The thermoreversible gelation of syndiotactic polystyrene

Progressive Relaxation Behavior and Relaxation Dynamics of sPS Gels upon Controlled Heating

Progressive relaxation behavior of syndiotactic polystyrene (sPS) chains in sPS gel was detected in the course of melting via the application of intrinsic fluorescence and fluorescence anisotropy techniques. The melting process included a dissociative process of the network at lower temperature and a relaxation process from helix to worm-like chains at higher temperature. The dynamics of structural relaxation behavior was discovered by intrinsic fluorescence technique, and an abrupt bend emerged at 58 °C on the Arrhenius plot. At temperatures lower than 58 °C, only the dissociation of the helical structure existed and the rate of relaxation from helix to worm-like conformation was negligible. At temperatures higher than 58 °C, the transition from helical chain to worm-like chain was the rate-determining step. The intrinsic fluorescence technique demonstrated its practicability in detecting kinetic processes of sPS/chloroform gel in the course of melting.

Phase behaviour and structure formation in solutions of vinyl polymers

The supramolecular structure formation in solutions of syndiotactic polystyrene is discussed from the viewpoint of the temperature-concentration behaviour of this system. The phase diagrams that result from these investigations localize the different temperature-concentration domains in which the β -phase (planar zigzag chain conformation) and the δ -phase (helix chain conformation) are formed. The study of these diagrams informs also on the relationship between the different phases and the nature of the supramolecular structure that is formed. The shape of the diagrams is characteristic of the formation of an incongruent melting compound ( δ -phase) between the polymer and the solvent. The formation of this compound at not to high polymer concentrations leads to the formation of thermoreversible gels. The solvent quality has a different influence on the stability of the β - and the ( δ -phase. An increase of the solvent quality lowers the melting point of the β -phase, but increases the stability of the ( δ -phase. The diagrams are interpreted on the basis of schematized equilibrium diagrams.