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

Ma, Weiming; Andersson, Anna LU ; He, Jiasong and Maurer, Frans LU (2008) In Macromolecules 41(14). p.5307-5312
Abstract
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... (More)
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. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Macromolecules
volume
41
issue
14
pages
5307 - 5312
publisher
The American Chemical Society
external identifiers
  • wos:000257665900032
  • scopus:48949102028
ISSN
0024-9297
DOI
10.1021/ma8009068
language
English
LU publication?
yes
id
74cc438d-448a-4dba-8938-bb5777d28fc6 (old id 1254644)
date added to LUP
2008-10-29 15:31:47
date last changed
2017-07-30 03:46:46
@article{74cc438d-448a-4dba-8938-bb5777d28fc6,
  abstract     = {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.},
  author       = {Ma, Weiming and Andersson, Anna and He, Jiasong and Maurer, Frans},
  issn         = {0024-9297},
  language     = {eng},
  number       = {14},
  pages        = {5307--5312},
  publisher    = {The American Chemical Society},
  series       = {Macromolecules},
  title        = {Free volume changes, crystallization, and crystal transition behavior of syndiotactic polystyrene in supercritical CO2 revealed by positron annihilation lifetime spectroscopy},
  url          = {http://dx.doi.org/10.1021/ma8009068},
  volume       = {41},
  year         = {2008},
}