Cumene and other derivatives of benzene can form reversible contact charge transfer complexes (CCT) with O2

but due to the influence of the space structure of polystyrene (PS) such as steric or electronic effect caused by the neighboring benzene ring

the O2 CCT of PS is irreversible. High molecular weight PS(HPS) gives its maximum absorption wavelength of O2 CCT at 278.4nm

but low molecular weight PS(LPS) at 295.6nm as it has a similar structure of styrene due to a double bond at one end of its chain which results in the red shift of O2-CCT absorption.The CCT formed between PS and O2 has been considered as the initial state of the dark oxidation and it is proposed that PS as like the model compound cumene undergoes dark oxidation through O2-CCT

CTC

H+transfer

free radicals in cage and the formation of hydroperoxides.