Journal of Polymer Science Part B: Polymer Physics, 2018, vol 56, 3, pp. 219-224
DOI:10.1002/polb.24536
Abstract
The isothermal crystallization and subsequent melting process in semicrystalline poly(4-methyl-1-pentene) were investigated via temperature-dependent small- and wide-angle X-ray scattering and Flash DSC techniques. In a phase diagram of inversed crystalline lamellar thickness and temperature, the crystallization and melting lines can be described by two linear dependencies of different slopes and different limiting temperatures at infinite lamellar thickness. Upon subsequent heating, recrystallization lines with different slopes were observed for samples with different lamellar thickness, indicating changes in surface free energy difference between stabilized crystallites and mesomorphic phase. The surface free energy of native crystallites with extended-chain conformation decreased with increasing lamellar thickness due to a more ordered surface region and less chain ends which changes cooperatively with mesomorphic phase. The surface free energy of stabilized crystallites remained unchanged for all lamellar thickness. Therefore, the recrystallization lines with different slopes are consequences of changes in surface free energy of mesomorphic phase. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 219–224
