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Chemistry 5861 - Polymer Chemistry 1
Evaluation, Characterization, & Analysis of Polymers (Chapter 5 in Stevens)1
I Introduction
A) Requisite Information
1)
a)
b)
c)
d)
2)
a)
b)
c)
d)
e)
3)
a)
Molecular Weights
Distributions
i)
i)
ii)
iii)
i)
Single or Multiple Curves
MW Averages
Polydispersity Index
Molecular Weight Determination Methods in Section 2
Chemical Composition
Repeating Units
Side Chains
Crosslinking Groups
End Groups
Additives
identity
concentration
localization
Stereochemistry & Configuration
Are structures independent of MW and place in chain
random
1 The graphics in these notes indicated by “Figure/Table/Equation/Etc., x.x in Stevens” are taken from our lecture text: “Polymer Chemistry: An Introduction - 3rd Edition” Malcolm P. Stevens (Oxford University Press, New York,
©2002, Dr. Allen D. Hunter, Youngstown State University Department of Chemistry
Chemistry 5861 - Polymer Chemistry 2
ii)
iii)
iv)
i)
ii)
i)
ii)
iii)
some type of alternation
blocks
grafts
b)
c)
II
Stereoregular or Random Side Chains
tacticity
head/tail structures
Linear or Branched
branching topology
amount of branching
branch lengths
Chemical Methods of Analysis
A) Examples
1)
2)
a)
b)
c)
d)
e)
f)
Mostly of historical interest now
Head/Tail Structure of Vinyl Polymers
Poly(vinyl alcohol)
Oxidation by HIO4 or Pb(OAc)4
Head-Head links have 1,2-diols
These are cleaved by these strong oxidizing agents (eventually to terminal
carboxylic acids)
⇒ reduced average MW
⇒ reduced viscosity
1999).
©2002, Dr. Allen D. Hunter, Youngstown State University Department of Chemistry
Chemistry 5861 - Polymer Chemistry 3
g)
3)
a)
b)
4)
III
This experiment run in our Physical Chemistry Lab
Double Bond Location in Polydienes
Ozonolysis
i)
ii)
i)
ii)
Hydrolysis or polyesters, polyamides, etc.
1st O3, 2nd H2O
cleaves olefin links to ⇒ aldehyde and/or ketone groups
Polyisoprene
⇒ H(O)C-CH2-CH2-C(CH3)O as organic product
was how polyisoprene structure determined
Spectroscopic Methods of Analysis
Main Spectroscopic Methods A)
1)
B)
Table 5.1 in Stevens
Infrared Spectroscopy
1)
a)
2)
3)
Need change in dipole moment
i.e., asymmetric vibration modes
FT-IR Databases
Analysis by comparison to Model
Compounds
a) Figure 5.1 in Stevens
©2002, Dr. Allen D. Hunter, Youngstown State University Department of Chemistry
Chemistry 5861 - Polymer Chemistry 4
4) Spectral subtraction to observe minor species
a)
b)
5)
a)
b)
c)
C)
Figure 5.2 in Stevens
e.g., spectrum of crystalline
regions
Polymer Blends
To look for new interactions
From Polyblend spectrum
subtract that for the two homopolymers
the difference spectrum is that for any new chemical or physical interactions
Raman Spectroscopy
1)
a)
b)
2)
a)
b)
Need change in polarizability
i.e., symmetric vibration modes
∴ especially sensitive to vibrations with little or no change of dipole moments
i) e.g.,
C-C vibrations
cis-trans isomerism
sulfur crosslinks in rubber
Problems/Limitations:
Instruments relatively expensive
Raman method harder to apply to colored materials
©2002, Dr. Allen D. Hunter, Youngstown State University Department of Chemistry
Chemistry 5861 - Polymer Chemistry 5
D) NMR Spectroscopy
1)
2)
a)
Backbone & Side chain Structure
Tacticity Analysis in Solution
Isotactic PMMA
i)
i)
ii)
i)
Figure 5.3 in Stevens
b) Polypropylene
Figure 5.4 in Stevens
identification via model compounds
3)
a)
Solid State NMR
CP-MAS
Narrows the broad lines
characteristic of solid state NMR
©2002, Dr. Allen D. Hunter, Youngstown State University Department of Chemistry
Chemistry 5861 - Polymer Chemistry 6
ii)
iii)
iv)
Figure 5.5 in Stevens
Cross Polarization
E)
transfer of polarization from 1H
⇒ faster 13C relaxation
Magic Angle Spinning
Magic Angle - 54.7°
thousands of tens of thousands of Hz spin rate
Electron Spin Resonance, ESR, Spectroscopy
1)
2)
a)
b)
Requires Free Radical in Sample
Excellent for mechanistic studies
synthesis
degradation
3)
a)
F)
Figure 5.6 in Stevens
usually plotted in derivative mode
Other Methods
1)
2)
3)
UV-Visible Spectroscopy
Fluorescence
etc.
