Multidimensional Spectroscopy of Polymers. Vibrational, NMR, and Fluorescence Techniques

605 Pages·1995·46.88 MB·English

by  Marek W. Urban and Theodore Provder (Eds.)

ACS SYMPOSIUM SERIES 598
Multidimensional Spectroscopy
of Polymers
Vibrational, NMR, and Fluorescence
Techniques
1
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0
w
8.f
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5
0
5-
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19 Marek W. Urban, EDITOR
k-
1/b North Dakota State University
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1
0.
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oi: Theodore Provder, EDITOR
cs.org 995 | d The Glidden Company
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bs.5,
12 | http://pun Date: May
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2, 2cati Developed from a symposium sponsored
uly 2Publi by the Division of Polymeric Materials: Science
J and Engineering, Inc., at the 208th National Meeting
of the American Chemical Society,
Washington, D.C.,
August 21-25, 1994
American Chemical Society, Washington, DC 1995
In Multidimensional Spectroscopy of Polymers; Urban, M., et al.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1995.
QD 139 .P6M85 1995 copy 1
Multidimensional
spectroscopy of polymers
Library of Congress Cataloging-in-Publication Data
Multidimensional spectroscopy of polymers: vibrational, NMR, and
fluorescence techniques / Marek W. Urban, editor, Theodore Provder,
editor.
p. cm—(ACS symposium series, ISSN 0097-6156; 598)
"Developed from a symposium sponsored by the Division of Polymeric
Materials: Science and Engineering, Inc., at the 208th National Meeting
of the American Chemical Society, Washington, D.C., August 21-25,
1994."
1
0
0
w Includes bibliographical references and indexes.
8.f
59 ISBN 0-8412-3262-8
0
5-
9 1. Polymers—Analysis—Congresses. 2. Spectrum analysis-
9
1 Congresses. I. Urban, Marek W., 1953- . II. Provder, Theodore,
bk- 1939- . III. American Chemical Society. Division of Polymeric
1/ Materials: Science and Engineering. IV. Series.
2
0
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0. QD139.P6M85 1995
oi: 1 547.7Ό46—dc20 95-178C8I0P
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In Multidimensional Spectroscopy of Polymers; Urban, M., et al.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1995.
1995 Advisory Board
ACS Symposium Series
M. Joan Comstock, Series Editor
Robert J. Alaimo Cynthia A. Maryanoff
Procter & Gamble Pharmaceuticals R. W. Johnson Pharmaceutical
Research Institute
Mark Arnold
University of Iowa Roger A. Minear
University of Illinois
01 David Baker at Urbana-Champaign
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8.f Omkaram Nalamasu
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05 Arindam Bose AT&T Bell Laboratories
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9 Pfizer Central Research
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k-1 Vincent Pecoraro
1/b Robert F. Brady, Jr. University of Michigan
02 Naval Research Laboratory
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0. George W. Roberts
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oi: Mary E. Castellion North Carolina State University
12 | http://pubs.acs.org n Date: May 5, 1995 | d MNACUhanrateitvirmhoegnurEaasrdir ltei ByStt c. oC AifEeo n.Wml clCipeissaa cFnvooyanu nsniandu aagttih oM n adison JUDConoohnaivuctne guU rrlRsraritbe.sy na S Atno haTf. a -IeSCplclmhihlneanoiymotih lspo gaiiegsn Corporation
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2, 2cati Gunda I. Georg L. Somasundaram
uly 2Publi University of Kansas DuPont
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Madeleine M. Joullie Michael D. Taylor
University of Pennsylvania Parke-Davis Pharmaceutical Research
Lawrence P. Klemann William C. Walker
Nabisco Foods Group DuPont
Douglas R. Lloyd Peter Willett
The University of Texas at Austin University of Sheffield (England)
In Multidimensional Spectroscopy of Polymers; Urban, M., et al.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1995.
Foreword
THE ACS SYMPOSIUM SERIES was first published in 1974 to
provide a mechanism for publishing symposia quickly in book
form. The purpose of this series is to publish comprehensive
books developed from symposia, which are usually "snapshots
in time" of the current research being done on a topic, plus
some review material on the topic. For this reason, it is neces
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00 sary that the papers be published as quickly as possible.
