Gibbs-Thomson analysis of crystalline poly(9,9-di-n-octyl-2,7-fluorene)

Based on results of small-angle X-ray scattering and differential scanning calorimetric measurements, the equilibrium melting temperature and basal surface energy (sigma(e)) of crystalline poly(9,9-di-n-octyl-2,7-fluorene) (PFO) were preliminarily estimated as ca 451.6 K and 0.084 J m(-2), respectively, via Gibbs Thomson analysis. This sigma(e) value leads to a value of 76 kJ mol(-1) for the work of fold that greatly exceeds the values for typical polymers, reflecting the semi-rigid nature of the PFO backbone and consistent with the large-loop folds proposed earlier for this particular conjugated-backbone polymer. This is in strong contrast to the commonly held belief that conjugated polymers are generally too rigid to form folded-chain lamellar crystals.