Hydrophilic Surface Coatings from Acrylic Block Copolymers^†

A variety of hydrophilic acrylic copolymers have been synthesized and evaluated for their use as hydrophilic surface coatings. The polymers are based on an acrylic backbone onto which oligomeric analogues (degrees of polymerization of 1, 2, or 3) of monomethoxy poly(ethylene glycol) (PEG) have been grafted. The polymers are formed by transesterification of anionically polymerized poly(tert-butyl acrylate). Because acrylic acid groups are introduced during the conversion process, these polymers are actually random copolymers of a PEG−acrylate and acrylic acid. These random copolymers are hydrophilic and water-soluble. Triblock copolymers with these random copolymers as the midblock and poly(methyl methacrylate) (PMMA) end blocks have also been synthesized. The hydrophilic polymers corresponding to the midblocks are immiscible with PMMA and have surface energies which are comparable to PMMA. Spun-cast films of the triblock copolymers do not dissolve in water and are quite hydrophilic, as determined by contact angle measurements with water. Direct measurements of adhesive interactions in water show that the block copolymer coatings are able to completely eliminate adhesive interactions in an aqueous environment. Studies of the gelation process of the triblock copolymers in water/ethanol mixtures have also been performed in order to characterize the self-assembly of these materials into physically cross-linked gels.