Molecular mechanics study of the influence of the alkyl substituents on the packing of the conjugated PEDOT chains

The solid state packing of neutral chains of the conjugated polymers is studied by theoretical simulations. The conjugated systems considered here are the pol(3,4-ethylenedioxythiophene (PEDOT) and their substituted PEDOT derivatives PEDOT-C10H21. The molecular mechanics calculations indicate that the polymers tend to form stable π stacks and indicate that the alkyl side groups freeze the conjugated segments and allow a good organization of PEDOT-C10H21 chains. This explains the increase of conductivity in these systems compared to un-substituted PEDOT. Finally, the introduction of one defect in region-regularity causes a steric hindrance, resulting in less order and less compact π-stacking.