On the modeling of aggregates of an optically active regioregular polythiophene

The conformational properties of the optically active regioregular poly[(R)-3-(4-(4-ethyl-2-oxazolin-2-yl) phenyl) thiophene] (PEOPT) were explored by molecular dynamics on a single chain using several solvents of increasing polarity. Furthermore, their aggregate formation was studied over a wide range of temperatures using a replica exchange molecular dynamics simulation providing simulation data representative of the equilibrium behaviour of their aggregates. Results show a clear tendency of PEOPT to keep a syn-gauche conformation between continuous backbone thiophene rings favouring a bent chain structure in solvent. After studying their aggregation behaviour in acetonitrile, a strong tendency to pack stabilizing structures that reinforce the chirality of the polymer, in concordance with experimental data, was found. Two different aggregated structures were observed depending on oligomer length, a self-assembled helical aggregate based on stacked octamers and a bent double helix aggregate in large oligomers.