Rheological and Thermal Properties of Narrow Distribution Poly(ethyl acrylate)s

In the present work, we characterize the rheological behavior of 10 nearly monodisperse poly(ethyl acrylate) samples, whose molar mass ranges from 1200 to 150 000 g/mol. The poly(ethyl acrylate)s were obtained by means of a controlled/living radical polymerization technique. The time−temperature superposition principle works, and the T dependence of the horizontal shift factor a Tr(T) is fairly well described by the Williams−Landel−Ferry law. Furthermore, the zero-shear viscosity dependence on the temperature, for all the investigated samples, has resulted to be well described by means of Vogel−Fulcher laws. The mass dependence of thermal parameters such as the Vogel temperature T 0 and the pseudo-activation energy T b has been worked out and compared to the mass dependence of the glass transition temperature T g. This leads us to propose here a coherent way to describe their behavior and estimate several microscopic parameters in terms of free volume. Moreover, the molar mass dependence of material parameters has been investigated. The zero-shear viscosity η at different temperatures has been evaluated, and the critical mass value has been found to be M c = 26 000 g/mol. The ratio between the critical M c and the entanglement mass M e has been found to be about 2.2 from the evaluation of the plateau modulus . A mass dependence analysis of the steady-state compliance has also been carried out from which the second critical mass M c ‘ is inferred.