Enthalpy of fusion of poly(3-hexylthiophene) by differential scanning calorimetry

ABSTRACT The enthalpy of fusion for a perfect, infinite poly(3‐hexylthiophene) (P3HT) crystal (ΔHm∞) must be known to evaluate the absolute crystallinity of P3HT. This value, however, is still ambiguous as different values have been reported using various experimental techniques. Here, we extrapolate the enthalpy of fusion for extended chain crystals of oligomeric P3HT to infinite molecular weight and obtain a value of ΔHm∞≈ 42.9 ± 2 J/g employing differential scanning calorimetry with a correction based on grazing incidence small angle X‐ray scattering data. Also, we define the onset of chain folding within P3HT crystallites at a chain length of 5 Kuhn segments. Knowledge of ΔHm∞ allows calculation of P3HT percent crystallinity in thin films for applications such as organic field effect transistors and solar cells. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 1469–1475 Knowledge of the enthalpy of fusion for poly(3‐hexylthiophene) is important to determine its crystallinity after it is deposited or processed. Differential scanning calorimetry (DSC) of low molecular weight samples is demonstrated to be an effective technique to obtain it. Grazing incidence small angle scattering was employed to find a correction factor for the samples' amorphous content near the crystal edge and applied to the DSC data to improve the accuracy of the result, 42.9 ± 2.0 J/g.