Free volume changes, crystallization, and crystal transition behavior of syndiotactic polystyrene in supercritical CO2 revealed by positron annihilation lifetime spectroscopy

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The free volume of syndiotactic polystyrene (sPS) conditioned in supercritical CO2 was investigated by using positron annihilation lifetime spectroscopy (PALS). Supercritical CO2 increased the free volume cavity size of amorphous sPS and made the formation of gamma crystal occur. The orthopositronium (o-Ps) intensity I-3 was correlated well with the crystallinity of gamma form sPS, revealed by its gradual decrease with the increase of crystallinity. Furthermore, the treatment atmosphere affected the crystallization behavior of amorphous sPS. The increased free volume cavity size of amorphous sPS treated in supercritical CO2 was larger than those treated in ambient air and supercritical N-2. Among these treatment conditions, supercritical CO2 increased the free volume size of amorphous sPS more effectively and thus resulted in the formation of gamma crystals. PALS measurements indicated that supercritical CO2 helped remaining a constant high free volume level of the amorphous parts of the semicrystalline sPS. Likely, the crystalline parts were also affected by the scCO(2) as a transition from the gamma form to the beta form was revealed at high temperatures by WAXD.


  • Weiming Ma
  • Anna Andersson
  • Jiasong He
  • Frans Maurer
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Chemical Sciences
Original languageEnglish
Pages (from-to)5307-5312
Issue number14
Publication statusPublished - 2008
Publication categoryResearch

Bibliographic note

The information about affiliations in this record was updated in December 2015. The record was previously connected to the following departments: Polymer and Materials Chemistry (LTH) (011001041)