organic photovoltaic cell
265
266
Bulk-heterojunction solar cells
Power conversion efficiencies exceeding 2.5%
(MDMO-PPV as a donor and PCBM as an acceptor)
267
The bulk-heterojunction concept.
268
269
270
ITO substrate
Pattern
generated
in
Aqua regia
PEDOT PSS layer
Spin coated
Polymer +PCBM
deposition
by spin coating
Deposition of metal
cathodes by
thermal evaporation
BHJ
PEDOT
PSS layer
Spin coated
V
Bilayer
V
polymer layer
Spin coated
271
PCBM layer
Spin coated
Deposition of metal
cathodes by
thermal evaporation
272
273
165,000 TW of sunlight
hit the earth
274
275
276
277
278
Optimizations at Spatial Domain
279
280
281
282
BTFM-PPV
BTFM/MEH-PPV
DBTFM-PPV
F
F
F
CF3
CF3
CF3
OCH3
O
283
n
O
x
n
y
O
F3C
F
Introduction
The global energy demand expected to be double within
the next 30-40 years
90% of present global energy is supplied by fossil fuels
•Non-sustainable
•Negative environmental impacts
Need sustainable, environmentally-friendly energy
sources
Fuel cells are a promising technology
Introduction
 PEMFCs are considered as reliable alternate
energy converting device because of







high power density
high efficiency
low operating temperatures
solid non-corrosive electrolyte
long life
ease of design and adaptable size
environmentally friendly
 Polymer electrolyte membranes (PEMs) are key
materials for proton exchange membrane fuel
cells (PEMFCs)
 Applications:
 Automobiles
 portable devices
 Stationary systems
Working Principle of PEMFC
1.
When hydrogen is lead to the first catalyst layer, at
anode, the hydrogen molecules are split into
their basic elements, i.e. protons and electrons.
2.
The protons migrate through the electrolyte
membrane to the second catalyst layer, the cathode.
Here they react with oxygen to form water.
3.
At the same time the electrons are forced to travel
through external circuit to the cathode side, because
they can not pass the membrane
4.
This movement of electrons thus creates an electrical
current
Electrode reaction:
Anode: H2
2 H+ + 2 e-
Cathode: ½ O2 + 2 H+ + 2 eOverall: 2H2 + ½ O2
catalyst
H2O
H2O
Proton transport mechanism
 “Grotthus mechanism”
•Protons hop from one hydrolyzed ionic site (SO3¯H3O+ ) to another across
the membrane
• It involves conversion of H-bonds to covalent bonds between water
molecules and vice versa; only the charge of the proton is transported and
not its mass.
 “Vehicular mechanism”
•
Hydrated proton (H3O+) diffuses through the aqueous medium in
response to the electrochemical difference
•
The water connected protons (H+ (H2O)x) in the result of the electroosmotic drag carry the one or, more molecules of water through the
membrane and itself are transferred with them.
Scope of the Work
 Required and desirable characteristics






High ionic conductivity (and zero electronic conductivity)
Good mechanical strength
Long-term chemical stability i.e. good oxidative and hydrolytic stability
Good thermal stability
Low oxidant and fuel cross-over
Low cost and ready availability
 DuPont's Nafion®: A state of art PEM material for fuel cell
Nafion®117 : m ≥1, n=2, y=1, x=7-20
Advantage:
Disadvantage:
 Excellent Proton Conductivity up to
10-2-10-1 S/cm
 Good chemical & oxidative stability
 Long term stability
 Expensive (up to US$ 700 per
square meter).
