Chemical modification of the internal surfaces of cylindrical pores of submicrometer size in poly(ethylene terephthalate)

Maekawa, Yasunari; Suzuki, Yasuyuki; Maeyama, Katsuya*; Yonezawa, Noriyuki*; Yoshida, Masaru

Chemical modification of the internal surfaces of cylindrical pores with sub-micrometer of pore diameter in PET film was examined. The modification involved the alkylation of the carboxylic acid on the surfaces with the alkylation reagent containing a fluorescent probe, and it was monitored by observing the change in fluorescent emission intensity. When the DMF solution of 4-(bromomethyl)-6,7-dimethoxycoumarin (BrCU), which bore a coumarin fluorophore, was introduced into the pores, the emission and excitation intensities of the membranes increased proportionally with increases of the pore surface areas. Fluorescent spots of about 300 nm in diameter, which were located at the positions of the pores, can be observed in the fluorescence microscope image of the membranes, indicating that highly concentrated fluorescent probes are chemically incorporated on the internal surfaces of the cylindrical pores with 210 nm in diameter in the membranes. In the reactions of the PET surfaces with BrCU, the fluorescent intensities increased with increases of the contact angles. This result indicates that the hydrophilicity of the internal pore surfaces can be qualitatively modified by controlling the change in the fluorescent intensities.