Conformation of polythiophene derivatives in solution

The behaviour of regioregular polypropyl-3-thiophene and polyhexadecyl-3-thiophene in poor and good solution conditions was simulated by molecular dynamics. The single chains and clusters consisting of two molecules in full atomic representation were considered. Three types of stable conformers of the single polypropyl-3-thiophene molecule were found in poor solvent conditions. One type of conformer was revealed for polyhexadecyl-3-thiophene. It was shown that the tendency to intramolecular aggregation in poor solvent conditions is much more pronounced for polythiophenes (PTs) with shea substituents. The cluster of PT derivatives was shown to be very stable in poor solvent conditions. The distribution of dihedral angles along the backbone was determined to be much narrower for both intra- and intermolecular aggregates in poor solvent than for single molecules in good solvent. The calculated distribution was related to changes in the absorption spectrum in the solvatochromic transition. The agreement between calculated and experimentally observed solvatochromic changes of the absorption spectrum supports the expectation that PTs with short substituents may form the intramolecular aggregates with revealed structure. (C) 1998 Elsevier Science S.A. All rights reserved.