SCH4U Synthesis and
Polymers
Synthesis Reactions and
Addition and Condensation Polymers
ADDITION POLYMERS
ADDITION POLYMERS
A + A + A + A
A
monomers
+
+
+
A
A
polymer
+
ethylene (ethene)
+
A
polyethylene
linear
+
propylene (propene)
many (n)
monomers
polypropylene
nA
(A) n
polymer
branched
POLYMERISATION OF ALKENES
ADDITION POLYMERISATION
Process: alkene adds to itself
• all the atoms in the original alkenes are used to form the polymer
• long hydrocarbon chains are formed
equation shows the original monomer and the repeating unit in the polymer
n
represents a
large number
ethene
poly(ethene)
MONOMER
POLYMER
POLYMERISATION OF ALKENES
EXAMPLES OF ADDITION POLYMERISATION
ETHENE
PROPENE
CHLOROETHENE
VINYLCHLORIDE
TETRAFLUOROETHENE
POLY(ETHENE)
POLY(PROPENE)
POLY(CHLOROETHENE)
POLYVINYLCHLORIDE
PVC
POLY(TETRAFLUOROETHENE)
PTFE
“Teflon”
POLYMERISATION OF ALKENES
SPOTTING THE MONOMER
“Styrofoam”
styrene
Catalyst
+
could be as simple
as a proton from
sulfuric acid
Catalyst
+
H 2 SO 4 or
(+)
cationic
catalyst
R
resonance
stabilized
(+)
(Markovnikoff)
(+)
R
+
+
etc.
Polystyrene
POLYSTYRENE
R
n
repeating
unit
COPOLYMERS
Polymers which are formed by combining two different
monomers in alternating fashion are called copolymers.
A + B + A + B
A
B
A
B
butadiene
styrene
styrene -butadiene
rubber (SBR)
THERMOPLASTICS
Thermoplastics can be softened or melted by heat
and reformed (molded) into another shape.
Most addition polymers are thermoplastics.
The polymer chains are held together by weak
interactions (noncovalent bonds) such as :
van der Waal's forces,
London dispersion forces and
Dipole -dipole attractions.
These interactions are disrupted by heating, allowing
the chains to become independent of each other.
Heating and reforming can be repeated indefinitely
(if degradation doesn't occur). This allows recycling.
PLASTICIZERS
Most polymers of high molecular weight are quite rigid.
Can be softened and made flexible by adding plasticizers
O
C
C
O
O CH 2 CH 2 CH 2 CH 3
O CH 2 CH 2 CH 2 CH 3
dibutyl phthalate
The plasticizer separates the individual polymer chains
from one another. It acts as a lubricant which reduces
the attractions between the polymer chains.
THERMOSET PLASTICS
Thermoset plastics melt initially, but on further
heating they become permanently hardened.
Once formed, thermoset plastics cannot be
remolded, and they cannot be recycled.
On heating, thermoset plastics become cross -linked
(covalent bonds form between the chains). The
cross-linked chains form a rigid network
heat
linear
cross-linked
HIGH -DENSITY POLYMERS
Linear polymers with chains that can pack closely
together. These polymers are often quite rigid.
LOW-DENSITY POLYMERS
Branched -chain polymers that cannot pack together
as closely. There is often a degree of cross -linking.
These polymers are often more flexible than high density polymers.
