Free radicals on photolysis and radiolysis of polystyrene

The e.p.r. method has been used to study the radical stages of low-temperature photolysis and radiolysis of polystyrene and to demonstrate the difference in them due to the photoconversion of the cyclohexadienyl radical. The authors have determined the quantum yield of the reaction of radical formation (ø ≅ 10⁻⁵) which weakly depends on the wavelength of the absorbed light at 230<λ<340 nm and the mean depth (l) at which radicals form (l≅9 ohms m for λ = 254 nm, i.e. in the region of inherent absorption of PS, and l ≅350 ohms m at λ≅300 nm). A shift is observed in the absorption band of polystyrene to the long-wave region owing to the secondary photoreactions of the cyclohexadienyl and peroxide radicals.