Temperature modulated DSC for the multiple glass transition in poly(n-alkyl methacrylates)

Dielectric and mechanical relaxation processes in the series of poly(n-alkyl methacrylates) (PnAMA) depend systematically on the number of carbons in the alkyl part of the side chain. The crossover region of the dynamic glass transition shifts to lower frequencies for increasing this C number and reaches, above the hexyl member (C = 6), frequencies accessible to the temperature modulated DSC (TMDSC). The whole series from C = 1 (poly(methyl methacrylate), PMMA) to C = 11, the undecyl member is investigated by TMDSC and enthalpy retardation with DSC. The calorimetric result in the series are compared with the dielectric and mechanical data and are discussed with respect to the crossover region and a polyethylene-like glass transition (alpha(PE) process) due to a nanophase separation in these homopolymers. (C) 2002 Elsevier Science B.V. All rights reserved.