Photocontrolled gating by polymer brushes grafted on porous glass filter

Polymethacrylate-containing spiropyran was grafted on a glass filter to control permeation of organic liquid by photoirradiation. The glass filter was at first coupled with octadecyldimethyl-N,N-diethylaminosilane and next subjected to glow-discharge treatment for graft copolymerization of spiropyran-substrated methyl methacrylate (SPMA), (1-(beta-methacryloylethyl)-3,3-dimethylindoline-2,2'- spiro-6'-nitrospirobenzopyran, and methyl methacrylate (MMA). The surface modifications were monitored by X-ray photoelectron spectroscopy. The surface wettability was altered by these treatments. An SPMA/MMA copolymer in toluene was soluble under irradiation of ultraviolet light but was insoluble under irradiation of visible light, while the copolymer was soluble in N,N-dimethylformamide (DMF) irrespective of photoirradiation. Toluene permeation through a glass filter grafted with SPMA/MMA copolymer increased by ultraviolet-light irradiation, and decreased by visible-light irradiation. DMF permeation did not depend on the photoirradiation. These results demonstrated that the permeation of organic liquid through a glass filter can be controlled by the solubility, i.e., the extension/contraction of polymer chains grafted on the surface.