The surface chemical modification of polyurethane (PU) films was performed by a UV laser-induced chemical reaction in a polysaccharide solution. This was undertaken with the possible application of hydrophilic packaging of implantable medical devices and in-vivo sensors. When a PU film in an aqueous alginic acid (AAC) solution was irradiated with the XeCl laser, it turned hydrophilic. Contact angles of water on the film were changed from 110$DGR to 60$DGR@. Since the absorption of AAC solution at 308 nm was negligibly small, the laser irradiation produced reactive sites solely on the PU surface, where AAC could be immobilized by chemical bonds. The mechanism for the modification was investigated by surface analyses with Fourier transform infrared spectroscopy and a photometric dye staining technique. This hydrophilic modification was interpreted as nanometer-scaled grafting of AAC induced by one-photon photochemical processes.
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