Characteristics of several kinds of polyethylene gel estimated by small-angle light scattering under cross polarization

Abstract

Unusual phenomenon was confirmed in the gelation of polymer solution when branched low molecular weight polyethylene (B-LMWPE) and ultrahigh molecular weight polyethylene (UHMWPE) solutions were quenched at their gelation temperature. That is, polarized light scattering (Hv scattering) from B-LMWPE gels containing 95% solvent yielded a four-leaf clover type as like the scattering from a perfect spherulite under Hv scattering but the corresponding polarized optical microscopy (POM) showed dark image showing no spherulite with Maltese cross color indicating considerable orientation fluctuation between the optical axes with respect to the radial axis of the spherulite. Hv scattering from pristine UHMWPE gels containing more than 99% solvent had an X-type pattern, which became clearer with time. The corresponding POM images change from being dark, indicating no superstructure, to being slightly brighter, indicating the presence of indistinct superstructures. To analyze this unusual phenomenon of Hv scattering from B-LMWPE and UHMWPE gels, new models were proposed using a statistical approach and optically anisotropic elements in three-dimensional space. The theoretical patterns were in agreement with observation. Thus, it came to a conclusion that Hv scattering from the gels is attributed to strong distance correlation between polar and rotational angles of two optically anisotropic elements in the polymer-rich phase. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010