Time-Evolution of Polymer Spherulite Formation Investigated by Light Scattering.

The time-evolution of polymer spherulite formation in the melt was investigated by H_v light scattering. The H_v scattering gives both the 'four-leaf clover pattern' and isotropic scattering independent of azimuthal angle. The isotropic scattering from spherulites of isotactic polystyrene is measured over a wide range of crystallization: from bundles to a matured spherulite. Correlation length is obtained from the isotropic scattering. In the early stage of spherulite growth, the correlation length increases in proportion to crystallization time and reaches maximum value of about 1 µm. Hence, the isotropic scattering is attributed to the bundles. The correlation length is the size of the bundles. The bundles grow and successively evolve to spherulites by branching. In the late stage, a matured spherulite grows. However, the correlation length decreases to a value of about 0.6 µm and remains unchanged. By re-examination of the lattice model of Yoon and Stein, the model is found applicable to matured spherulites. The correlation length in matured spherulites is suggested to be the distance between branches of a bundle. The length agrees to a distance between screw dislocations in a crystal grown from the polymer melt. [ABSTRACT FROM AUTHOR]