Miscible blends of syndiotactic polystyrene and atactic polystyrene. Part 2. Depolarized light scattering studies and crystal growth rates

Chi Wang, Wei Po Liao, Ming Ling Wang, Chang Chun Lin

研究成果: Article同行評審

17 引文 斯高帕斯(Scopus)

摘要

Crystallization kinetics and morphology in miscible blends of syndiotactic polystyrene (sPS) and atactic postyrene (aPS) have been investigated by means of time-resolved depolarized light scattering (DPLS), polarized optical microscopy (POM) and scanning electron microscopy (SEM). Two different weight-average molecular weight of aPS, i.e. Mw=100k and 4.3k, were used to prepare the blends and denoted sPS/aPS(H) and sPS/aPS(M), respectively. Owing to a dilution effect, addition of aPS reduces the crystal growth rate and the overall crystallization rate of sPS; the reduction is more significant in sPS/aPS(M) of which a depression of equilibrium melting temperature is found due to the enhanced mixing entropy. Linear crystal growth is always observed in sPS/aPS(H) at the temperatures studied (240-269°C) and results in an interfibrillar segregation morphology revealed by SEM, whereas sPS/aPS(M) with high aPS content exhibits non-linear growth behavior at low supercooling and gives an interspherulitic segregation morphology. Based on the Lauritzen-Hoffman theory, the fold surface free energies (σe) of sPS lamellae derived from DPLS and POM are in fair agreement, being 15.1erg/cm2 from the former and 12.6erg/cm2 from the latter. The peculiarly low values of σe and the derived work of chain folding are discussed briefly. On addition of aPS, the lateral surface free energy of lamellae remains intact (9.9erg/cm2) regardless of aPS molecular weight used, which is ascribed to the absence of specific interaction between sPS and aPS components. Moreover, it seems that the activation energy for sPS chains to diffuse from the miscible melt to the crystal growth front is slightly increased in sPS/aPS(M), plausibly attributable to the extra energy required for the demixing process.

原文English
頁(從 - 到)973-981
頁數9
期刊polymer
45
發行號3
DOIs
出版狀態Published - 2004 2月

All Science Journal Classification (ASJC) codes

  • 有機化學
  • 聚合物和塑料
  • 材料化學

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