T.S.C. study of dielectric relaxation modes in P.M.M.A. as a function of tacticity

In stereoregular PMMA transitions and relaxations are strongly related. The study of dielectric loss (1) shows an α peak in the neighbourhood of 60°C for isotactic and 135°C for syndiotactic PMMA. Boyer and al. (2) have observed by D.S.C. that the glass transition temperature Tg is shifted from 55°C to 130°C and the liquid-liquid transition temperature T11 from 142°C to 174°c when the tacticity of the sample vary from isotactic to syndiotactic. The aim of this paper is to offer complementary data on Tβ, Tg and T11 by the method of thermostimulated current (T.S.C.) described by Bucci, Fieschi and Guidi (3). This method is very well adapted for the study of transitions in polymers.