Effect of cosolvent on solid phase transitions of α‐ to β‐form crystal of syndiotactic polystyrene occurred in supercritical Co2 containing solvent |
| |
Authors: | Xia Liao Jiasong He Jun Zhang Weiming Ma |
| |
Affiliation: | 1. Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory of Engineering Plastics, Joint Laboratoryof Polymer Science and Materials, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, China;2. Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory of Engineering Plastics, Joint Laboratoryof Polymer Science and Materials, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, ChinaBeijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory of Engineering Plastics, Joint Laboratoryof Polymer Science and Materials, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, China |
| |
Abstract: | The solid phase transition mechanism of α‐ to β‐form crystal upon specific treating with supercritical CO2 + cosolvent on original pure α and mixed (α+β) form syndiotactic polystyrene (sPS) was investigated, using wide angle X‐ray diffraction and differential scanning calorimetry measurements as a function of temperature, pressure, and cosolvent content. As in the supercritical CO2, sPS in supercritical CO2 + cosolvent underwent solid phase transitions from α‐ to β‐form, and higher temperature or higher pressure favored this transformation. Due to the higher dipole moment of acetone, small amounts of acetone used as cosolvent with CO2 made the transition of α‐ to β‐form occur at lower temperature and pressure than in supercritical CO2, and made the α‐form crystal completely transform to β‐form in the original mixed (α+β) form, whereas ethanol did not. The original β‐form crystal in the original mixed (α+β) form sample acted as the nucleus of new β‐form crystal in the presence of cosolvent as it did in supercritical CO2, when compared with the original pure α‐form sample. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1625–1636, 2007 |
| |
Keywords: | cosolvent polymorphism polystyrene solid phase transition supercritical CO2 syndiotactic polystyrene transitions |
|
|