Study of the crystalline structures of the syndiotactic polystyrene (sPS) under mechanical deformation

Polystyrene (PS) has become one of the important, yet complicated semi-crystalline materials since the successful synthesis of the syndiotactic PS (sPS) by Ziegler-Natta catalyst. Since then, sPS has been actively investigated and four different crystalline forms ($\alpha $, $\beta $, $\gamma $ and $\delta )$, two mesomorphic forms and various clathrate forms have been found, indicating complex feature of its crystalline structures. Among the four crystalline forms, $\alpha $ and $\beta $-crystals can be obtained by different annealing processes and both crystalline structures comprise the same all-trans planar conformation. In this work, $\beta $-crystal structure was made by high temperature annealing and the sPS with $\beta $-crystal structure was mechanically stretched above the glass transition temperature of sPS, followed by the crystalline transition analysis studied by FT-IR.