Formation of Photo-Responsive Surfaces by Surface-Initiated Ring Opening Metathesis Polymerization and Atom Transfer Radical Polymerization: Reversible Optodes for Metal Ion Sensors

Abstract

In this work, we report on the grafting of photochromic polymer brushes from oxide surfaces using surface-initiated ring-opening metathesis polymerization (ROMP) and atom transfer radical polymerization (ATRP). The spiropyran-based homopolymers were synthesized from norbornyl derivatives of spiropyran using ROMP in the presence of Grubbs Generation II catalyst, whereas copolymers of methacrylate based spiropyran (SPMA) and different methacrylate derivatives were synthesized using surface-initiated ATRP. In both cases, polymer growth was monitored by ellipsometry and atomic force microscopy (AFM). For polymer brushes prepared by ROMP, the growth of the polymer film is strongly influenced by the monomer: catalyst ratio as well as reaction time. Reaction conditions were optimized to provide brushes with controllable thickness up to 120 nm. For copolymers prepared by ATRP, the polymerization proceeds in a living fashion, and copolymer brushes with thickness up to 80 nm were prepared. These densely packed and highly smooth polymer films were successfully used as surfaces with switchable wettability. Also, these films were used as reversible, photoswitchable optical sensors that show selectivity for different metal ions. Covalently bound polymer chains allow for an increase in sensor stability, impart a rapid response to analyte, and provide reversible, switchable sensor surfaces with longer lifetimes.