MORPHOLOGY AND THERMODYNAMIC PROPERTIES OF SOLUTION-GROWN SINGLE-CRYSTALS OF TRANS-1,4-POLYBUTADIENE

In the reported experiments, the morphology and thermal behavior of trans-1,4-polybutadiene single crystals prepared from silute solutions in n-heptane have been investigated by electron microscopy, wide-angle and low-angle x-ray diffraction, and differential scanning calorimetry. The thickness of the single crystals of trans-1,4-PBD is much greater, for the same undercooling, than that of other linear polymers. From the calorimetric study, convincing evidence of the presence, in the single crystals, of crystalline blocks of form 1 with two different thermodynamic stabilities is obtained and the relative amounts are calculated. From thermodynamic considerations, the following values were obtained: 75 degree C for the equilibrium transition temperature between forms 1 and 2, 139 degree C for the equilibrium melting temperature of form 2, and 31. 2 erg/cm**2 for the fold-surface free energy of modification 2.