Lesson 3: Characterization, Analysis, Testing Flashcards
is the analytical branch of polymer science.
Polymer characterization
is a technique used to determine the molecular properties, structure, and behavior of polymers.
Polymer characterization
➢Characterization techniques are typically used to determine
molecular mass, molecular structure, morphology,
thermal properties, and mechanical properties.
The ____ of a polymer differs from typical molecules, in
that polymerization reactions produce a distribution of molecular
weights and shapes.
molecular mass
The distribution of molecular masses can be summarized by the
number average molecular weight, weight average molecular weight,
and polydispersity.
➢There are four molecular weight
averages in common use:
number-average molecular
weight, Mn; the weight-average
molecular weight, Mw; the z-average molecular weight, Mz; and the viscosity-average molecular weight, Mv
If all species in a polymer sample have the same molecular weight, the polymer is
monodisperse
➢The ratio Mw/Mn is called the ____ is commonly used as a simple measure of the polydispersity of the polymer sample.
polydispersity index (PDI)
➢The molecular weight of polymers can be determined by a
number of physical and chemical methods.
- end group analysis
- measurement of colligative properties
- light scattering
- Ultracentrifugation
- dilute solution viscosity
- gel permeation chromatography (GPC).
➢The ____ is a chemical method use for calculating the number-average molecular weight of polymer samples whose molecules contain reactive functional groups at one end or both ends of the molecule.
end-group analysis
➢This method is limited to the determination of polymers with a molecular weight of less than about 20,000.
End-group Analysis
Method of _____ analysis
✓Titrimetric method
✓Nuclear magnetic resonance (NMR)
✓mass spectrometry
✓vibrational spectrometry, like infrared and raman spectroscopy.
End grp analysis
➢End-group analysis is not applicable to
polymers that lack reactive or easily detectable end-groups.
high molecular weights
➢Properties of solutions that depend on the number of molecules present and not on the kind of molecules are called
colligative properties
colligative properties include
boiling point elevation, freezing point depression, and osmotic pressure.
Boiling Point Elevation or
Ebulliometry
In applying this method, the boiling point of a solution of known concentration is compared to that of the solvent at the same pressure
Boiling Point Elevation
✓Boiling point of the solution is ____ than the pure solvent. This phenomenon is used to determine the molecular weight of polymers
higher
_____, like end-group analysis, is
limited to low-molecular-weight polymers.
Ebulliometry
It works by analyzing the melting behavior of a substance as it is frozen. By measuring the time it takes for a specific substance to melt at a certain temperature, its molecular weight can be calculated.
Cryoscopy (Freezing Point Depression)
Like ebulliometry, the cryoscopic method is also limited to relatively low-molecular-weight polymers
with Mn up to ___.
50,000
____ is the most important among all colligative properties for the determination of molecular weights of synthetic polymers.
Osmotic pressure
____ is a technique for the determination of molecular masses of polymers by means of osmosis. The phenomenon of osmosis describes the attempt of solvent molecules to go through a ___ into a solution.
Membrane osmometry, semipermeable membrane
Membrane osmometry is useful to determine Mn about ____ and less than _____
20,000-30,000 g/mol, 500,000 g/mol
The main drawbacks to ____ are that it is time consuming and sensitive to changes in the
atmospheric pressure.
ebulliometry
It is not suitable for use with volatile substances or highly reactive chemicals due to the risk of explosion.
Ebulliometry
One disadvantage for ___ is that the process can be time-consuming, as it requires a sudden freezing and slow thawing process.
cryoscopy
Another disadvantage of this process can be sensitive to impurities in the monomer solutions, which can lead to
defective polymer formation
Cryoscopy
_____ is simple but takes several hours to few days in diffusion of solvent through the semipermeable membrane. It is a very slow process and the time taken to attain equilibrium is extremely
high.
Membrane osmometry
Membrane osmometry is useful in themolecular weight range of
30,000 to 1,000,00
The measurement of ___ by polymer solutions is an important technique for the determination of weight-
average molecular weight, Mw. It is an absolute method of molecular weight measurement.
light scattering
___ is a technique that measures the intensity of the scattered light to obtain the average molecular weight Mw of a macromolecule like a polymer or a
protein in solution.