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1/b round out the scope of the volume. In addition, a draft of each
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10. This anonymous review process is supervised by the organiz
oi: er^) of the symposium, who become the editor(s) of the book.
org 5 | d The authors then revise their papers according to the recom
acs.199 mendations of both the reviewers and the editors, prepare
12 | http://pubs.n Date: May 5, wvcaihemwoe crApahsa-e rpceaeka r drstyuh laaerct,e o a poliylnn n,lc yela ucnoeddrsei sgdsaui rniybna m lrt ehirtvee i stshevieaoo rnlcufshim nh aeaplvs a.ep p aebVpreseee rrnbsa namtdtoi a mdoth errie.ge pienrdaoildt ourrecs ,
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2, 2cati tions of previously published papers are not accepted.
uly 2Publi
J M Joan Comstock
Series Editor
In Multidimensional Spectroscopy of Polymers; Urban, M., et al.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1995.
Preface
WHILE CONTINUOUSLY CHANGING ELECTRONICS, computer, and sen
sor technologies open new opportunities in the development of chemical
instrumentation, new concepts in polymer analysis provide a powerful
means for expanding analytical resources. This interplay results in the
development of more sensitive and powerful techniques and has created a
new generation of hyphenated and multidimensional analytical
1
0 approaches. The hyphenated methods in polymer analysis were docu
0
pr mented in Hyphenated Techniques in Polymer Characterization: Thermal
8.
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5 and Other Instrumental Methods, ACS Symposium Series 581, and this
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5- volume focuses on multidimensional spectroscopic approaches in polymer
9
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1 analysis. Multidimensional analysis has been known for a long time, yet it
k-
1/b has revived in recent years.
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0 When two or more analytical techniques are tied together, which is
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10. commonly referred to as a hyphenated approach, a new level of under
oi: standing is achieved, resulting in a synergistic outcome of an experiment.
org 5 | d In contrast, if one considers a simple experiment in which spectroscopic
acs.199 analysis is performed as a function of time, concentration, or other addi
ubs.y 5, tive properties, the output will be multidimensional, and a number of
pa
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transform IR and Raman, NMR, and fluorescence spectroscopies, with
the focus on their multidimensional character and continuously increasing
sensitivity, appears to be inevitable.
This volume covers several aspects on multidimensional spectroscopic
analysis and focuses on Fourier transform IR, NMR, and fluorescence
spectroscopies in the analysis of polymers and multidisciplinary
approaches utilized in the analysis of polymers in various environments.
The book is divided into four sections describing the most recent develop
ments in each field. This choice was dictated by the importance of these
spectroscopic, molecular-level probes and their capabilities to enhance
our understanding of structure-property relationships in polymers.
ix
In Multidimensional Spectroscopy of Polymers; Urban, M., et al.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1995.
Acknowledgments
We thank all speakers of the International Symposium on Polymer Spec­
troscopy for their participation, and we thank the contributing authors to
this volume for their effectiveness and timely response to the deadlines. A
special note of appreciation goes to P. R. Griffiths of the University of
Wyoming, Klaus Schmidt-Rohn of the University of Massachusetts, and
Ian Sautor of the University of Lancaster, United Kingdom, for contribut­
ing introductory remarks for each book section.
The ACS Division of Polymeric Materials: Science and Engineering,
Inc., and the Petroleum Research Fund of the American Chemical
Society are gratefully acknowledged for the financial support of the sym­
posium.
1
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8.pr MAREK W. URBAN
59 Department of Polymers and Coatings
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5- North Dakota State University
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1 Fargo, ND 58105
k-
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0 THEODORE PROVDER
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0. The Glidden Company
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org 5 | d 16651 Sprague Road
acs.199 Strongsville, OH 44136
ubs.y 5,
12 | http://pn Date: Ma January 16, 1995
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In Multidimensional Spectroscopy of Polymers; Urban, M., et al.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1995.