Nafion®
 High methanol permeability
 Loss of membrane performance at
elevated temperature (>80 oC)
 The current state-of-the-art performance is not high enough for the practical applications
Why does Nafion® possess high proton conductivity?
 nano scale phase separation between
hydrophilic and hydrophobic domains
 connectivity between the hydrophilic domains
Hydrocarbon based alternative PEM materials
Sulfonated PEEK
Sulfonated Polyimide
Sulfoarylated PBI
Sulfonated Poly(arylene ether sulfone)
Sulfonated Poly[(3methylphenoxy)(phenoxy)phosphazene]
HO
OH
A
A
n
n
n
n
B
0.1n
0.2n
0.3n
0.4n
C
0.9n
0.8n
0.7n
0.6n
O
Cl
S
Cl
O
B
HO3S
SO3H
O
Cl
S
C
Cl
O
291
General understanding about hydrocarbon
based PEM materials
Increase in IEC results in increase in proton conductivity.
A trade-off relation exists between IEC and stability related
properties (like dimensional stability, hydrolytic- oxidative
stability) & also with mechanical strength.
Control of polymer morphology and ionic nanostructure is
effective to obtain PEMs which have moderate IEC values
and high proton conductivity.
Methodologies to obtain desired properties
 Introduction of polar and flexible ether linkages to
have better solubility & processability.
 Inclusion of hydrophobic pendant -CF3 groups to
have better phase separated morphology and
stability.
 Copolymerization
properties.
to
control
IEC
and
other
Synthesis of semifluorinated 5-Membered SPIs
HO3S
H2 N
Scheme :
NH2
SO3H
DSDSA
Synthesis of diamine monomer
N(CH2CH3)3
N2 flow
H2N
X
NH2
+
m-cresol/ 80oC
+
H2N
O
NH2
SO3H N+
QA
O
O
H N- +
O3 S
O
O
O
O
O
BPADA
N2 flow
m-cresol/ 800C /4 hr
Sulfonated polyamic acid as triethylammonium sulfate form
N2 flow
Quadri diamine(QA)
1800 C/ 16 hr
2000C/ 4 hr
-(m+n) H2O
O
* N
Ref: S. Banerjee et al. / Polymer 44 (2003) 613–622
O
N
N
X
O
O
N
N
X
H N+
O3 S
*
SO3N+ H
m
O
O
1-m O
O
O
N
O
O
O
O
O
Acid treatment
Yield= 99 %
* N
O
1-m O
O
O
O
O
O
O
O
N
O
HO3S
SO3H
*
m
Sulfonated Polyimide
CF3
X=
O
O
F3C
E.A. Mistri, A.K Mohanty, S. Banerjee / Journal of Membrane Science 411– 412 (2012) 117– 129
m = 0.5, (DSDSA/QA)
= 0.6, (DSDSA/QA)
= 0.7, (DSDSA/QA)
= 0.8, (DSDSA/QA)
= 0.9, (DSDSA/QA)
= 1.0, (DSDSA/QA)
= 50/50
= 60/40
= 70/30
= 80/20
= 90/10
= 100/0
Good thermo-mechanical properties
70
100
DRY Membranes
60
Tensile stress (MPa)
Weight (%)
80
60
DQB50
DQB60
DQB70
DQB80
DQB90
DQB100
40
20
50
40
30
DQB50
DQB60
DQB70
DQB80
DQB90
DQB100
20
10
0
0
0
100
200
300
400
500
600
700
800
900
0
5
Temperature (oC)
10
15
20
25
Tensile strain (%)
TGA plots of the SPIs; heating rate: 10 oC min−1
(Stress-strain plot of DQB membranes;
strain rate 5%/min, at 25 oC and 65% RH)
 Initial weight loss ~ 100 ºC
evaporation of the absorbed water.
nd
 2 weight loss ~ 285 ºC
decomposition of sulfonic acid groups.
 3rd weight loss around 580 ºC -600 ºC
pyrolysis of the SPI backbones.
 Good mechanical properties (tensile strength
ranging from 42 – 66 MPa and Young’s moduli of
1.45–1.67GPa).
Microstructure, IEC & proton conductivity
DQB 50
DQB 80
DQB 70
DQB 60
TEM micrographs of SPI membranes (cross section, Ag+ form)
Polymer
membranes
DSDSA
mole %
IEC
(meq/g)
Theo.
