Local and global motions in concentrated solutions of poly(methyl methacrylate)/bis(2-ethylhexyl phthalate)

Abstract

Photon correlation spectra (PCS) of the polarized and depolarized component of the scattered light have been recorded in concentrated solutions of low molecular weight poly(methylmethacrylate) (PMMA) in bis(2 ethylhexyl phthalate) (DOP), in the temperature range 250–360 K. At high temperatures, T, above, the glass transition temperature, T ng, PCS probes the concentration fluctuations, whereas at lower T the faster density fluctuations also appear in the same time window. Near T g, the PCS in the depolarized mode detects orientation fluctuations in the mixture that exhibit very broad distributions of relaxation times ( β KWW ≈ 0.2). The results are described in terms of the Kohlrausch-Williams-Watts (KWW) relaxation function and discussed in terms of the coupling scheme of relaxation.