The present invention relates to amphiphilic copolymer networks comprising polyisobutylene segments and poly(alkylene glycol) segments. The polyisobutylene segments of the amphiphilic networks are physically crosslinked by hydrophobic forces. The amphiphilic networks have particular use as coatings for biological implants. Also provided is a process for preparing a physically crosslinked amphiphilic copolymer network comprising: providing a block copolymer comprising polyisobutylene segments and poly(alkylene glycol) segments; introducing the block copolymer into an aqueous solvent; and allowing the block copolymer to self-assemble into physically crosslinked a copolymer network.