SOME COMMON ADDITION POLYMERS
example
monomer
polymer
polyethylene
CH 2
CH 2
polypropylene
CH 2 CH
CH 2
CH 3
polystyrene
CH 2 CH
polyvinyl chloride CH 2 CH
(PVC)
Cl
CH 2
CH 2 CH
CH 3
CH 2 CH
uses
most common polymer
bags, wire insulation,
squeeze bottles
fibers, bottles,
indoor-outdoor carpet
styrofoam,
inexpensive molded
objects: household items,
toys
synthetic leather, clear
bottles, floor coverings,
water pipe
CH 2 CH
Cl
Teflon
CF 2 CF 2
CF2 CF2
non-stick surfaces,
chemically resistant items
polyacrylonitrile
CH 2 CH
CH 2 CH
fiber used in sweaters,
blankets, carpets
(Orlon, Acrilan)
C N
C
N
COMMON ADDITION POLYMERS (cont)
example
poly(methyl
methacrylate)
monomer
polymer
CH 3
CH 3
CH 2
C
(Lucite, Plexiglass)
poly(vinyl acetate)
CH 2
(PVA)
CH
O C CH 3
O
O
CH 3
CH 2
C CH CH 2
CH 3
CH 2 C
neoprene rubber
adhesives,
latex paints,
textile coatings
chewing gum
CH 2 CH
O C CH 3
natural rubber
unbreakable glass,
latex paint
CO 2 CH 3
CO 2 CH 3
CH 2
C
uses
CH CH 2
the polymer is crosslinked with sulfur
(vulcanization)
Cl
CH 2
C
CH
CH 2
Cl
CH 2 C
CH CH 2
cross-linked with ZnO,
resistant to gasoline
and oil
Polymers and Polymerization
RECYCLING CODES
CODE SYSTEM FOR PLASTIC MATERIALS
These codes allow consumers to separate plastics for recycling.
1
2
3
4
PETE
polyethylene
terephthalate
soft drink bottles
HDPE
high-density
polyethylene
milk and beverage
containers, products
in squeeze bottles
V
polyvinyl
chloride
bottles with cleaning
agents in them, some
shampoo bottles
LDPE
low-density
polyethylene
thin plastic bags,
plastic wrap
PLASTIC MATERIALS CODE SYSTEM (cont)
5
PP
polypropylene
heavy-duty,
microwavable containers
used in the kitchen
6
PS
polystyrene
foam beverage cups,
envelope windows
7
Other
All other resins,
multilayered materials,
containers made of
other materials
ketchup bottles,
snack containers,
mixtures where
the top differs from
the bottom
The codes are frequently stamped on the bottom of containers.
CONDENSATION POLYMERS
A DIFFERENT TYPE OF POLYMER
NOT AN ADDITION POLYMER !
CONDENSATION POLYMERS
Condensation polymers are copolymers made from
more than one type of monomer.
Many functional groups are used (instead of alkenes)
and each type of monomer has a different functional
group.
When condensation polymers are formed, a small
molecule (usually H 2 O) is often eliminated as each
bond forms.
HO
Ethylene glycol
O
O
C
C OH
Terephthalic acid
H
O
CH 2CH 2
O
O
C
C
OH
O CH 2CH 2
Dacron polymer
O
+ H 2O
SOME COMMON CONDENSATION POLYMERS
CONDENSATION POLYMERS
Examples
Synthesis
polyamides
polyesters
peptides
starch
(nylon)
(terylene)
reactions between Dicarboxylic acids and diols
Dicarboxylic acids and diamines
Amino acids
ESTER LINK
AMIDE LINK
POLYAMIDES - NYLON -6,6
Reagents
Equation
hexanedioic acid
hexane-1,6-diamine
HOOC(CH2 )4 COOH
H2 N(CH2 )6 NH2
n HOOC(CH2)4COOH + n H2N(CH2)6NH2 ——> -[NH(CH2)6NHOC(CH2)4CO] n- + n H2O
Product
Nylon-6,6
two repeating units, each with 6 carbon atoms
Repeating unit
—[-NH(CH2 )6 NHOC(CH2 )4 CO-]n —
Properties
contain a peptide (or amide) link
can be broken down by hydrolysis
the C-N bond breaks
behave as amides
biodegradable
can be spun into fibres for strength
Uses
fibres and ropes
PEPTIDES
Amino acids join together via an amide or peptide link
a dipeptide
2 amino acids joined
3 amino acids joined
many amino acids joined
dipeptide
tripeptide
polypeptide
PROTEINS
• polypeptides with large relative molecular masses (>10000)
• chains can be lined up with each other
• the C=O and N-H bonds are polar due to a difference in electronegativity
• hydrogen bonding exists between chains
dotted lines ---------- represent hydrogen bonding
Interpeptide interactions, especially
hydrogen bonds, lead to complex
structures and folding patterns.