The contact charge transfer (CCT) complex can be formed between poly(propylene oxide)(PPO) as an electron donor and oxygen as an electron acceptor.A reversible CCT absorption appears at 226 4nm due to their very weak combination.The result shows that without initiator and in the dark

the oxidation of PPO goes through the initial state of O2 CCT as same as the oxidation of its model compound isopropyl ether.It is proposed that the initial dark oxidation of PPO undergoes through O2 CCT

CTC

H + transfer

free radicals in cage

and the formation of hydroperoxide.The hydroperxide is the primary product of dank oxidation and its subsequent decomposition results in the chain cleavage with decrease of the molecular weight of PPO.