refers to the use of external
techniques to probe into the internal
structure and properties of a
material.
GEL PERMEATION CHROMATOGRAPHY
DIFFERENTIAL SCANNING CALORIMETRY
THERMOGRAVEMETRIC ANALYSIS
INFRA RED SPECTROSCOPY
POROSITY
TECHNIQUES FOR PROSITY ANALYSIS
Mikhail Tswett, Russian, 1872-1919
Botanist
In 1906 Tswett used to chromatography to
separate plant pigments
He
called
the
new
technique
chromatography because the result of the
analysis was 'written in color' along the
length of the adsorbent column
Chroma means “color” and graphin means to “write”
…is a technique used to separate and identify the
components of a mixture.
Works by allowing the molecules present in the mixture to distribute
themselves between a stationary and a mobile medium.
Mobile phase
Mobile phase is a liquid as water
or dilute alcohol
Separation mechanism
Based on difference between the
solutes molecular weights.
Molecules will distribute themselves outside & inside
the pores according to their size.
This type is also known as:
GPC can determine several important parameters. These include number average
molecular weight, weight average molecular weight, and the most fundamental
characteristic of a polymer its molecular weight distribution.
These values are important, since they affect many of the characteristic physical
properties of a polymer.
Tensile strength
Elastomer relaxation time
Brittleness
Impact strength
Toughness
Adhesive strength
Cure time
Elastic modulus
Hardness
Softening temperature
"Size Exclusion" chromatography
Molecular weight distribution
Polymer solution
small molecules
Column
medium molecules
Large molecules
Number average Molecular weight
Separation based on Size
Weight average Molecular weight
Size exclusion chromatography
Large particles cannot enter gel and are
excluded. They have less volume to
traverse and elute
Small particles can enter gel and have
more volume to traverse. They elute later
chromatogram
flow
time
How GPC works
SEC was first developed in 1955 by Lathe and Ruthven
GPC separates molecules in solution by their "effective size in solution." To
prepare a sample for GPC analysis the polymer sample is first dissolved in an
appropriate solvent.
Inside the gel permeation chromatograph, the dissolved sample is injected into a
continually flowing stream of solvent (mobile phase). The mobile phase flows
through millions of highly porous, rigid particles (stationary phase) tightly
packed together in a column.
The pore sizes of these particles are controlled and available in a range of sizes.
Schematic of a basic Gel permeation chromatograph
sample
Data
system
Solvent
delivery
system
Solvent
supply
Mobile phase
injector
Column(s)
detector(s)
Small molecules
penetrate pores
of particles
Large molecules
are excluded
Polymer – Dissolving in solvent
Membranes – Passed through std. sol.
MWCO (Molecular weight Cut-Off)
High temperature GPC
Basic Principles of Thermal Analysis
Modern instrumentation used for thermal analysis usually consists of the
following parts:
sample holder/compartment for the sample
sensors to detect/measure a property of the sample
and the temperature
an enclosure within which the experimental parameters
(temperature, speed, environment) may be controlled
a computer to control data collection and processing
Temperature
Control (Furnace)
sample
Sensors
PC
Differential
two calorimeters (for sample and reference) with the same
heat transfer behavior (for compensation purpose)
Scanning
the common operation mode is to run temperature or
time scans
Calorimeter
instrument to measure heat or heat flow
Amorphous Phase
Crystalline Phase
Semi-crystalline Polymers
Melting
The portion of material whose molecules are randomly oriented in
space. Liquids and glassy or rubbery solids. Thermosets and some
thermoplastics.
The portion of material whose molecules are regularly arranged into
well defined structures consisting of repeat units. Very few polymers
are 100% crystalline.
Polymers whose solid phases are partially amorphous and partially
crystalline. Most common thermoplastics are semi-crystalline.
The endothermic transition upon heating from a crystalline solid to
the liquid state. This process is also called fusion. The melt is
another term for the polymer liquid phase.
Semi-Crystalline (or Amorphous)
Crystalline Phase
melting temperature Tm
(endothermic peak)
Amorphous Phase
glass transition temperature (Tg)
T g < Tm
Crystallisable polymer can crystallize
on cooling from the melt at Tc
(Tg < Tc < Tm)
Gas control
Furnace
differential detector
temperature controller
signal amplifier
furnace
Sample
Reference
Temperature
controller
Detectors
gas control device
data acquisition device
Microvolt
amplifier
Data
acquisition
Sample Pan
Pan sealed
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.
