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On the multiple melting behavior of polymorphic syndiotactic polystyrene and its behavior in a miscible state
Author(s) -
Woo E. M.,
Wu Fu Sun
Publication year - 1998
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/(sici)1521-3935(19980901)199:9<2041::aid-macp2041>3.0.co;2-2
Subject(s) - polystyrene , differential scanning calorimetry , tacticity , annealing (glass) , amorphous solid , materials science , crystallization , polymer chemistry , melting point , glass transition , phenylene , polymer blend , melting temperature , analytical chemistry (journal) , chemical engineering , crystallography , polymer , chemistry , polymerization , copolymer , composite material , thermodynamics , organic chemistry , physics , engineering
Differential scanning calorimetry (DSC) and X‐ray diffraction analysis were performed to study the multiple melting behavior and crystal forms of neat syndiotactic polystyrene (s‐PS) in comparison with its miscible blends with amorphous atactic polystyrene (a‐PS) or poly(2,6‐dimethyl‐ p ‐phenylene oxide) (PPO). For neat s‐PS annealed at 242 to 250°C, three melting peaks of changing intensity were observed (labeled I, II, and III from low to high temperature), while if annealed at high temperatures (254°C or higher) only two melting peaks were left. The missing peak was determined to be Peak‐III for s‐PS annealed at high temperatures. For the s‐PS/a‐PS or s‐PS/PPO blends, two melting peaks were observed, and the missing peak is Peak‐II. The missing Peak‐II in the blend systems is attributed to the β‐modification. Apparently, the condition of s‐PS being compatible with a‐PS or PPO is unfavorable for generating the β‐modification upon melt crystallization. This study also showed that Peak‐I is associated with the β‐modification. Peak‐III may be associated with the less stable β′ form, which can be transformed to the β form upon annealing at high temperatures. For the s‐PS/a‐PS or s‐PS/PPO blends upon annealing at higher temperatures, Peak‐III quickly decreases, leaving only a single melting peak (Peak‐I) for the blends. The phenomenon of the decrease of Peak‐III crystals in the blend is similar to that for neat s‐PS annealed at high temperatures.