Exp.
WU
(wt %)
Proton
conductivity
(S.cm-1)
DQB50
50
1.00
0.96
14.0
3.96×10-3
DQB60
60
1.24
1.19
20.55
1.07×10-2
DQB70
70
1.49
1.42
25.29
1.47×10-2
DQB80
80
1.75
1.65
30.0
2.09×10-2
DQB90
90
2.04
1.93
35.17
3.45×10-2
DQB100
100
2.34
2.20
41.27
–
Proton conductivity, s (mS/cm)
 PEM properties :
35
30
High Proton conductivity
up to 34.5 mS/cm
25
20
15
10
At 30 °C and
100% RH
5
0
0.8
1.0
1.2
1.4
1.6
1.8
2.0
IEC (meq/g)
Proton conductivity of SPIs as a function of IEC
Limitation: Suffers with poor hydrolytic stability
O
The major concern of the
synthesized sulfonated polyimide
membranes is that they suffer from
hydrolytic degradation in acidic
medium during acid treatment and
subsequently all the membrane
becomes brittle after a certain
time.
N
O
HO3S
+H
HO3S
+ H2O
N
SO3H
OH2
HO
OH
HO3S
N
SO3H
O
SO3H
O
-H / +H
O
C OH
C NH
OH
HO3S
NH
HO3S
-H / +H
SO3H
OH
HO
OH
C OH
HO3S
C NH
O
SO3H
O
SO3H
+ H2 O
O
C OH
C NH
H2O
OH
-H / +H
HO
H2N
H2
N
C
SO3H
HO3S
O
C OH
HO3S
OH
HO3S
SO3H
SO3H
-H
+
O
C OH
Mechanism of hydrolytic degradation
Imide
Acid- amide
Carboxylic diacid
DQB90 (1N HCl treated)
DQB80 (1N HCl treated)
Acid-hydrolysis of 5-membered imide ring leads to
chain scission and subsequently,
DQB70 (1N HCl treated)
DQB60 (1N HCl treated)

Membrane becomes brittle

Mw of the polymer decreases
DQB50 (1N HCl treated)
C OH
O
Studies on semifluorinated 6-Membered SPIs
O
O
N
N
O
O
O
CF3
O
O
O
N
N
O
O
1-m
F3C
DQN XX series
HO3S
SO3H
m=0.4, DQN 40
=0.5, DQN 50
=0.6, DQN 60
=0.7, DQN 70
=0.8, DQN 80
=0.9, DQN 90
• Possess good solubility in common organic solvents
• High molecular weight
• Excellent thermal and mechanical properties
• Good dimensional stability with decent hydrolytic-oxidative stability
• Nano-scale phase separated structure
• High proton conductivity.
m
Physical Properties
Thermal
Mechanical
100
100
Weight (%)
80
1
2
3
4
5
6
60
40
DQN40
DQN50
DQN60
DQN70
DQN80
DQN90
Tensile Stress (MPa)
Dry Membranes
1
6
54
2
3
20
heating rate: 10 °C min-1 ; in air)
0
100
200
300
400
1
3
80
4
5
60
40
Excellent mechanical properties
(tensile strength ranging from
65.4–105.6 MPa and Young’s
moduli of 1.56–2.0 Gpa)
20
0
2
1
2
3
4
5
DQN40
DQN50
DQN60
DQN70
DQN80
0
500
600
0
700
10
20
30
40
50
Tensile Strain (%)
Temperature (oC)
Stress-strain plot of DQN membranes
TGA thermograms of the DQN polymers;
Chemical stability
Polymer
membrane
DQN40
Hydrolytic
stability a
(h)
>250
Oxidative
stability b (h)
τ1
τ2
3.8
>24
DQN50
>250
3.5
>24
DQN60
>250
3
20
DQN70
>250
1.2
9
DQN80
~120
0.8
4.5
a
Time that the membrane is completely dissolved in deionized
water at 80 °C.
b Tests performed in Fenton’s reagent at 80 °C. τ and τ are the
1
2
elapsed times in which the membranes start to break and
dissolve completely..
