AMPHIPHILIC NETWORKS .6. SWELLING AND SUSTAINED-RELEASE OF POLY(N,N-DIMETHYLACRYLAMIDE)-L-POLYISOBUTYLENE, POLY (N-N-DIMETHYLAMINO ETHYLMETHACRYLATE)-L-POLYISOBUTYLENE AND POLY(2-HYDROXYETHYL METHACRYLATE)-L-POLYISOBUTYLENE NETWORKS

The swelling behavior in water of three amphiphilic networks, poly (N,N-dimethylacrylamide)-l-polyisobutylene (DMAAm-l-PIB), poly(N,N-dimethylamino ethylmethacrylate)-l-polyisobutylene (PDMAEMA-l-PIB), and poly (2-hydroxyethyl methacrylate)-l-polyisobutylene (PHEMA-l-PIB), of various compositions was investigated. The PDMAAm-l-PIB and PHEMA-l-PIB networks displayed a distinct swelling front during swelling in water, suggesting polymer-relaxation controlled swelling. In contrast, PDMAEMA-l-PIB networks, in this solvent showed diffusion-controlled swelling most likely due to the relatively low T(g) and high hydrophilicity of the PDMAEMA moiety. The kinetics of theophylline release from initially dry networks exhibited Fickian or anomalous behavior depending on the crosslink density, the respective molecular weight of the hydrophilic/hydrophobic chains, and the overall composition of the networks.