A Raman study of order in some complex polyesters

Abstract

The development of the Fourier Transform Raman spectrometer in the polymer field has substantially eliminated many of the difficulties previously encountered when using the conventional technique. Their sensitivity is such that the Raman spectra of a wide range of polymers, in the as-received form may be obtained in a few minutes, and with-out prior time consuming optimization of sample placement in the spectrometer. Furthermore the use of the 1.064µm line from a Nd³⁺:YAG laser as the excitation source has largely eliminated the fluorescence problem. This thesis describes the application of the technique to three very different polyester systems.

In Chapter 3 of the thesis the technique has been used successfully to monitor the autoxidative curing process of a commercially based Alkyd resin and its model compounds. FT-Raman showed the configurational changes occurring for the C = C bond {cis/trans isomerism, and conjugation) during autoxidation. In Chapter 4 a range of novel liquid crystalline polyesters have been analyzed by FTIR, FT-Raman spectroscopy, Differential scanning calorimetry, X-ray diffraction, and Thermo-optical analysis. Results have been compared and contrasted between the techniques, with an emphasis placed on the effects of lateral substituents and flexible spacer lengths.

Chapter 5 investigates the FT-vibrational spectra of amorphous vs crystalline polybutylene terephthalate and polybutylene terephthalate blended with an epoxy resin (synthesised from epichlorohydrin and diphenyl propane) over a range of cure times and temperatures. Phase separation under certain conditions has been reported.

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