Effect of UV-Irradiation on Fluorescence of Poly (Para-Ethoxystyrene) Films with Phthalate and Terephthalate Plasticizers

Abstract

The photodegradation of irradiated thin films of poly (para-ethoxystyrene) with 265 nm radiations in the presence of air and as a function of irradiation time has been studied using UV-VIS, fluorescence and FT-IR spectroscopic techniques. The increase in irradiation time caused an increase in the intensity of the absorption band of the polymer, thus indicating a possibility of photodegradation of polymeric chains. The influence of increase in irradiation times on pure poly (ethoxystyrene) films caused a decrease in the intensity of the fluorescence band and the appearance of new broad band at longer wavelength and to decrease with increase in irradiation time. The influence of added phthalate and terephthalate plasticizers on photo-oxidative degradation was also investigated, and found to increase the photodegradation processes in polymeric chains. The photo-quenching rate constant was found to increase with the increase of the molar mass and bulkiness of the used plasticizers and to increase with the increase in irradiation time. The rate constant of the photo quenching process was found to decrease with the increase in the amount of added plasticizers, indicating that the added plasticizers may act as UV-absorbers which inhibit the photodegradation process. The analysis of the FT-IR spectra of the irradiated and non-irradiated samples, showed a noticeable formation of new bands, and their intensity was found to increase with the increase in irradiation time and also with the increase in the amount of added plasticizer. In addition, the observed increase in the intensities of the carbonyl and hydroxyl absorption regions of the FT-IR spectra, provide evidence for the photodegradation as well as photo-oxidation of polymeric chains.