Chapter 1
Fourier Transform IR and Raman
Spectroscopy of Polymers
Section Overview
Peter R. Griffiths1 and Marek W. Urban2,3
1Department of Chemistry, University of Idaho, Moscow, ID 83843
2Department of Polymers and Coatings, North Dakota State University,
1
0 Fargo, ND 58105
0
h
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59 When atoms become attached to each other through a formation of chemical
0
5- bonds, a molecule or macromolecule is formed. Because all atoms in a molecule
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19 possess kinetic energy, they vibrate. Such vibrations can be deconvoluted to so-called
k-
b normal vibrational modes, and classified into a few classes: some modes may be
1/
2 observed in the Raman spectrum, some in the infrared, and some may or may not be
0
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0. seen in either spectrum. When the molecule possesses a high degree of symmetry, there
1
oi: is a rule of mutual exclusion which states that no vibrational mode may be observed in
org 5 | d both the infrared and Raman spectra. This high symmetry is defined by a center of
cs.99 inversion operation. As the symmetry is reduced, and the molecule no longer contains
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2, 2cati change in the electron polarizability resulting from the movement of atoms. Thus, in
July 2 Publi foorldloewr ifnogr ian tgeigvreanls vmiburastti obnea nlo mt oeqduea tl oto b zee irnof.r ared and Raman active, respectively, the
The vibration is infrared active if
Here, [μ]ν',ν" is the dipole moment in the electronic ground state, Φ is the vibrational
eigenfunction and v' and v" are the vibrational quantum numbers before and after
transition, respectively, and Q is the normal coordinate of the vibration.
a
The vibration is Raman active if
3Corresponding author
0097-6156/95/0598-0002$12.00/0
© 1995 American Chemical Society
In Multidimensional Spectroscopy of Polymers; Urban, M., et al.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1995.
1. GRIFFITHS AND URBAN FTIR and Raman Spectroscopy of Polymers 3
Here, [α] is the polarizability tensor of the vibration, and the remaining parameters are
the same as for the infrared activity in equation 1. The apparent differences in the
principles governing both effects have led to the development of two physically distinct,
yet complimentary, experimental approaches to obtain infrared and Raman spectra. As
indicated in equation 2, the detection of Raman scattering involves a completely
different assemblage of principles. When monochromatic radiation at frequency v
o
strikes a transparent sample, the light is scattered. While most of the scattered light
consists of radiation at the frequency of the incident light referred to as the Raleigh
scattering, typically 1 out of 106 photons are scattered inelastically. This portion of the
scattering is referred to as Raman scattering. This inelastically scattered fraction of
light, composed of new modified frequencies (v + .V), is referred to anti-Stokes
o k
scattering, and (v - V) is the Stokes scattering component. Figure 1 illustrates a
o k
schematic diagram of the scattering processes leading to IR and Raman spectra. This
energy diagram shows that the anti-Stokes scattering requires that the molecules start
1
00 in an excited vibrational state. Because the easiest way to populate these excited
h
8.c vibrational states is by a thermal excitation, the anti-Stokes intensities will be very
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5 temperature dependent and typically quite weak at room temperature. Therefore,
0
5- Stokes scattering is the most common way to record Raman spectra. Figure 1 also
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1 illustrates that the absorption process observed in IR may, and under certain selection
k-
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02 scattering process.
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J of IR LIGHT hv = hv hv = h>o-hH hv = hv+fo>
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V
RAMAN SCATTERING
Figure 1. Schematic representation of IR absorption, Rayleight, Stokes, and anti-
Stokes scattering processes.
Infrared and Raman spectroscopy have gone through numerous stages of development.
At the early days, dispersive instruments dominated the field. When Fourier transform
infrared spectrometers utilizing interferometric detection were introduced, numerous
developments of sensitive techniques resulted. The sensitivity enhancements of
In Multidimensional Spectroscopy of Polymers; Urban, M., et al.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1995.
4 MULTIDIMENSIONAL SPECTROSCOPY OF POLYMERS
attenuated total reflectance (ATR), reflection-absorption (R-A), diffuse reflectance
(DRIFT), photoacoustic (PA), emission, or surface electromagnetic wave (SEW)
spectroscopies, and further developments of other experimental approaches were
primarily attributed to a higher energy throughput of interferometric instruments. A
schematic diagram of selected techniques, along with a brief description is given in
Figure 2.