Static light scattering
In a ___ measurement, a coherent laser beam is used to analyze a sample.
static light scattering
One of the great advantages of ___ is that it provides information about macromolecules without any calibration with polymer.
standards.
light scattering
The drawback is that it is non-selective and thus requires
purified extracts without co-eluting contaminants in order to generate
useful data.
Light scattering
✓Requires a solvent with a different refractive index compared to the solute (usually this is fine for most biomacromoleculesin aqueous buffers).
Light-Scattering Method
➢___ is defined as the measure of the opposing force of material to
flow.
Viscosity
➢____ gives the relationship between viscosity and
average molecular weight:
Mark-Houwink equation
➢ It is the most common type of
viscometer that is used for the
determination of viscosity of polymer solution.
Ubbelohde viscometer
✓One disadvantage is that viscometry is generally limited to measuring materials in the ___ state
liquid or semi-liquid
Higher concentration
leads to a ___ viscosity measurement.
higher
➢ ____ is an extremely powerful method for determining the
complete molecular weight distribution and average molecular weights.
Gel permeation chromatography (GPC)
It is essentially a process for the separation of polymer molecules according to their size.
Gel permeation chromatography (GPC)
GPC is also known as
gel filtration, gel exclusion chromatography, size-exclusion chromatography (SEC), and molecular sieve chromatography.
mitations/Disadvantages
✓ There is a limited number of peaks that can be resolved within the short time scale of the GPC run. GPC requires around at least a __ difference in molecular weight for a reasonable resolution of peaks to occur.
10%
➢___ are used to purify and characterize low-molecular-weight polymers.
Ultracentrifuges
➢The ___ is operated at extremely high speeds up to ___ rpm in order to transport the denser polymer molecules through the less dense solvent to the cell bottom
ultracentrifuge, 70,000
Limitations of Ultracentrifugation
Low sample yield
Time consuming
extremely expensive devices
➢The two techniques that are encountered most commonly are
intrinsic viscosity and GPC.
➢___ has proved to be a rapid and precise method of molecular-weight
determination, often requiring as little as a half hour per sample.
GPC
Many of the analytical techniques used to determine the ___ of unknown organic compounds are also used in polymer characterization.
molecular structure
➢__ is a microscale property that is
largely dictated by the amorphous or crystalline portions of the polymer chains and their influence on each other.
Polymer morphology
➢Some of the most common microscopy techniques used
are
X-ray diffraction, Transmission Electron Microscopy,
Scanning Transmission Electron Microscopy, Scanning
Electron Microscopy, and Atomic Force Microscopy.
ANALYSIS AND TESTING
A. CHEMICAL ANALYSIS OF POLYMERS
B. SPECTROSCOPIC METHODS
C. X-RAY DIFFRACTION ANALYSIS
D. MICROSCOPY
E. THERMAL ANALYSIS
F. PHYSICAL TESTING
➢Both ____ may be determined by subjecting dilute solutions of polymers in appropriate solvents to ultracentrifugal forces at high speeds. Solvents with densities and indices of refraction ____ from the polymers are chosen to ensure polymer motion and
optical detection of this motion.
Mw and Mz; different
➢In the most common applications of _____ to polymer systems, the polymer is allowed to react to form ____ that are condensed at liquid-air temperature
mass spectrometry; low-molecular-weight fragments
In mass spectrometry, ___ is an ionization technique that uses a laser energy-absorbing matrix to create ions from large molecules with minimal fragmentation.
matrix-assisted laser desorption/ionization (MALDI)
In polymer chemistry, MALDI can be used to determine the
molar mass distribution
Mass Spectrometry Strengths:
1.Compound Identification
2.High Sensitivity and Specificity
3.Quantitative Analysis
Limitations of mass spec
1.Sample Preparation: Samples need to be compatible with the ionization method and may require extensive preparation steps.
2.Complexity and Cost: Mass spectrometers can be expensive to
purchase, maintain, and operate.
