Creation of stable poly(ethylene oxide) surfaces on poly(methyl methacrylate) using blends of branched and linear polymers

Thin film miscible blends of poly(methyl methacrylate) (PMMA) and a branched random copolymer of methyl methacrylate and methoxy poly(ethylene glycol) monomethacrylate, P(MMA-r-MnG), were investigated by neutron reflectivity. The branched copolymer, which has a higher surface tension than PMMA, was nevertheless found to segregate to and completely cover both the surface and silicon substrate following annealing in 2000 Angstrom thick films with greater than or equal to 2 wt % P(MMA-r-MnG). This is in contrast to linear polyethylene oxide, which was depleted at both film interfaces when blended with PMMA and annealed. The reflectivity results were confirmed by contact angle studies, which indicate that the surfaces of P(MMA-r-MnG)/PMMA blends behave like that of pure P(MMA-r-MnG), resulting in a hydrophilic surface that is stable against dissolution in water-based environments. The branched hydrophilic additive is further shown to render PMMA resistant to protein adsorption and cell adhesion.