Microstructure IEC and proton conductivity
•
Excellent nano phase
separated structure
•
High proton conductivity in
the range of Nafion at 100
% relative humidity
16000
DQN40
DQN50
DQN60
DQN70
DQN80
DQN90
14000
DQN 80
12000
Z" (Ohm)
DQN 70
DQN 60
DQN 50
TEM micrographs of SPI membranes (cross section, Ag+ form)
•
10000
8000
6000
4000
PEM properties:
2000
0
Arrhenius equations, σ = Ae-Ea/RT
5000 10000 15000 20000 25000 30000 35000
Z' (Ohm)
90
5.0
80
DQN40
DQN50
DQN60
DQN70
DQN80
DQN90
4.5
70
O
4.0
-1
)
at 30 C
60
50
ln s (mS. cm
Proton Conductivity (mS/cm)
0
40
30
20
10
Variation in the impedance behaviour
Polymer
membrane
IEC
(meq/g)
3.5
Proton
conductivity
(mS cm-1)
30 °C 80°C
Ea
(kJ/mol)
theo.a
exp.b
DQN40
1.03
0.98
5
9.4
11
DQN50
1.34
1.36
6.5
13.2
12.2
DQN60
1.67
1.67
7.6
17
14.6
DQN70
2.03
n.d.
22.8
39.6
8.9
DQN80
2.42
n.d.
54.5
80.6
7.2
DQN90
2.85
n.d.
81.9
108.2
4.6
3.0
2.5
2.0
0
1.0
IEC
1.5
theo
2.0
(mm
ol/g)
2.5
3.0 10
15
20
W
25
r
at e
30
Up
35
t
40
45
(w
ake
Correlation plot of IECtheo, WU and proton
conductivity
)
t. %
1.5
2.8
2.9
3.0
3.1
3.2
3.3
3.4
-1
1000/T (K )
Temperature dependence of proton
conductivity
Studies on semifluorinated sulfonated poly(arylene ether sulfone)s
Reaction scheme:
n Cl
NaO3S
O
S
O
SDCDPS
SO3Na
Cl
CF3
CH3
+
OH + (1-n) F
HO
CH3
BPA
F
F3C
QBF
K2CO3
NMP
180 oC
O
S
O
SO3Na
CF3
CH3
O
O
CH3
NaO3S
n
F3C
HO3S
SO3H
BPAQS-xx
O
CH3
hydrophilic
CF3
CH3
O
O
CH3
H+
O
S
O
CH3
O
n
XX
0.2
0.3
0.4
0.5
0.6
20
30
40
50
60
CH3
O
n
F3C
(1-n)
O
CH3
(1-n)
hydrophobic
BPAQSH-xx
Approach to the structural designing:
•QBF is incorporated to control the DS of the random copolymer BPAQSH-xx
•-CF3 group in QBF increases the hydrophobicity of non-sulfonated backbone
segment over sulfonated segment which may help for good phase separated
morphology
•SDCDPS with features of localized sulfonic acid density and rigid QBF moiety are incorporated into the backbone
structure of polymer to increase the statistical length of non-sulfonated segment which may help to obtain good
mechanical property, high hot water stability and high proton conductivity.
