Abstract
By means of simultaneous small/wide-angle X-ray scattering and differential scanning calorimetry (SAXS/WAXS/DSC) measurements, a new experimental approach in constructing the Gibbs-Thomson melting line for determination of equilibrium melting temperature (Tmº) and fold surface energy (σe) in melting line is proposed recently by Su et al. for the specific case of syndiotactic polystyrene (sPS). This approach adopts Kratky-Porod approximation and one-dimension correlation in analyzing the lamellar thickness from synchrotron radiation SAXS data. Here we proposed to check the general reliability of such an approach by its application to extensively studied polymers of known Tmº and σe values in melting line, including polyethylene (PE, Tmº = 145.5 ºC and σe = 40 to 100 mJ m–2) and poly(ethylene oxide) (PEO, Tmº = 68.9 ± 0.4 ºC and σe = 23 to 93 mJ m–2). Moreover, a new method of arrayed-disks model is adopted in this work successfully. The equilibrium melting temperatures (via extrapolation of the melting line to infinite lamellar thickness) are determined as Tmº = 145.1 ± 2.3 ºC for polyethylene and Tmº = 70.2 ± 0.5 ºC for PEO. Meanwhile, we estimate from the slope of the melting line that the fold surface energies are σe = 89.7 ± 8.9 mJ m–2 for PE and σe = 23.8 ± 4.5 mJ m–2 for PEO. The experimental results are consistent with the currently known values, indicating that the method we adopted to construct the melting line is feasible and of improved confidence level (especially for σe in the equilibrium limit).