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 polymerization 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. When 2-(trimethylsiloxy)ethyl methacrylate (ProHEMA) was added to the living poly(BSMS) solution, block copolymerization started, to form poly(BSMS-b-ProHEMA), though prepoly(BSMS) remained to some extent in the mixture. Poly(BSMS-b-ProHEMA) yielded a tough membrane by casting from its toluene solution. Deprotection of trimethylsilyl groups was performed by soaking the poly(BSMS-b-ProHEMA) membrane in 0.1 N HCl/THF (15/1 (v/v)) solution for 72 h. From solid-state nuclear magnetic resonance 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 degrees C due to the glass transition temperatures, indicating that microphase separation was created in this membrane. The resulting membranes were fairly opaque and brittle. Based on scanning electron microscopy 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 obtained by deprotection from the membrane. The resulting membranes could have the possibility of applications in the biomedical field.