ENTHALPY RELAXATION IN POLYMETHYL(ALPHA-N-ALKYL)ACRYLATES - EFFECT OFLENGTH OF ALKYL CHAIN

In this work, we have investigated by DSC the structural relaxation of amorphous polymethyl(alpha-n-alkyl) acrylates in which it is possible to change the length of the alkyl chain. We have evaluated the Naraya naswamy parameter, x, which controls the relative contribution of temp erature and of structure to the relaxation time, the apparent activati on energy, Delta h, and the nonexponentiality parameter, beta, of the stretched exponential response function. The results suggest that x i ncreases while Delta h decreases and beta remains constant as the len gth of the side chain increases. This allows us to comment on the effe ct of chemical modification on the relaxation kinetics. (C) 1998 John Wiley & Sons, Inc.