PHASE-BEHAVIOR AND PHOTO-CROSS-LINKING KINETICS OF SEMIINTERPENETRATING POLYMER NETWORKS PREPARED FROM MISCIBLE POLYMER BLENDS

Mixtures of polystyrene derivatives (PSCS) and poly(vinyl methyl ether ) (PVME) were made photocrosslinkable by chemically labeling PSCS chai ns with photoreactive anthracene. Miscibility of these anthracene-labe led PSCS/PVME blends was examined by light scattering under several cr osslinking conditions in the one-phase region via photodimerization of anthracenes. As the reaction proceeds, the coexistence curve of PSCS/ PVME blends shifts toward the low temperature side. By following the c hanges in concentration of anthracenes with irradiation time, it was f ound that the crosslinking reaction of PSCS chains in the blends does not follow the mean-held kinetics. However, it can be well expressed b y the Kohlrausch-Williams-Watts (KWW) relaxation mechanism, indicating that the crosslinking reaction proceeds inhomogeneously in the blends . By scaling the reaction time with the average reaction rate obtained from the KWW equation modified for the reaction kinetics, all the cro sslinking data obtained in the miscible region of the reacted blends f all on a single master curve. These experimental results suggest the u niversal behavior of the photocrosslinking kinetics obtained under the ''shallow quench'' conditions in the region far away from the coexist ence curve of the reacting blends. (C) 1998 John Wiley & Sons, Inc.