Interchain electron states in polyethylene

We present a theoretical study of the nature of the lowest empty conduction-band stairs in crystalline polyethylene (PE), conducted through density-functional electronic structure calculations. Results reveal that the wave function of the conduction-band edge is of interchain character, as opposed to the intrachain character of all the filled valence-band states. Thus, while a hole added to neutral PE will mainly belong to the PE chain backbone bonds, an added electron in PE will mostly reside between the chains, and far from the existing bonds. Moreover, the added electron state charge centroid is predicted to move further out from the chain backbone towards the low-density interstitial region, if and when the chains are pried apart. This suggests that injected electrons will naturally flow to low-density regions inside real PE, and that the experimentally established propensity of PE to expel electrons out of the bulk, should be directly related to the interchain nature of the conduction states.