Crystallization of graft copolymers 1. Graft chains miscible with main chains

Abstract

Crystallization of graft chains was investigated using poly(methyl methacrylate)-graft-poly(ethylene glycol), in which poly(ethylene glycol) (PEG) is miscible with poly(methyl methacrylate) (PMMA). Various compositions of PEG (98, 83, 76 wt%) were used in poly(methyl methacrylate)-graft-poly(ethylene glycol) (GR98, GR83, GR76, respectively). More spherulites, that is, nucleations, were generated for GR98 than for the corresponding PEG/PMMA homopolymer blend having a corresponding blend composition. However, the growth rate G of spherulites was remarkably low for all graft copolymers. In the relationship between the value of G and the PEG composition, the extrapolation to pure PEG did not yield the G value for pure PEG. The apparent activation energy of crystallization was high for graft copolymers, which was attributed to a high large surface free energy due to the restriction of PEG chains by grafting. The rate of overall crystallization for GR98 was not very different from that for PEG/PMMA blends. The Avrami index for graft copolymers was similar to that for blends and for the PEG homopolymer. Both melting temperatures and degrees of crystallinity in the graft copolymers were depressed. In the blends of the graft copolymer with the PEG homopolymer, the G value of spherulites was governed by the G value of the PEG homopolymer. © The Society of Polymer Science, Japan (SPSJ) All rights reserved.