Synthesis of central functionalized asymmetric triblock copolymers for surface modification and switchable surface properties

Well-defined central functionalized asymmetric triblock copolymers (CFABC) were designed as a new type of polymer-brush surface modifier with a short central functionalized block that could form chemical bonds with a suitable substrate surface. A combination of sequential living anionic polymerization and polymer modification reactions was used for the synthesis of two CFABCs: polystyrene-b-poly(4-hydroxystyrene)-b-poly(methyl methacrylate) (3) and polystyrene-b-poly(4-urethanopropyl triethoxysilylstyrene)-b-poly(methyl methacrylate) (4). The central block of 3, poly(4-hydroxystyrene), was synthesized with a protected monomer, p-[(tert-butyldimethylsilyl)oxy]styrene, for the polymerization step, and this synthesis was followed by the hydrolysis of the silyl protecting group. To obtain polymer 4, the phenol functionality in 3 was converted to triethoxysilyl groups by a quantitative reaction with isocyanato propyl triethoxysilane. Gel permeation chromatography and NMR characterization indicated that the block copolymers possessed controlled molecular weights and narrow molecular weight distributions. Preliminary atomic force microscopy and X-ray photoelectron spectroscopy analysis of the polymer brushes were reported.