•rigid structure with pendant -CF3 group of QBF moiety will help to attain good
solubility, thermal, oxidative stability
Thermal properties, mechanical properties and
oxidative stability
Polymer
Tga
(/oC)
Td5%
b
Td1 b
(/oC)
Td2 b
(/oC)
TS
(/Mpa)
Y
(/GPa)
EB
(/%)
Oxidative stability,
tc (/h)
(/oC)
BPAQ
216
476
431
-
40
1.04
59
-
BPAQSH-20
245
365
393
546
57
1.55
18
29.6
BPAQSH-30
257
355
389
533
49
1.25
21
25.8
BPAQSH-40
ND
347
368
528
37
1.05
19
4.5
BPAQSH-50
ND
310
366
526
35
1.02
18
4.3
BPAQSH-60
ND
283
261
512
27
0.91
4
3.8
a
glass transition temperature determined by DSC, heating rate 10 oC/min under nitrogen.
b
td refers to decomposition temperature measured by TGA, heating rate 10 oC/min under air.
c
‘t’ refers to the time expended for the membrane beginning to break in
Fenton’s reagent (2ppm FeSO4 in 3% H2O2) at 80 oC.
Microstructure and PEM properties
BPAQS-30
BPAQS-40
BPAQS-50
TEM micrograph of lead-stained BPAQS-XX copolymers
BPAQS-60
PEM properties:
Polymer
ηinha
(dL/g)
IECW
(meq/g)
WUW (%)
σ (mS/cm)
Swelling
(%)
Titr.
30 oC
80 oC
30 oC
80 oC
30 oC
80 oC
Eab
(KJ/mol)
xx=20
1.28
0.58
4
7
2.2
2.6
9
25
17.26
xx=30
1.25
0.84
7
12
2.8
3.3
13
31
16.44
xx=40
1.23
1.18
12
18
4.0
5.3
16
40
15.72
xx=50
1.21
1.46
22
36
4.6
6.3
31
71
13.96
xx=60
1.19
1.70
40
52
6.2
10.2
40
80
11.34
a inherent
viscosity of BPAQS-XX copolymers in NMP at 30 °C;
energy determined in the temperature range: 30-90 oC and heating rate 1-2 oC/min.
b activation
PEM properties
100
for BPAQSH-XX copolymers
o
80 C
50
40
o
30 C
30
20
10
0.6
0.8
1.0
1.2
1.4
1.6
1.8
for BPAQSH-XX copolymers
80
60
40
Inflection point
20
0
0.4
0
2.0
o
at 30 C
o
at 80 C
0.6
5.0
σ = Ae-Ea/RT
1.0
1.2
1.4
1.6
1.8
Proton conductivity as a function of IEC
Water uptake as a function of IEC
Arrhenius equation:
0.8
IECw (meq/g)
IECw (meq/g)
(I)BPAQSH-20
(II)BPAQSH-30
(III)BPAQSH-40
(IV)BPAQSH-50
(V)BPAQSH-60
4.5
4.0
V
Ln(smS/cm)
Water uptake (wt. %)
60
Proton conductivity, s (mS/cm)
70
3.5
IV
3.0
Arrhenius temperature dependence of
proton conductivity (σ) of BPAQSH-XX
membranes
III
II
2.5
I
2.0
2.7
2.8
2.9
3.0
3.1
1000K-1/T
3.2
3.3
3.4
Summary
 Both the synthesized aromatic SPIs and poly(arylene ether sulfone)s draw special attention as high
performance polymeric materials with ease of processability and possessing an excellent balance
between thermal , mechanical properties and proton conductivity.
 The synthesized 5-membered SPI (DQB XX) membranes are hydrolytically unstable and all the
membranes undergoes hydrolysis upon long treatment with acid solution or long term keeping in water
at room temperature but the 6-membered SPI (DQN XX) possess excellent hydrolytic-oxidative
stability.
 Introduction of ether linkages (―O―) and bulky (―CF3) pendent group into polymer chain resulted in
increase in many physical properties like solubility, processability, dimensional stability and chemical
stability.
 Hydrophobic (―CF3) group also helps to form well phase separated structure responsible for better
proton conductivity.
 High proton conductivity have been achieved for the membranes having moderately high IEC
(88mS/cm at 90 oC for BPAQSH-60 and 108.2 mS/cm at 80 oC for DQN-90 sample).
 Overall combination of good PEM properties renders BPAQSH-50, BPAQSH-60 and DQN-70, DQN-80
as potential candidate for use as PEM materials.
306