3.Instrument Sensitivity: Sensitivity can be affected by the presence of contaminants or interfering compounds.
____ is a method of separation in
which gaseous or vaporized components are distributed between a moving gas phase and fixed liquid phase or solid adsorbent.
Gas Chromatography
___ is an analytical method that combines the features of gas-chromatography and mass spectrometry to identify different substances within a test sample.
Gas chromatography–mass spectrometry (GC–MS)
It is an analytical technique used to separate the chemical components of a sample mixture and then
detect them to determine their presence or absence. It is also used to figure out how much is present in the sample.
Gas chromatography
can provide detailed information about the molecular structure and composition of polymers, including their monomer sites, stereochemistry, and branching patterns.
GC-MS
Gas Chromatography Strengths
High Separation Efficiency: Allows the separation of complex mixtures into individual components, even for compounds present in trace amounts.
Quantitative Analysis: Provides accurate quantification of compounds through calibration curves or peak area integration in the chromatogram.
Wide Range of Applications: Applicable to a diverse range of sample types and compounds, offering versatility in analytical tasks
Limitations of GC
Limited Volatility: Compounds need to be volatile or semi-volatile to be efficiently separated and
detected by GC.
Thermal Stability: Some compounds may decompose or react within the high-temperature
environment of the GC column, affecting their separation and detection.
Sample Preparation: Sample preparation steps, such asextraction and derivatization, might be required, adding complexity to the analysis.
SPECTROSCOPIC
METHODS
- Infrared Spectroscopy
- Nuclear Magnetic Resonance
(NMR) spectroscopy - Electron Paramagnetic Resonance Spectroscopy
- Ultraviolet-visible spectroscopy
- Raman spectroscopy
____ is the analysis of infrared light interacting with a
molecule.
Infrared Spectroscopy
Infared spec can be analyzed in
three ways by measuring _____.
absorption, emission and reflection
IR Spectroscopy measures the
___, and based on this it is possible to determine the ____.
vibrations of atoms, functional groups
___ is a non-destructive analytical technique that measures the absorption or transmission of
infrared radiation by a sample as a function of _____
Fourier transform infrared spectroscopy (FTIR), frequency or wavelength
____ is a reliable and cost-effective analytical tool for identification of polymers and assessment
of the quality of plastic materials.
Fourier Transform-Infrared Spectroscopy (FTIR)
(FTIR) Strengths:
◦ The strengths of FTIR include its _____, and ability to provide a wealth of information about the chemical composition and structure of a sample.
◦ FTIR can detect ___ of compounds in complex mixtures and can provide quantitative data.
◦ FTIR is also a ___ and rapid technique that can analyze solid, liquid, and gas samples.
high sensitivity, specificity
very small amounts
relatively simple
Limitations of FTIR
inability to provide information about the three-dimensional
structure of a molecule and its sensitivity to interference from water and other atmospheric gases.
◦ FTIR is also prone to interference from sample preparation artifacts, such as impurities or
contaminants.
◦ FTIR is a relatively expensive technique
____ is the subjective sensation in
the brain resulting from the
perception of those aspects of the
appearance of objects that result
from the spectral composition of the light reaching the eye.
Color
___ depends largely on the spectral power distribution of a light source, the spectral reflectance of the
illuminated object, and the spectral
response curves of the eye.
Color
___ is defined as the state permitting perception of objects through or
beyond the specimen.
Transparency
__ of polymers refers to their degree of clarity or opacity, or how much
they allow light to pass through them.
Transparency
ELECTRICAL PROPERTIES
Resistivity
Dielectric Constant
Dielectric Strength
Arc Resistance
___ of polymers refers to the ability of a polymer material to resist the flow of electrical current.
Resistivity
A ____ is a measure of a material’s ability to store electric charge.
dielectric constant
The ___ of a material is a measure of its ability to sustain high-voltage
differences without current breakdown.
dielectric strength
__ is a measure of the electrical strength of a material as an insulator.
Dielectric strength
__ dielectric strengths are typically
desirable in capacitors
Higher
__ is the ability of the plastic material to resist the action of a high voltage electrical arc and resist the formation of a conducting path along its surface under a given time.
