Evidence of two relaxation processes in the photon correlation spectra of poly(methyl methacrylate) above <i>T</i>_<i>g</i>

Abstract

Abstract Photon correlation functions of a high‐molecular‐weight PMMA ( M w = 1.06 × 10 7 , M n = 2.2 × 10 6 , T g = 103°C) have been studied in the temperature range 98 − 149°C. In contrast to previous results, two relaxation modes are observed in relaxation functions. The observed relaxation functions of PMMA are analyzed for the first time in terms of a continuous spectrum representing the distribution of retardation times. Using a modified computer program originally developed by Provencher, we have computed the spectrum of retardation times at various temperatures. The appearance of two distinct relaxation modes is clearly evident in the distribution of the retardation times and in the time correlation functions below 123°C.