Morphology and thermodynamic properties of solution‐grown single crystals of trans‐1,4‐polybutadiene

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Abstract
The morphology and thermal behavior of trans‐1,4‐polybutadiene single crystals prepared from dilute 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 we find a value of 75°C for the equilibrium transition temperature between forms 1 and 2, 139°C for the equilibrium melting temperature of form 2, and 31.2 erg/cm2 for the fold‐surface free energy of modification 2.