In this study, the spontaneous formation of hydrogels from a water-soluble and amphiphilic ABA-Type block copolymer in an aqueous system was examined. The block copolymers were composed of poly(2-methacryloyloxyethyl phosphorylcholine) (MPC) as the B segment and poly(n-butyl methacrylate) (BMA) as the A segment. A two-step living radical polymerization of the corresponding monomers yielded a well-defined ABA-Type block copolymer. By regulating the polymerization degree of each segment, the water solubility and amphiphilic natures of the resulting block copolymer could be controlled. The block copolymers spontaneously formed hydrogels when the composition of water in the medium increased to 80 vol% in the water/ethanol mixture. This was due to molecular aggregation of the block copolymers driven by the hydrophobic interactions between the poly(BMA) segments in the polymer. This hydrogel formation depended on the composition and polymerization degree of the MPC units. The poly(MPC) also showed good biocompatibility, thereby rendering the block copolymers applicable for the immobilization of biological components such as antibodies and enzymes and the encapsulation of cells under mild conditions.
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