SILICON-CONTAINING BLOCK-COPOLYMER MEMBRANES

With a high-performance artificial lung as the goal, we synthesized AB -type amphiphilic block copolymers of organosilicon-containing styrene with 2-hydroxyethyl methacrylate (HEMA) via an anionic living polymer ization technique. Living poly[4-(bis(trimethylsilyl)methyl)styrene] ( poly(BSMS)) was prepared by an anionic polymerization technique using butyllithium as initiator in tetrahydrofuran (THF) at -74 degrees C. W hen 2-(trimethylsiloxy)ethyl methacrylate (ProHEMA) was added to the l iving poly(BSMS) solution, block copolymerization started, to form pol y(BSMS-b-ProHEMA), though prepoly(BSMS) remained to some extent in the mixture. Poly(BSMS-b-ProHEMA) yielded a tough membrane by casting fro m its toluene solution. Deprotection of trimethylsilyl groups was perf ormed by soaking the poly(BSMS-b-ProHEMA) membrane in 0.1 N HCl/THF (1 5/1 (v/v)) solution for 72 h. From solid-state nuclear magnetic resona nce analysis, it was confirmed that deprotection of the trimethylsilyl groups from poly(BSMS-b-ProHEMA) proceeded completely by this method. Differential scanning calorimetry measurements showed that poly(BSMS- b-HEMA) membranes exhibited two endothermic peaks around 70 and 110 de grees C due to the glass transition temperatures, indicating that micr ophase separation was created in this membrane. The resulting membrane s were fairly opaque and brittle. Based on scanning electron microscop y analysis of the block copolymer membrane thus obtained, microporous structures were observed on the surface and in the bulk. As a result, microporous membranes with microphase-separated structures were obtain ed by deprotection from the membrane. The resulting membranes could ha ve the possibility of applications in the biomedical field.