Ultraviolet radiation of short wavelength (UVC) induced-modifications in optical properties of PADC

The induced optical modifications of poly allyl diglycol carbonate (PADC), which used in fabrication of ophthalmologic lenses, exposed separately to ultraviolet radiation with a short wavelength of 254 nm (UVC) for different durations were investigated. Poly allyl diglycol carbonate (PADC) samples were exposed to UVC from a crossliker, thereafter the UV-Vis spectra were measured using dual beam UV-Vis spectrophotometer at room temperature. The UV-Vis spectra show that the poly allyl diglycol carbonate (PADC subjected to blue shift before a wavelength of 280 nm and red shift after 280 nm, moreover the absorbance is increased at wavelength of 280 nm. Meanwhile for visible spectra including Red, Blue, and Green, there was no significant change upon exposure to UVC. This behavior indicates the suitability to utilized PADC as a successful UVC blocker without change in the visible light transparency. An isosbestic point is observed in the UV-Vis spectra that shifted to shorter wavelength with increasing the exposure time. The direct and indirect band gaps of PADC were determined, it was found that the indirect and direct band gap decrease with the increase of the exposure time. The direct and indirect optical energy band gaps and the number of carbon atoms in a cluster with modified Tauc's equation are correlated with the exposure time to UVC, where the number of carbon atoms in a cluster increases with the decrease in the optical gap energy.