Arc resistance
CHEMICAL PROPERTIES
Resistance to Solvents
Vapor Permeability
Weathering
___, in which the specimen fails by breaking when exposed to
mechanical stress in the presence of an organic liquid of an aqueous
solution of a soap or other wetting agen
environmental stress cracking
__, in which a specimen fails by the development of a multitude of very small cracks in the presence of an organic liquid or its vapor, with or without the presence of mechanical stress.
crazing
__ refers to the ability of a polymer material to allow certain gases or vapors to pass through it.
Vapor permeability
__ is directly measured as the rate of transfer of vapor through unit thickness of the
polymer in film form, per unit area and pressure difference across the film.
Permeability
___ of polymers refers to the process of degradation of polymers, or large molecules, due to exposure to external factors such as sunlight, temperature, and chemicals.
Weathering
is a
powerful analytical technique used to study the molecular
structure, dynamics, and composition of organic and inorganic
compounds. It exploits the magnetic properties of certain
atomic nuclei within a magnetic field to provide detailed
information about the chemical environment of atoms in a
molecule.
Nuclear Magnetic Resonance (NMR) spectroscopy
The major use of __ lies in the detection of free radicals. These species are uniquely
characterized by their magnetic moment, arising from the presence of an unpaired electron.
EPR spectroscopy
Electron Paramagnetic Resonance
_ is a valuable technique for analyzing polymers, providing insights into their electronic structure, composition, and molecular interactions. When applied to polymers, ___ is used to study the absorption of ultraviolet and visible light by polymer molecules.
UV-Vis spectroscopy
__ is an analytical technique used to study molecular vibrations in materials by measuring the
scattering of light when it interacts with a sample. It provides information about molecular structure, chemical composition, and bonding within a sample based on the vibrational modes of its constituent molecules.
Raman Spectroscopy
____ is a nondestructive
technique that provides detailed information about the crystallographic structure, chemical composition, and physical properties of a material.
X-Ray diffraction analysis (XRD)
has become the go-to tool for
identifying the type and crystallinity of polymer materials.
X-Ray diffraction analysis (XRD)
D. MICROSCOPY
- Light microscopy
- Electron microscopy
Light microscopy
Polarized light microscopy
Phase-contrast Microscopy
➢A __ is a
category of microscopes
that uses visible light to
magnify and image small
samples.
light microscope
➢__ is
valuable for examining the
texture of solid opaque
polymers.
Light Microscopy
__ is a technique used to observe the orientation of molecules in a sample under a microscope. It is
often used with polymers to study their structure, as the orientation of the polymer chains can reveal information about their molecular organization.
Polarized light microscopy
is a type of
microscopy that uses interference patterns
produced by the incoherent light scattered by
specimens to create an image.
Phase-contrast microscopy
The ___ uses a beam of
electrons and their wave-like characteristics to
magnify an object’s image, unlike the optical
microscope that uses visible light to magnify
images.
electron microscope
___ is a powerful tool in the
study of the morphology of crystalline polymers.
Electron Microscopy
A __ is a
type of electron microscope that produces
images of a sample by scanning the surface
with a focused beam of electrons
scanning electron microscope (SEM)
contain
information about the surface topography
and composition of the sample.
SEM
is a
type of electron microscope that transmits
electrons through a thin sample, resulting in an
image of the sample’s interior structure at the
atomic level.
transmission electron microscope (TEM)
analytical technique used to visualize the
smallest structures in matter.
transmission electron microscope (TEM)
THERMAL ANALYSIS
Differential Scanning Calorimetry
Differential Thermal Analysis
TGA
TMA
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.
Differential scanning calorimetry (DSC)
In __, the material under study and an inert reference
are made to undergo identical thermal cycles,
DTA
In __, a sensitive balance is used to follow the
weight change of the sample as a function of
temperature.
TGA
measures the mechanical
response of a polymer system
as the temperature is changed.
Typical measurements include
dilatometry, penetration or
heat deflection, torsion
modulus, and stress-strain
behavior.
➢TMA
