AN IN-SITU SAXS WAXS/RAMAN SPECTROSCOPY STUDY ON THE PHASE-BEHAVIOR OF SYNDIOTACTIC POLYSTYRENE (SPS)/SOLVENT SYSTEMS - COMPOUND FORMATION AND SOLVENT (DIS)ORDERING/

In situ small-and nide-angle X-ray scattering (SAXS and WAXS) experime nts combined with Raman spectroscopy and thermal analysis have been pe rformed to study the phase behavior of syndiotactic polystyrene (sPS) solutions. Three different solvents were used, respectively, decalin, benzyl methacrylate, and cyclohexyl methacrylate. When sPS solutions a re quenched, gel formation occurs. In these gels sPS adopts a helical conformation that is stabilized by the solvent molecules; in fact, com pound formation occurs. From the combined experimental data it was con cluded that two different structural modifications exist within the so lvent-included helical delta-phase, respectively the delta'-phase, in which the solvent molecules are intercalated and ordered between the p henyl rings of sPS, and a delta''-phase, where the solvent ordering is lost. The so-called gamma-phase, the solvent-free helical phase, was not observed in our studies. The transformation from the helical (delt a'') phase to the planar zigzag (beta) phase occurs via melting and re crystallization. Under specific conditions, the beta-phase is metastab le, even in its thermodynamically stable region.