SIMULTANEOUS SAXS AND LIGHT SCATTERING MEASUREMENTS OF POLYMER CRYSTALLIZATION AND PHASE TRANSITIONS Richard S. Stein and Yvonne Akpalu, University of Massachusetts; H. G. Zachmann, J. Cronauer, and S. Groth, University of Hamburg, Germany

Simultaneous small-angle x-ray (SAXS) and light scattering (SALS) and wide-angle x-ray diffraction (WAXD) measurements were made during the melting and crystallization of blends of linear and branched polyethylene.

The degrees of crystallinity were obtained from the WAXD, the invariants and identity periods from the SAXS, and the spherulite sizes and light scattering invariants from the SALS using Hv and Vv polarization. The Vv SALS invariant exhibited a maximum when samples were about half filled with spherulites, whereas the Hv invariant monotonically increased. The SALS intensity continued to increase after the spherulites became volume filling demonstrating secondary crystallization within previously formed spherulites. The identity period decreased in latter stages of crystallization as the branched component crystallized.

Measurements were made during one-stage crystallization as well as during two-stage, where in the first stage, the temperature was first held below the melting point of the linear component but above that of the branched, and then in the second stage, it was held below the melting points of both. While differences were observed during crystallization for miscible and immiscible melts, the striking difference occurred during melting, where a scattering maximum occurred for the immiscibile melt but not for the miscible.