THE RADIATION CHEMISTRY OF STYRENE AND POLYSTYRENE

Polystyrene labeled with tritium, mostly on the alpha carbon, was irradiated in vacuum with x rays. The volatile radioactive products were counted and analyzed by gas-chromatographic techniques. G values (molecules formed per hundred electron volts absorbed) were obtained for tritiated products, based on energy absorbed only by the labeled monomer units in the polystyrene. These G values would apply to a polystyrene in which each styrene unit had a tritium atom in it. The G's were: G(T),.00047; G(CH/sub 3/T), .00018; G for a fraction volatile at dry ice temperature but not at liquid nitrogen temperature (DIV fraction),.00095; G for a fraction volatile at room temperature but not at dry ice temperature (DINV fraction),.006l. From the extrapolation of values of deuterium isotope effects, tritium isotope effect values were estimated. G(H)'s of.0022 and.0046 for ihe alpha hydrogen were thus obtained, and corresponded to G(H)'s of .010 and.020 for the overall yield. These values may be compared with published values of.045 and .078. By assuming mechanisms for ihe formation of the other products, it was possible to calculate G's for the products from in unlabeled polystyrene. These G's were: G(GH/sub 4/),.00036; G(DIV fraction),.00085 to.21, depending on the mode of formation; and G(DINV fraction),.006lmore » if none of the product remained in the polystyrene. If only one to ten percent of the DINV products were actually collected, the true G(DINV) would be.061 to.6l. The mininium G values obtained for the components of the DINV fraction (based on complete removal from the polymer) were: G(benzene), .0052; G(toluene),.00022; G(ethylbenzene and xylene), .00018; and G(styrene),.0006l. The benzene might arise from exchange with solvent benzene trapped in the polymer during purification. Products from the gamma irradiation of an unlabeled polystyrene (dose 10/sup 8/ roentgens) were determined by mass spectrometry and included hydrogen with a G of.041. The detection of a dimer of styrene (G(dimer collected) =.00002) suggested that a significant amount of monomer was formed in polystyrene irradiation. In dosimetric studies, the products formed in the irradiation of water saturated with benzene were investigated. The phenol produced was found to be accompanied by a material resembling it. It was shown that a benzene-water dosimeter could be based on the absorbance of the 345 m mu peak associated with the phenol-like material. Finally, the radiation-induced polymerization of styrene was studied viscometrically and by dilatometry. The polymerization of styrene exposed to x rays or gamma rays was found to be markedly reduced in the presence of small concentrations of scintillators. Anthracene, p-terphenyl, and diphenylhexatriene were used and had similar effects. Anthracene at a concentration of about one gram per liter reduced the radical yield in styrene by about half. It was demonstrated that the scintillators did not cause any appreciable reduction in thermal polymerization rates. Therefore the observed effects were not due to simple scavenging of styrene radicals. The results suggested that in an irradiated solution containing scintillator, styrene, and benzene, the styrene would be protected by the scintillator and could at the same time be sensitized by energy transfer from benzene to scintillator to styrene.« less