MOLECULAR-STRUCTURE BY NEUTRON-SCATTERING OF THERMOREVERSIBLE GELS FROM CHEMICALLY-MODIFIED POLY(VINYL CHLORIDE)S

The molecular structure of thermoreversible gels made up of poly(vinyl chloride) (PVC) and chemically-modified PVCs in diethyl oxalate has b een investigated by small-angle neutron scattering: The chemical modif ication, which chiefly takes place in the less-stereoregular sequences , consists of replacing a few-chlorine atoms by either hydrogen or ben zothiolate groups. It is Shown that small modifications significantly alter the gel structure. At small q vectors the results are analyzed b y considering cross-section polydispersed fibers characterized by a di stribution function of the type w(r) similar to r(-1). Results at larg er q vectors, which yield a q(-2) behavior, indicate that the fibers a re no longer compact at short distances. This behavior is interpreted with a sheetlike structure, which is thought to arise from the formati on of a polymer-solvent complex. Fiber associations, which occurs esse ntially through the weak links, is accounted for by an interdigitation mechanism of the sheetlike structures. All the results on the differe nt samples are discussed In the light of the polymer-solvent complex a nd its sheetlike structure and the interdigitation mechanism.