The development of the dynamic glass transition in poly(n-alkyl methacrylate)s is investigated with broad-band dielectric spectroscopy in the frequency range from 10-4 to 109 Hz. The experimental data were analyzed by adjustment with one or a sum of two Havriliak Negami functions. Upon decreasing the temperature, the high-temperature relaxation (a) changes into the local β relaxation (Johari Goldstein mode), and the cooperative α relaxation sets in close to this aβ transition. For poly(n-butyl methacrylate) a separate onset (zero intensity) of the α process and a parallel course of both traces in the Arrhenius diagram were observed. The activation energy of the β process does not change in spite of the parallel development of the α process. On the other hand, for poly(ethyl methacrylate) the α onset is close to a bend in the local process, i.e., the activation energy of the latter changes after the α onset. In both materials the intensity of the α process linearly increases with falling temperatures but with different intensity. Several scenarios for the αβ-splitting region are suggested.

Heat capacity spectroscopy measurements in the frequency range from 1.25 to 12 600 rad/s at the dynamic glass transition in poly(vinyl acetate) are reported. The data are compared to results of dielectric and shear spectroscopy in a comparable frequency range on the same sample. The peaks of the different imaginary parts do not have the same position across the main transition zone. The sequence of the peaks with increasing frequency is as follows: dielectric compliance, entropy compliance, and shear modulus. The distances between the different peaks are 0.3 ( 0.4 and 1.0 ( 0.4 frequency decades, respectively.