Conformational transitions and aggregations of regioregular polyalkylthiophenes

Diverse conformational transitions and aggregations of regioregular poly (3-alkylthiophene)s (PATs) in different environment have been studied by means of AFM and UV-vis-spectroscopy. In methanol, which is a non-solvent for both alkyl side groups and aromatic backbone at low polymer concentration, PATs chains fold into compact poorly ordered flat structures. At higher polymer concentration PATs molecules undergo 3D aggregation into near spherical particles. In hexane, which is a selective solvent for alkyl side chains, PATs molecules undergo ordered main-chain collapse followed by 1D aggregation. Concentration-independent red shift of λmax and good resolved fine vibronic structure in the electronic absorption spectra indicate that planarization occurs on the single-molecule level.