Interaction of water with syndiotactic and isotactic poly(2-hydroxyethyl methacrylate) studied by NMR and DSC

Abstract

Waters are classified by the interaction with poly(2-hydroxyethyl methacrylate) [PHEMA], using such adjectives as "bulk," "bound" and "interfacial." Because the conformation of syndiotactic-PHEMA is different from that of isotactic-PHEMA, the amounts of bound water in these polymers are not same. The nature and states of bound water in these polymers were studied by differential scanning calorimetry (DSC). The thermal studies showed no endotherm peak for ice melting in the lower watewr content (bound water region); there are two endotherm peaks for higher water content polymers near $0\,^\circ\!C$. The amounts of bound water in these polymers were determined from a quantitative analysis of endotherms of water melting transitions. These results show that isotactic-PHEMA contains more bound water than syndiotactic-PHEMA. The spin-lattice relaxation time(T$_1$) of deuterium for bound water in these polymers is measured to investigate the molecular motional characteristics and tactic effect of PHEMA. The bound water in isotactic PHEMA has longer spin-lattice relaxation time than that of syndiotactic PHEMA. Therefore, the interaction of bound water with syndiotactic PHEMA is stronger than that of bound water with isotactic PHEMA.