Abstract
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.
Highlights
IntroductionAs a high stereoregularity polymer, syndiotactic polystyrene (sPS) has attracted long-standing interest because of its high melting point, fast crystallization rate, and good chemical stability [1]
As a high stereoregularity polymer, syndiotactic polystyrene has attracted long-standing interest because of its high melting point, fast crystallization rate, and good chemical stability [1].The polymorphic behaviors related to different molecular conformations and different chain packing structures have been extensively studied over the years [2,3,4,5,6,7,8]
The gel melting process during heating can be stated as a dissociation process of helical aggregates at low temperature—in this case, NP molecules still combined with helical chains
Summary
As a high stereoregularity polymer, syndiotactic polystyrene (sPS) has attracted long-standing interest because of its high melting point, fast crystallization rate, and good chemical stability [1]. Fluorescence anisotropy has been applied in sPS and iPS gels to determine the free volume in thermo-reversible gels or in polymer host nanoporous films to monitor the orientation of guest molecules by incorporating sizeable dye molecules (e.g., naphthalene) into the polymer–solvent system or into sPS nanoporous films [20,38,39,40,41,42]. The relaxation behavior of sPS chains at various temperatures has not been considered using the fluorescence anisotropy technique. In order to obtain specific mechanisms and dynamics of structural relaxation behavior of sPS gels, the present work investigates the progressive relaxation of chains in the gel melting process by intrinsic fluorescence and fluorescence anisotropy techniques
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