Surface grafting on polymer surface using physisorbed free radical initiators

A new strategy for creation of radicals on an inert polymer surface has been developed. This new method combines free radical polymerization with a surface graft polymerization. The polymer film, poly(dimethylsiloxane) (PDMS), was selected as an inert model material and was immersed into acetone containing azo-bis-isobutyrylnitrile (AIBN). We speculate that the AIBN becomes physically adsorbed or partially penetrates the hydrophobic polymer surface. The polymerization of water-soluble monomers was initiated by the absorbed initiator and polymer surface became modified by the hydrophilic monomers. We speculate this process was facilitated by the poor diffusion of physisorbed radicals derived from AIBN into an aqueous medium. ATR-IR, XPS, and contact angle measurements were used to characterize the surface modification. This method provides a potential modification method for the coating of many polymer surfaces possessing complicated geometrical shapes. The principle relies on the insolubility of the physisorbed initiator and the medium of the polymerization mixture.