©2002, Dr. Allen D. Hunter, Youngstown State University Department of Chemistry
Chemistry 5861 - Polymer Chemistry 7
IV X-ray, Electron, and Neutron Scattering
Principles of Diffraction A)
1)
2)
a)
b)
c)
d)
3)
a)
b)
B)
1)
2)
C)
1)
2)
Figure 5.7 in Stevens
WAXS
Wide Angle X-Ray Scattering
i) coherent
increased crystallinity ⇒ sharper rings
orientation of crystallites ⇒ arcs & then spots
single crystal studies
SAXS
Small Angle X-Ray Scattering
incoherent
Electron Diffraction
need conducting polymer (or coated polymer)
TEM, Transmission Electron Microscopy
Neutron Diffraction
especially sensitive to proton positions
require a “cold” neutron source!
©2002, Dr. Allen D. Hunter, Youngstown State University Department of Chemistry
Chemistry 5861 - Polymer Chemistry 8
V Characterization & Analysis of Polymer Surfaces
A) Surface Analysis
1) Table 5.2 in Stevens
Attenuated Total Reflectance Spectroscopy, ATR B)
1) Figure 5.8 in Stevens
C) Electron Spectroscopy for Chemical Analysis, ESCA
1) ESCA
©2002, Dr. Allen D. Hunter, Youngstown State University Department of Chemistry
Chemistry 5861 - Polymer Chemistry 9
a)
b)
c)
d)
e)
also called XPS
i)
i)
i)
X-ray Photoelectron Spectroscopy
uses soft X-rays to detach electrons from surfaces
Binding Energy of Electron = hν - Emitted electron energy
valence electrons
⇒ chemical information
core electron
⇒ localized elemental analysis
f)
D)
Figure 5.10 in Stevens
Secondary-Ion Mass Spectrometry, SIMS, and Ion-Scattering Spectroscopy, ISS
1)
2)
Figure 5.12 in Stevens
Identification of Surface
Species
©2002, Dr. Allen D. Hunter, Youngstown State University Department of Chemistry
Chemistry 5861 - Polymer Chemistry 10
Atomic Force Microscopy E)
1)
2)
3)
VI
Figure 5.14 in Stevens
in physical contact with surface
surface does not need to be
conducting
Thermal Analysis
Differential Scanning Calorimetry, DSC, & Differential Thermal Analysis, DTA A)
1)
2)
a)
b)
c)
3)
a)
b)
4)
a)
b)
c)
DTA is older technique now generally replaced by DSC
Sample heated and heat flow watched
typically in an inert atmosphere
typically wrt. to a reference sample
0.5 to 10 mg samples sizes typical
DTA
sample and reference heated by same source
∴ measure difference in temperature
DSC
sample and reference heated separately
different currents applied to keep same temperature
differences in applied current reflect differences in thermal properties
5) Figure 5.15, 5.16, 5.17, & 5.18 in Stevens
©2002, Dr. Allen D. Hunter, Youngstown State University Department of Chemistry
Chemistry 5861 - Polymer Chemistry 11
B) Thermomechanical Analysis, TMA, Dynamic Mechanical Analysis, DMA
1)
2)
C)
A probe is in contact with the sample
Detects phase transitions by change in modulus or volume
Thermogravimetric Analysis, TGA
©2002, Dr. Allen D. Hunter, Youngstown State University Department of Chemistry
Chemistry 5861 - Polymer Chemistry 12
1)
a)
b)
c)
d)
e)
Measures weight changes on heating
depolymerization
oxidation
desolvation
additive loss
etc.
2)
3)
a)
Figure 5.19 in Stevens
Often hyphenated technique
TGA-MS
i) Figure 5.20 in Stevens
b)
c)
d)
VII
TGA-FTIR
TGA-MS-FTIR
etc.
Measurement of Mechanical Properties
Instron Mechanical Tester A)
1) Figure 5.22 and 5.23 in Stevens
©2002, Dr. Allen D. Hunter, Youngstown State University Department of Chemistry
Chemistry 5861 - Polymer Chemistry 13
©2002, Dr. Allen D. Hunter, Youngstown State University Department of Chemistry
VIII
Evaluation of Chemical Resistance
A) Evaluation
1)
2)
IX
Predictable from chemical reasoning when wetting, pores, etc., taken into account
tested by immersion
Evaluation of Electrical Properties
A) Resistivity
1) Inverse of Conductivity
2) Figure 5.24 in Stevens
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