First detailed determination of the molecular conformation and the crystalline packing of a chiral poly(3-alkylthiophene): Poly-3-(S)-2-methylbutylthiophene

The process of detailed refinement of the crystal structure of chiral poly-3-(S)-2-methylbutylthiophene (PMBT) was analyzed. The high regioregularity, the small side chain dimension, and the substantial crystallinity of PMBT, was estimated by comparison with patterns of fully amorphous samples. A good agreement was observed between calculated and observed XRD patterns that confirms the adopted simplifying assumptions and suggests that it is necessary for the PMBT crystal structure to invoke complex disorder models. By integration of the calculated crystalline and amorphous pattern resulting from the refinement, a crystallinity of 65 ±5% is obtained. Exploration by molecular dynamics of aggregation process of polythiophenes helps in the simplicity of the refined structural model. It was also observed that the likelihood of different chiral aggregate models may depend on morphology.