Heat Flow - > exothermic
Typical DSC Curve of a Thermosetting Polymer
Cross -Linking
(Cure)
Crystallization
Glass
Transition
Melting
Temperature
Oxidation
Typical Features of a DSC Trace
Exothermic upwards
Endothermic downwards
Melting (Tm)
(Tc)
Glass Transition (TCrystallization
g)
Desolvation
H 2O
Decomposition
Y-axis – heat flow
X-axis – temperature (and time)
Temperature (oC)
DSC Curve : Heat/Cool/Heat
1.5
cooling
Heat Flow (W/g)
1.0
0.5
first heating
0.0
-0.5
second heating
-1.0
-1.5
0
40
80
120
Temperature (°C)
160
200
240
Onset = Melting point (mp)
^exo
20
mW
Heat of fusion (melting) =
integration of peak
40
60
80
100 120 140 160 180 200 220 240 260 280 300
o
temperature(o[C)
C]
Temperature
Influence of Sample Mass
DSC Heat Flow (W/g)
0
Indium at
10°C/minute
Normalized Data
-2
15mg
Onset not
influenced
by mass
10mg
4.0mg
-4
1.7mg
1.0mg
0.6mg
-6
150
152
154
156
158
160
Temperature (°C)
162
164
166
A technique measuring the variation in mass of
a sample undergoing temperature scanning in a
controlled atmosphere
Thermobalance allows for monitoring sample
weight as a function of temperature
The sample hangs from the balance inside the
furnace and the balance is thermally isolated
from the furnace
Gas IN
Sample: RCD 1
Size: 4.9250 mg
Method: Ramp
TGA
File: D:\TGA-DSC\TGA\NafionRCD_1.008
Operator: LK
Run Date: 10-Sep-2012 17:52
Instrument: TGA Q500 V20.13 Build 39
120
100
Weight (%)
80
60
40
20
0
0
200
400
Temperature (°C)
600
800
Universal V4.5A TA Instruments
TGA in Nitrogen and Oxygen atmosphere
%
%
100
Nitrogen
IDT
80
Weight Loss
Weight Loss
80
Oxygen
60
40
Poly(PMDA-ODA-IPC)
20
200
300
Poly(PMDA-ODA-IPC
Poly(PMDA-ODA-TPC)
Poly(PMDA-ODA-TMAc)
100
40
20
Poly(PMDA-ODA-TPC)
0
60
400
500
Temperature
600
700
800 °C
CD
Poly(PMDA-ODA-TMAc)
0
100
200
300
400
500
Temperature
Data :
IDT - Initial decomposition Temp
Weight Vs Time
CD - Complete decomposition
Weight Vs Temperature
600
700
800 °C
Weight Loss (%)
Step-I
Step-II
Step-III
Temperature (oC)
The entire electromagnetic spectrum is used by chemists:
~1019
~1017
~1015
~1013
~1010
~105
~.0001 nm
~0.01 nm
10 nm
1000 nm
0.01 cm
100 m
~10-4
~10-6
> 300
g-rays
X-rays
nuclear
core
excitation (PET) electron
excitation
(X-ray
cryst.)
300-30
300-30
UV
electronic
excitation
(p to p*)
IR
molecular
vibration
Visible
Microwave
molecular
rotation
Radio
Nuclear Magnetic
Resonance NMR
A molecule such as H2O will absorb infrared light when the vibration (stretch
or bend) results in a molecular dipole moment change
Symmetric Stretch
Asymmetric Stretch
Bend
A molecule can be characterized (identified) by its molecular vibrations, based on the
absorption and intensity of specific infrared wavelengths.
Water
O-H Bend
O-H Stretching
The Infrared region is divided into: near,
mid and far-infrared.
–
Near-infrared refers to the part
of the infrared spectrum that is
closest to visible light and farinfrared refers to the part that
is closer to the microwave
region.
–
Mid-infrared is the region
between these two
The four primary regions of the IR spectrum
Bonds to H
Triple bonds
OH single bond
NH single bond
CH single bond
Single Bonds
Double bonds
CC
CN
CO
C=O
C=N
C=C
C≡C
C≡N
Fingerprint
Region
4000 cm-1
2700 cm-1
2000 cm-1
1600 cm-1
400 cm-1
Non-porous solid
Low specific surface area
Low specific pore volume
Porous solid
High specific surface area
High specific pore volume
Porous materials have highly developed internal surface area that can be
used to perform specific function. Almost all solids are porous except for
ceramics fired at extremely high temperatures
Inter-connected
(open)
closed
Open pores are accessible whereas
closed pores are inaccessible pores.
Open pores can be inter-connected,
passing or dead end.
Passing (open)
Dead end
(open)
Size of Pores (IUPAC Standard)
Macropores
Mesopores
Micropores
Zeolite,
Activated
carbon,
Metal organic
framework
Mesoporous silica,
Activated carbon
2 nm
Sintered metals
and ceramics
50 nm
Porous material are classified according to the size of pores: material with pores less
than 2 nm are called micropores, materials with pores between 2 and 50 nm are
called mesopores, and material with pores greater than 50 nm are macrospores
Gas
adsorption
Gas
adsorption
Small angle
Neutron
scattering
Mercury
Porosimetry
Techniques
Small angle
X-ray
scattering
TEM
SEM
Typical Pore Structure
Conclusion
Gel permeation chromatography (GPC) is a type of
chromatography (SEC), that separates analytes on the basis of size.
size exclusion
DSC is a thermoanalytical technique in which the difference in the amount of heat
required to increase the temperature of a sample and reference is measured as a
function of temperature
TGA is a type of testing performed on samples that determines changes in weight in
relation to a temperature program in a controlled atmosphere.
IR spectroscopy used to identify and study chemical structure of material in the
Infra red region
Porous material : micropores, mesopores and macropores