Mid-infrared spectroscopic investigation of the perfect vitrification of poly(ethylene glycol) aqueous solutions.
Mid-infrared spectroscopic investigation of the perfect vitrification of poly(ethylene glycol) aqueous solutions.
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DOI：
10.1021/acs.langmuir.5b02829
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发表时间：
2015-09
期刊：
影响因子：
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通讯作者：
Makoto Gemmei-Ide;T. Miyashita;S. Kagaya;H. Kitano
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文献类型：
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作者：
Makoto Gemmei-Ide;T. Miyashita;S. Kagaya;H. Kitano
采用变温中红外光谱法研究了聚乙二醇（PEG）水溶液的结晶/重结晶行为。在43.2wt%的WC下，没有观察到水和PEG的结晶和重结晶。在此特定WC值（WCPV）下，发生完全玻璃化。低于和高于WCPV值，结晶/再结晶行为发生剧烈变化。低于WCPV时的晶化温度（237 K）比高于WCPV时的晶化温度（226 K）高约10 K。高于和低于WCPV的重结晶分别发生在一个（213 K）和两个（198和210 K）步骤。这些发现是由于与具有螺旋和无规卷曲构象的PEG链相关的水分子的（重）结晶行为的差异造成的。这两种类型的水分子可能具有其（再）结晶的极限浓度，这表明当这两种类型的水分子的浓度小于其（再）结晶的极限浓度时，可能已经发生了完美的玻璃化。
Crystallization/recrystallization behaviors of poly(ethylene glycol) (PEG) aqueous solutions with water contents (WC's) of ∼36-51 wt % were investigated by temperature-variable mid-infrared spectroscopy. At a WC of 43.2 wt %, crystallization and recrystallization of water and PEG were not observed. At this specific WC value (WCPV), perfect vitrification occurred. Below and above the WCPV value, crystallization/recrystallization behaviors changed drastically. The crystallization temperature below WCPV (237 K) was ∼10 K greater than that above WCPV (226 K). Recrystallization above and below WCPV occurred in one (213 K) and two (198 and 210 K) steps, respectively. These findings resulted from the difference in the (re)crystallization behaviors of water molecules associated with PEG chains with helical and random-coil conformations. These two types of water molecules might have limiting concentrations for their (re)crystallization, indicating that perfect vitrification might have occurred when the concentrations of the two types of water molecules were less than the limiting concentrations of their (re)crystallization.