Highly Blood-Compatible Surface Consisting of a Silicon-Containing Block Copolymer with Supramolecular Structure

Abstract

With the aim of developing a high-performance membrane-type artificial lung, a novel silicon-containing hydrophilic-hydrophobic block copolymer was prepared using a living anionic polymerization technique. To introduce high oxygen permeability, poly(4-[bis (trimethylsilyl)methyl)styrene]) [poly(BSMS)] was employed for the hydrophobic segment. Poly(2-hydroxyethyl methacrylate) [poly(HEMA)] segment was chosen as a counterpart to maintain high blood compatibility. A poly(BSMS-block-HEMA) [BH(X), where X denotes the mole fraction of BSMS in the copolymer] membrane showed a clear separation of microphase structure when the mole fraction X was more than 30% (cast from toluene solution), while BH(10) showed no marked phase separation, when the respective polymer was cast from a dimethylformamide (DMF) solution. It should be noted that DMF is a poor solvent for the poly(BSMS) segment. From a dynamic light scattering measurement of a DMF solution of BH(10) (0.1% w/v), submicron-sized particles were observed. The BH(10) surface prepared from this DMF solution containing submicron particles showed unique characteristics. The wettability of the BH(10) membrane was much higher than that of the poly(HEMA) surface, despite the introduction of the hydrophobic polymer segment. The equilibrium water content of the BH(10) was also higher than that of poly (HEMA). This may be explained by the supramolecular structure of the BH(10) membrane derived from the particle-casting technique. Also surprising was that the BH(10) surface showed extremely high blood compatibility. Indeed, the rate of adhesion and activation of rabbit platelets on the surface was much lower than on poly(styrene-block-HEMA), which we have shown to have fairly high blood compatibility. From these results, it can be concluded that BH(10) is a promising candidate for a novel blood-compatible material for use in such applications as an artificial lung and as a nonthrombogenic coating material.