Integrated Microdynamics Mechanism of the Thermal-Induced Phase Separation Behavior of Poly(vinyl methyl ether) Aqueous Solution
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- 作者：Bingjie Sun ; Hengjie Lai ; Peiyi Wu
- 刊名：Journal of Physical Chemistry B
- 出版年：2011
- 出版时间：February 17, 2011
- 年：2011
- 卷：115
- 期：6
- 页码：1335-1346
- 全文大小：1455K
- 年卷期：v.115,no.6(February 17, 2011)
- ISSN：1520-5207
文摘
The thermal behavior of a poly(vinyl methyl ether) (PVME) aqueous solution (30 wt %) during a heating-and-cooling cycle is studied using FTIR spectroscopy in combination with 2D correlation analysis. The FTIR spectral data of O鈭扝, CH3鈭扥, and C鈭扝 stretching vibration regions provide detailed changes of hydrophilic and hydrophobic groups of PVME. Hydrogen bonds between hydrophilic groups and water and hydration interactions between hydrophobic groups and water are confirmed to be completely reversible in the heating-and-cooling cycle. Two-dimensional correlation method helps us to understand the microdynamics mechanism of phase separation behavior of PVME 30 wt % aqueous solution. During the heating process, the initially hydrated CH3 groups start to dehydrate as the first action of phase separation, and the initially hydrated CH2 groups follow to start their dehydration; interestingly, water molecules leave CH2 groups very fast, and the whole dehydration process of CH2 groups finishes even earlier than that of CH3. After hydrophobic groups finish their dehydrations, hydrogen bonds between hydrophilic group and water start to dissociate. 1:2 adducts formed between PVME and water dissociate first and transfer to the 1:1 adducts, whereas with further heating, 1:1 adducts eventually dissociate and release free water and free CH3鈭扥. PCMW method is used as supplement to determine changing conditions of various chemical structures. During the phase separation, O鈭扝 hydrogen bond in 1:2 adduct is found to dissociate between 35.5 and 39 掳C in a style, whereas the 1:1 adduct (also considered as free water) increases between 35.5 and 39 掳C in a style. Moreover, dehydration conditions of hydrophobic groups are also found. Both of the dehydrated states CH3 and CH2 increase like .