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J Figure 2. Commonly used surface-sensitive infrared techniques: A - Single reflection-
absorption (R-A) setup; incident light (I) penetrates the sample and is reflected (R) by
the metal mirror (Θ should be between 75 and 89.5°); Β - single internal reflection;
incident light (I) passes through the internal reflection element and is totally reflected
(R) at θ > θο (ni and n2 are the refractive indices of the,sample and the internal element,
respectively); C - Multiple-reflection setup in attenuated total reflection (ATR) mode;
D - Diffuse reflectance (DRIFT) setup; the incident light (I) is diffusively scattered in
all directions (D), collected by hemispherical mirrors, and re-directed to the detector. Ε
- Emission setup; the source of IR light is replaced by a heated sample and emitted light
is analyzed by the infrared detector; F - Photoacoustic (PA) setup; the incident
modulated light with intensity Io impinges upon the sample surface; the light is
absorbed, and as a result of re-absorption, heat is released to the surface which, in turn,
generates periodic acoustic waves.
In Multidimensional Spectroscopy of Polymers; Urban, M., et al.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1995.
1. GRIFFITHS AND URBAN FTIR and Raman Spectroscopy ofPolymers 5
With this background in mind, and considering recent instrumental advances in infrared
and Raman spectroscopy, let us briefly outline the current developments in vibrational
spectroscopy utilized in the analysis of polymers.
Infrared spectroscopy has been used for the study of polymers for about half a
century. In about 1980, the Perkin-Elmer Corp., at that time the dominant
manufacturer of infrared grating spectrometers, estimated that about 80% of their sales
were for polymer-related applications. The advances in Fourier transform infrared (FT­
IR) spectroscopy that have been made since that time have given polymer scientists
significantly greater sensitivity and/or reduced measurement time. Furthermore, the
development of many different sampling accessories for these instruments, such as
those for attenuated total reflectance (ATR), specular reflectance (SR), reflection-
absorption (R-A) at near-normal and near grazing incidence, diffuse reflectance
(DRIFT), and photoacoustic (PA) spectroscopy, has increased the flexibility of FT-IR
1
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0 spectroscopy so that polymers of essentially any morphology can be investigated.
h
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8.
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05 Possibly the most important advance in sampling for infrared spectroscopy over
95- the last 15 years involves the development of microscopes for the mid-infrared region.
9
k-1 Not only can transmission spectra of samples as small as 10 μηι in diameter be
1/b measured, but other techniques such as ATR, SR, R-A, DRIFT, and even PA
2
0 spectroscopy have been applied to microscopically small domains and inclusions in
1
10. polymers. In the case of Raman microscopy, an approximate 1 μηι spatial resolution
oi: can be attained.
org 5 | d
cs.99 Using conventional rapid-scanning FT-IR spectrometers, static and dynamic
a1
ubs.y 5, molecular level information, with time resolution as short as ~50 ms, can be obtained
12 | http://pn Date: Ma fmsocoar ndpnuoilnlaytgem dse prsestrc atthrionamt o aenrt eethr sbe e hsinpavegce st rubabe joeefnc t pedodel ystimogn eaer sdg trtoahd abutea l alsyltluo idwnice rdteh.a eTs ihneefgfse esct tre afofinefc. tasR lcoeacwne- nbatmely cp,a liusttsueedpde-
0o by reversible changes in the crystallinity or orientation, or even bond angles in the
2, 2cati polymer. The phase lag of the infrared signal with respect to the applied strain can be
uly 2Publi considered to be analogous to the phase angle measured from a stress-strain curve
J measured by dynamic mechanical analysis (DMA). Since all infrared signals result from
vibrations originating from individual functional groups in the polymer, the data
obtained in such an experiment may be considered as a type of molecular-level DMA.
The absorptivities of fundamental modes that give rise to bands in the mid-
infrared spectrum are usually too high to permit samples much thicker than 100 μηι to
be investigated. In the situations when thin samples cannot be prepared, the near-
infrared (NIR) spectral region, where overtone and combination bands due to C-H, O-
H, and N-H groups absorb, becomes of great importance. NTR spectroscopy has,
therefore, become tremendously useful for measuring the spectra of thick samples,
especially in the field of process analysis where path-lengths less than 1 mm are often
difficult to achieve. Diffuse reflectance (DRIFT) is another technique where NIR
spectroscopy has proved to be beneficial. Because of the high absorptivities of
In Multidimensional Spectroscopy of Polymers; Urban, M., et al.;
ACS Symposium Series; American Chemical Society: Washington, DC, 1995.