THE RADIATION CHEMISTRY OF SQUALENE

Squalene was irradiated with Co60 γ-rays at room temperature and with 1-MeV electrons at −30 °C. The main radiation-induced effects, and their G-values for the room temperature irradiations, were loss of unsaturation (4.6), crosslinking (1.35), trans → cis isomerization (0.83), and evolution of hydrogen (0.58). The G-values for the first three processes in the low temperature runs were 3.8, 0.82, and 0.83, respectively. The large drop in unsaturation is attributed in part to the formation of crosslinks involving double bonds, but principally to cyclization. The loss of double bonds occurs only in the immediate vicinity of the crosslinks and not at random throughout the irradiated squalene. This result has important implications for the radiolysis of diene polymers. Squalene in 10% benzene solution isomerizes with a much higher yield (apparent G-value of 2.6 trans double bonds converted initially per 100 eV absorbed by both solute and solvent) than that of the pure olefin, indicating very efficient energy transfer from excited benzene molecules to the squalene double bonds. The isomerization in the solution case was accompanied by a loss of double bonds in squalene (G-value of 0.98) due to phenylation as well as to the other indicated saturation reactions.