Thermally responsive poly(N-isopropylacrylamide) monolayer on gold: synthesis, surface characterization, and protein interaction/adsorption studies

This report describes a novel method for preparing a thermally responsive poly(N-isopropylacrylamide) (PNiPAM) monolayer on a gold surface, and demonstrates the function of this monolayer in aqueous media. Thiol (–SH) terminated PNiPAM was synthesized by UV polymerization followed by hydrolysis, and a monolayer of this polymer (2.84±0.2 nm) was prepared on a gold substrate by simply dipping a precleaned gold plate into an aqueous solution of the PNiPAM. Cyclic voltametry and atomic force microscopy studies showed that the gold surface was well covered by the PNiPAM chains, and X-ray photoelectron spectroscopic data showed that this monolayer was chemisorbed on the gold surface. Studies of the water contact angle, protein interaction, and protein adsorption on the PNiPAM monolayer demonstrated that this monolayer shows a temperature dependence of the interfacial properties in aqueous media.