Static and dynamic light-scattering studies of poly(vinyl acetate) in the glass transition region

Abstract

An optically clear sample of undiluted poly(vinyl acetate) (PVAc) has been prepared by UV-initiated bulk polymerization of monomer at 42°C. Measurements of light-scattering intensities in the temperature range T_g − 30°C > T > T_g + 50°C have been carried out. Photon correlation spectroscopy has been performed in the temperature range T_g + 5°C > T > T_g + 23°C. Intensity data for T < T_g are in agreement with the Einstein–Smoluchowski expression for density fluctuations, >δρ²; below T_g statistical thermodynamic formulation of >δρ², evaluated using experimental equation-of-state information, is found to be in accord with the light-scattering results. Photon correlation functions are well described by a single Williams–Watts function. Mean relaxation times and associated activation energies are compared with results of other relaxational studies of PVAc. Discrepancies observed are interpreted to be due in part to variability of sample histories as well as to problems in analytical treatment of the pertinent relaxation spectra.