Towards a theoretical design of thermochromic polythiophenes

Ab initio calculations have been performed on several bithiophene derivatives which are the building blocks of substituted polythiophenes in order to correlate their torsional potential energy curves with the thermochromic properties of the parent polymers. It is found that the occurrence of thermochromism in polythiophenes can be related to the values of the energy barrier calculated for the dimer models. Moreover, trends in the thermally induced blue-shift observed with some polythiophene derivatives can be related to the difference in the torsional angles between a co-planar conformation and the more stable conformation of the corresponding bithiophene moieties.