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 mol ecular dynamics. The single chains and clusters consisting of two mole cules in full atomic representation were considered. Three types of st able conformers of the single polypropyl-3-thiophene molecule were fou nd in poor solvent conditions. One type of conformer was revealed for polyhexadecyl-3-thiophene. It was shown that the tendency to intramole cular aggregation in poor solvent conditions is much more pronounced f or polythiophenes (PTs) with shea substituents. The cluster of PT deri vatives was shown to be very stable in poor solvent conditions. The di stribution of dihedral angles along the backbone was determined to be much narrower for both intra- and intermolecular aggregates in poor so lvent than for single molecules in good solvent. The calculated distri bution was related to changes in the absorption spectrum in the solvat ochromic transition. The agreement between calculated and experimental ly observed solvatochromic changes of the absorption spectrum supports the expectation that PTs with short substituents may form the intramo lecular aggregates with revealed structure. (C) 1998 Elsevier Science S.A. All rights reserved.