Multiple Glass Transition and Nanophase Separation in Poly(n-alkyl methacrylate) Homopolymers

TLDR: In this article, three qualitatively different glass transitions are observed in the shear curves at 10 rad/s: the conventional α process in the C 5 members, and an additional polyethylene-like glass transition, αPE, in the c ≥ 3 members.

Abstract: Shear data in the temperature range from −145 °C to the flow zone are presented for the poly(n-alkyl methacrylate)s from methyl (C = 1) to lauryl (C = 12). Three qualitatively different glass transitions are observed in the shear curves at 10 rad/s:  (i) the conventional α process in the C 5 members, and (iii) an additional polyethylene-like glass transition, αPE, in the C ≥ 3 members. All three processes depend systematically on side chain length. Two alternative empirical pictures for the coexistence of two glass transitions are discussed:  (a) a static nanophase separation between main chains and side chains and (b) a dynamic heterogeneity with two different time and length scales.