Effects of ultraviolet photon irradiation on the space charge accumulation properties of several biodegradable polymers

Five kinds of biodegradable polymers were irradiated for 30 minutes by ultraviolet photons from a KrCl excimer lamp. Space charge distribution profiles observed by the pulsed electroacoustic method were compared between the non-irradiated and irradiated samples. The absorption spectra as a function of wavelength obtained for the samples indicate intensive appearance of conjugated double bonds in the vicinity of the irradiated surface in all the biodegradable polymers. Molecular weight composition profiles observed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry show that the samples were decomposed by the irradiation. This decomposition seems to be responsible for the higher conductivity of the irradiated samples, which in turn results in the change of space charge distribution profiles.