The relation between phase transition and crystallization behavior of 1,4‐trans‐poly(butadiene)

The crystallization behaviour of pure 1,4‐trans‐poly(butadiene) (1,4‐PTBD) from dilute solutions in heptane and its relation to the phase transition phenomena in the solid state is investigated. Depending on whether the nucleation occurs in the high‐temperature modification II or the low‐temperature modification I two different regimes of crystallization behaviour are observed which in turn determine the crystal thickness as well as the phase transition and annealing behaviour of the crystals. The equilibrium phase transition temperature (I–II) is 356 K, the corresponding enthalpy is 144 J.g−1; the equilibrium melting temperature is 437 K and the enthalpy of melting is 69 J.g−1. The surface free energy terms are obtained relating the crystal thicknesses measured by SAXS and DSC to the temperatures of phase transition and melting, resp. Following Hoffman's theory of nucleation and growth the theoretical curves for the rate of nucleation and crystal growth are calculated and compared to the experimental results.