Formation of stimuli-responsive surfaces by surface-initiated polymerization

Abstract

Part I. Thermoresponsive PNIPAAm films were grafted both on the glass substrate and polystyrene bead and then cell attachment and detachment were observed on each surface. The grafting amount of PNIPAAm on the glass substrate was fixed at 142 nm thick following our previous results with the gold substrate. The grafting amount of PNIPAAm on the polystyrene bead was varied from 0.1 M to 0.5 M to identify the optimum condition for cell-surface adhesion control. Cell attachment and detachment were finely observed on the PNIPAAm grafted glass slide. Through the cell attachment and detachment results on the PNIPAAm grafted polystyrene bead at different condition for polymerization differing the monomer concentration, we could find out the best condition for cell-surface adhesion control. Cell attachment and detachment were both highly efficient on the PNIPAAm film formed from 0.2 M concentration of monomer solution. Part II. We formed a thin film of diblock copolymers on gold by surface-initiated, ring-opening metathesis polymerization with $3^{rd}$ generation Grubbs catalyst, [($H_2$IMes)$(3-Br-py)_2-$(Cl)_2$Ru=CHPh]. Due to the high activity of the ruthenium catalyst, we successfully formed a thin film of well-defined block copolymers with endo-monomer and a mixture of endo- and exo-monomer. To form an amphiphilic block copolymer, the protected hydroxyl groups were deprotected and the hydrophilic groups were introduced to the first block. The deprotection led to the thin film formation of an amphiphilic diblock copolymer, which possessed both hydrophilic and hydrophobic blocks in the chain. The selective swelling of hydrophilic and hydrophobic blocks was observed after the treatment with different solvents, which was manifested by morphogical changes of surfaces.