We extend a recent comprehensive study of 3-hexylthiophene oligomers to high molar mass poly(3-hexylthiophene) (P3HT) fractions, such as those used in organic photovoltaic devices. Through a combination of differential scanning calorimetry (DSC) and 13C nuclear magnetic resonance spectroscopy (NMR), we were able to quantify the enthalpy and melting temperature of P3HT samples with molar masses ranging from 3.6 kg/mol to 62 kg/mol. Our results are consistent with the results of the oligomer work, but we demonstrate that higher molar mass samples are needed to fully capture the curvature in the Form I crystal melting temperature data and improve the enthalpy extrapolation. Significant changes in the extrapolated values for the enthalpy of fusion needed for quantification of crystallinity and equilibrium melting temperature result from this improvement.
Pub Type: Journals
calorimetry, crystallinity, local order, NMR, semiconducting polymers