Photon correlation spectroscopy of syndiotactic poly (n‐butyl methacrylate) near the glass transition

Abstract

Slow relaxing longitudinal density fluctuations in bulk syndiotactic poly (n‐butyl methacrylate) [PBMA] were studied by photon correlation spectroscopy as a function of temperature from 70 to 90°C. The shape of the light‐scattering relaxation function broadened as the temperature approached the glass transition (Tg = 55°C). The average relaxation time shifted with temperature, consistent with previous studies of PBMA. The relaxation functions were analyzed in terms of a distribution of relaxation rates. The calculated distribution was clearly bimodal and the shape altered with temperature. The higher frequency peak in the distribution corresponds well with previous mechanical and dielectric relaxation studies of the intramolecular relaxation of the acrylate ester side chain. The resolution of the distribution into two modes is due to a well‐defined side‐chain motion with relaxation strength comparable to the primary glass‐rubber relaxation. © 1994 John Wiley & Sons, Inc.

Photon correlation spectroscopy of bulk poly(n‐hexyl methacrylate) near the glass transition

“…The dynamics of bulk poly(alky1 methacrylates) have been studied extensively by photon correlation spectroscopy ( PCS).2-i T h e quantity that is eventually obtained by PCS is the normalized relaxation function, 4( t). Near the glass transition, the relaxation functions are observed to be highly n~n e x p o n e n t i a l .~ T h e average relaxation time, (7), defined as the integral of the relaxation function, is a strong function of temperature and shows non-Arrhenius behavior. The temperature dependence of ( T ) can be described by an empirical equation called the Vogel-Tammann-Fulcher (VTF)8 equation…”

“…Broader decays were observed as the temperature was lowered for poly(methy1 methacrylate) (PMMA),3 poly(ethy1 methacrylate) (PEMA),2 and poly(buty1 methacrylate) (PBMA). 7 The distribution of relaxation processes can be studied in term of the relaxation rates, r = 1 /~. The distribution function, G(I'), is defined by the relation A unimodal distribution has been seen for polystyreneg and poly(viny1 acetate)."…”

“…A clearly bimodal distribution of relaxation rates has also been observed for syndiotactic poly(n-butyl methacrylate) (PBMA). 7 Recently, a study of poly( n-hexyl methacrylate) (PHMA) by photon correlation spectroscopy has been published." Average relaxation times reported in that work changed with temperature in a manner inconsistent with previous dynamic mechanical measurements on PHMA.…”

“…The average relaxation time (7) obtained from KWW analysis of the photon correlation spectroscopy data of PHMA are plotted logarithmically against lOOO/T. The box symbols denote the average value for(7) and the values are within 95% confidence level.…”

Comparison of mechanical and dielectric relaxation processes in laser-deposited poly(methyl methacrylate) films

“…Experimental data about the dynamic processes in bulk materials in most cases are gained from dielectric spectroscopy that allows a broad range of frequencies and temperatures [1]- [3]. In addition, there have been various other experimental approaches such as photon correlation spectroscopy [4,5], multi-dimensional nuclear magnetic resonance [6,7] and mechanical spectroscopy [8]- [10], which are usually applied at constant temperature below and above the thermodynamic glass transition T g .…”