Hydrophilic surface coatings from acrylic block copolymer

The influence of polymer structure on hydrophilic coatings designed to minimize adhesion in aqueous environments has been investigated. We have developed coatings based on block copolymers consisting of water-insoluble poly(methyl methacrylate) (PMMA) blocks coupled to water-soluble poly(ethylene glycol) (PEG-acrylate) blocks. The PEG-acrylate blocks are immiscible with PMMA, so that the block copolymers form ordered morphologies in the melt state. Thin films of the copolymers can be easily applied to surfaces, giving hydrophilic surface coatings. Rheological measurements on bulk gels formed by diluting triblock copolymers with a solvent mixture that is selective for the midblock of the copolymers confirm our expectation that these triblock copolymers form thermally reversible gels under appropriate conditions. Swelling of these materials by water is highly dependent on the lengths of the PEG side chains. The rate dependence of swelling for triblock copolymers in water is measured by use of a quartz crystal microbalance and by ellipsometry. These films do not dissolve in water and their properties equilibrate within several hours. Direct measurements of adhesion between a model acrylic elastomer and various substrates in water are also carried out. Significant adhesion is observed between the elastomer and a PMMA homopolymer, but the adhesion energy between the elastomer and a triblock copolymer coating is essentially zero. Humidity effects on the adhesion of different materials to these hydrophilic coatings are investigated by using a hydrophobic poly(n-butyl acylate) (PnBA) lens and a hydrophilic gelatin lens. With regard to the anti-fouling behavior, the triblock copolymer dramatically enhances the microbial resistance of PMMA or silicon surfaces.