Surface property, ionic mobility and conformational stability of polymer hydrogels

Abstract

Chapter 1. In this study, we have XPS to elucidate the surface topography and copolymer composition of a series of poly($\alpha$-methylstyrene) (P$\alpha$-MS) and poly (2-hydroxyethyl methacrylate) (PHEMA) block copolymer films. Contact angle can be presented for block copolymers surface composition of P$\alpha$-MS/PHE-MA block copolymers at the air-polymer and the water-polymer interface. The results show that the P$\alpha$-MS concentration at the air-polymer interface is substantially higher than the known bulk concentration of P$\alpha$-MS. Whereas contact angle measurements at the water-polymer interface show the surface enrichment in copolymer of hydrophilic PHEMA. These results indicate that the P$\alpha$-MS/PHEMA block copolymer surfaces are not overlayer. By combining scanning electron spectroscopy (SEM), we see that surface topography of P$\alpha$-MS/PHEMA block copolymer matchs with bulk morphology. Models are presented for the 3-D morphology of the sample consisting of discrete regions of P$\alpha$-MS and PHEMA. Chapter 2. The addition of ureas as a class of denaturants is found to increase the degree of swelling of poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogels. Especially, in the concentration range of 3-4M urea, 2-3M methylurea, 1.5-2M 1,3-dimethylurea, and 1.5-2M tetramethylurea, the swelling of the PHEMA hydrogels is shown to increased markedly. Since the denaturing ability of ureas can change the random strutures in which nearly all constituents are exposed to solvent, we have been able to obtain the correlation between the degree of swelling and the hydrophobic components($\gamma_s^d$) to the total surface free energy for PHEMA hydrogels. The role the water plays in the conformational transition of the hydrogels is measured by the amount of bound water associated with a particular hydrophilic site in the PHEMA hydrogels. This result is consistent with the degree of swelling. It is not due to a simple urea-PHEMA interaction because the bou...