Synthetic hydrogels: 7. High EWC semi-interpenetrating polymer networks based on cellulose esters and N-containing hydrophilic monomers

Abstract

The formation of high (> 70%) water content semi-interpenetrating polymer networks (IPNs) from combinations of cellulose esters and nitrogen containing hydrophilic vinyl monomers has been investigated. The properties of the resultant materials have been compared with those of copolymers of the same nitrogen containing monomers with a variety of methacrylate esters. Cellulose acetate and cellulose acetate butyrate were found to show acceptable solubility in the liquid monomers N, N-dimethyl acrylamide and N-vinyl pyrrolidone, which both possess adequate hydrophilicity, solvent power and polymerizability for IPN formation. In general the IPNs produced from the cellulose esters were observed to have higher equilibrium water contents than did the copolymers derived from the methacrylate monomers of similar hydrophilicity. Additionally, the detailed water binding properties of the two types of system showed considerable differences. Interpenetrating network formation produces materials that are stiffer and stronger but less elastic than the hydrogel copolymers of similar water content. In this behaviour these simple IPNs begin to mimic properties of biological hydrogel composites which differ from homogeneous synthetic hydrogels in the same way. The surface properties of the semi-interpenetrating materials are consistently different from those of the copolymers of comparable composition or equilibrium water content in that they have appreciably lower polar components ( γ p) of surface energy.