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Infrared Spectroscopy in Analysis of Polymer Degradation

Polymers and Rubbers

  1. Michele Edge

Published Online: 15 SEP 2006

DOI: 10.1002/9780470027318.a2013

Encyclopedia of Analytical Chemistry

Encyclopedia of Analytical Chemistry

How to Cite

Edge, M. 2006. Infrared Spectroscopy in Analysis of Polymer Degradation. Encyclopedia of Analytical Chemistry. .

Author Information

  1. Manchester Metropolitan University, Manchester, UK

Publication History

  1. Published Online: 15 SEP 2006

Abstract

Infrared (IR) spectroscopy locates the spectral position (frequency) and intensity of absorbed (or emitted) radiation arising from molecular transitions between quantum states associated with the vibrations and rotations of specific chemical groups. Using this technique both qualitative and quantitative information can be obtained on changes in the composition of polymers during degradation. The use of mathematical data-processing techniques and instrumental attachments has enabled considerable progress to be made in this field,1–3 where changes to the composition of the polymer structure are invariably complex. In conventional IR spectroscopy the light is dispersed and each wavelength is examined separately, whereas the main advantage of Fourier transform infrared (FTIR) spectroscopy is that the signal is multiplexed and each point of an interferogram contains information on all the wavelengths present, enabling all frequencies to be determined simultaneously. The increased speed and higher signal-to-noise ratio of FTIR spectroscopy is the prime advantage in the analysis of complex materials. The use of computational software to obtain difference or derivative spectra enhances the dynamic range. This is of particular value when monitoring polymer degradation, where the main interference is from the nondegraded structure of the polymer. The main disadvantage of IR spectroscopy in identifying and quantifying the functional group changes that take place during polymer degradation is that broad and rather featureless bands are frequently produced. As a consequence it is necessary to resolve individual components by subjecting the sample to a prior chemical treatment, or by the use of coupled instrumentation.