Downloaded by UNIV OF MISSISSIPPI on June 18, 2015 | http://pubs.acs.org Publication Date: May 5, 1993 | doi: 10.1021/ba-1993-0236.ch001
1 Fourier Transform Infrared and Fourier Transform Raman Spectroscopy of Polymers Principles and Applications Marek W. Urban Department of Polymers and Coatings, North Dakota State University, Fargo, N D 58105
This chapter covers the fundamental principles and current applications of Fourier transform (FT) infrared and Fourier transform Raman spectroscopies as utilized in the analysis of polymeric materials. The primary emphasis of the first part is on the principles and advantages of these interferometric methods, whereas the remaining sections illustrate numerous applications focusing on the structure-property considerations in polymers. Particular attention is given to the most recent developments in FT analysis and includes examples of structural and conformational analysis of polymers, biological studies, and the applications of FT infrared and Raman microscopy to remote measurements. The differences and the complementary nature of infrared and Raman spectroscopies are also presented.
EJXPERIMENTAL SCIENCES HAVE BEEN PROFOUNDLY INFLUENCED b y the development o f novel instrumentation. V i r t u a l l y a l l scientific instrumentation is n o w u n d e r c o m p u t e r control, a n d sophisticated, faster data collection allows scientists to channel their resources m o r e effectively t o w a r d particular goals. T h e sophistication o f ma ny current physical approaches mandates the use o f h i g h l y sensitive, fast instruments a n d reasonably p o w e r f u l data acquisi tion computers to attain insights about fundamental aspects o f processes u n d e r investigation. Examples o f such sophisticated interplay are i n f r a r e d a n d 0065-2393/93/0236-0003$ 10.50/0 © 1993 American Chemical Society
In Structure-Property Relations in Polymers; Urban, M., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1993.
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STRUCTURE-PROPERTY RELATIONS IN POLYMERS
R a m a n spectrometers, w h i c h , used i n conjunction w i t h the fast F o u r i e r transform ( F T ) algorithms, are key instruments i n m o d e r n vibrational spec troscopy. This chapter w i l l first review the fundamental principles that govern infrared and R a m a n activity a n d then discuss the principles and applications o f F T detection i n vibrational spectroscopy.
Downloaded by UNIV OF MISSISSIPPI on June 18, 2015 | http://pubs.acs.org Publication Date: May 5, 1993 | doi: 10.1021/ba-1993-0236.ch001
Infrared and Raman Processes T h e n o r m a l modes o f vibration of any molecule can be d i v i d e d into three classes. Some modes may be observed i n the R a m a n spectrum, some i n the infrared, a n d some may not be seen i n either spectrum. F o r a molecule that possesses a h i g h degree o f symmetry, the rule of m u t u a l exclusion states that no vibrational m o d e may be observed i n b o t h the infrared and R a m a n spectra. This h i g h symmetry is defined b y a center of inversion operation. A s the symmetry is reduced, a n d the molecule no longer contains a center of inversion, some vibrational modes may be seen i n b o t h the infrared and i n the R a m a n spectra. H o w e v e r , the m o d e w i l l often have quite different intensity i n the two spectra. T h e q u a n t u m mechanical selection rules state that observation of a vibrational mode i n the infrared spectrum requires a change i n dipole m o m e n t d u r i n g the vibration. I n other words, the vibration is i n f r a r e d active i f the following condition is fulfilled:
[μ]^» Φ f «Μρ )μ
