Polymer brush membranes for pervaporation and high capacity protein binding

Atom transfer radical polymerization (ATRP) of 2-hydroxyethyl methacrylate from the surface of porous alumina supports yields polymer-brush membranes that can be readily modified to control their properties. Derivatization of poly(2-hydroxyethyl methacrylate) (PHEMA) coatings with octyl, hexadecyl, or pentadecafluorooctyl side chains provides films that are sufficiently hydrophobic to allow highly selective pervaporation of volatile organic compounds from water. Moreover, the polymerization and derivatization reactions readily yield defect-free films with thicknesses of 200 nm or less, and this minimal thickness results in fluxes of ∼1.4 kg/m2h (0.05 wt% VOCs at 22 °C) through fluorinated films. These fluxes are generally an order of magnitude greater than those through high-performance poly(dimethyl siloxane) pervaporation membranes. The use of different monomers may further enhance the flux and selectivity of pervaporation membranes prepared by ATRP.; In related work, ATRP of PHEMA brushes inside the pores of alumina supports followed by functional ization of PHEMA with nitrilotriacetate-Cu2+ complexes yields membranes that adsorb proteins{09}via coordination of Cu2+ to histidine residues. Adsorption isotherms show that these membranes have binding capacities as high as 0.9 mg of bovine serum albumin (BSA) per cm2 of external membrane surface area (150 mg/cm3 of membrane), and breakthrough curves indicate that saturation of the membranes with BSA or myoglobin occurs in less than 15 min. Nine cycles of protein loading, elution, and membrane regeneration result in no detectable loss of binding capacity. The unusually high capacity of these membranes for rapid protein binding makes them attractive for applications such as purification of his tagged proteins.; Expansion on the protein adsorption work demonstrates that polymer brushes derivatized with Ni2+ complexes are very attractive for purification of his tagged proteins. Protein binding experiments with films on gold substrates show that PHEMA-NTA-Ni2+ brushes are capable of selectively binding large amounts (3.1 mug/cm2) of his tagged ubiquitin (HisU). Porous alumina membranes modified with derivatized brushes also show remarkable capacities (0.72 mg/cm2) for the binding of HisU. Most importantly, gel electrophoresis studies show that these high-capacity membranes are highly selective for purification of his tagged proteins. Even in a 20-fold excess of BSA, membranes gave 99% HisU.