Stainless steel surfaces with thiol-terminated hyperbranched polymers for functionalization via thiol-based chemistry

Hyperbranched polyethyleneimine (BPEI) was coupled to a polydopamine-coated stainless steel (SS) substrate. Subsequent mercaptoethylation of BPEI with ethylene sulfide produced thiol functional groups on the SS surface. Functionalization of the surface was achieved by end-capping of the hyperbranches with organic molecules via thiol-based chemistry, including thiol–epoxy coupling, thiol–ene radical photo-addition and thiol–Michael addition. The SS-P(HEMA-b-SBMA) surface was prepared via thiol–ene radical photo-addition of the hyperbranches with an alkene-functionalized poly(2-hydroxyethyl methacrylate) (alkene-PHEMA) from atom transfer radical polymerization (ATRP) and subsequent block copolymerization of the zwitterionic monomer, N-(3-sulfopropyl)-N-(methacryloxyethyl)-N,N-dimethyl ammonium betaine (SBMA). The SS-PPEGMA and SS-PMETA surfaces were prepared, respectively, by thiol-initiated photopolymerization of poly(ethylene glycol)methyl ether methacrylate (PEGMA) and 2-(methacryloyloxy)ethyl trimethylammonium chloride (META). The antifouling SS-P(HEMA-b-SBMA) and SS-PPEGMA surfaces exhibit resistance to bacterial adhesion, while the SS-PMETA surface is bactericidal. Metal surfaces with thiol-terminated hyperbranches thus provide a versatile platform for tailoring surface functionalities.