The UV irradiation and blending effects on stability of Poly(Fluorostyrene) isomers in solution were studied at different intervals of irradiation time in presence of air. The increase in irradiation time of these isomers caused an increase in the intensity of the absorption band and an increase in the intensity of the absorption of new broad band at longer wavelength, thus indicating a possibility of photodegradation of polymeric chains. The influence of added dioctyl phthalate and dioctyl terephthalate plasticizers on photooxidative degradation was also investigated and was found to increase the photodegradation processes in polymeric chains. On the other hand, the intensity of excimer and monomer fluorescence bands maxima was also found to decrease with increase in irradiation times. These changes may be attributed to the formation of new photoproducts resulted from the photodegradation of irradiated polymeric chains. The decrease in polarity of used solvents caused a considerable enhancement to the intensity of the polymer fluorescence band and accelerated photodegradation. A proposed mechanism is suggested to account for the effects of added plasticizers, the increase in irradiation time, and polarity of solvents on photodegradation and photooxidation processes in polymeric chains. 1. Introduction The irradiation effects on stability of polystyrene [1–5] and substituted polystyrene [6–10] in solutions have been extensively studied by both theoretical and experimental approaches. The irradiation effect of halogenated polymers received a considerable attention, owing mainly to their industrial importance [11–13]. The photodegradation behavior of halogenated polystyrene has been found to be closely analogous to that of polystyrene [13, 14], and the mechanism of photodegradation of substituted polystyrene depends upon the structure and state of the polymer [15, 16]. Hence, the mechanism of polystyrene degradation in solution depends upon the mobility of free radicals among solvent molecules and is affected by the polarity of the solvent molecules [16, 17]. The photodegradation of polymeric chains can often be attributed to photochemical reactions arising from the absorption of UV radiation by polymeric chromophores. A number of carbonyl species including aliphatic type ketones, monomer, alcohols, and esters, as well as a drop in molecular weight resulting from the photodegradation, have been identified on the bases of experimental results [17–20], but as yet, there is no general agreement on the nature of the products resulting from photodegradation of
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