Dynamics of Uncrystallized Water, Ice, and Hydrated Polymer in Partially Crystallized Poly(vinylpyrrolidone)-Water Mixtures
Dynamics of Uncrystallized Water, Ice, and Hydrated Polymer in Partially Crystallized Poly(vinylpyrrolidone)-Water Mixtures
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部分结晶聚（乙烯基吡咯烷酮）-水混合物中未结晶水、冰和水合聚合物的动力学
DOI：
10.1021/acs.jpcb.9b11552
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Yagihara Shin
中科院分区：
文献类型：
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作者：
Fujii Mitsuki;Sasaki Kaito;Matsui Yurika;Inoue Shiori;Kita Rio;Shinyashiki Naoki;Yagihara Shin
在这项研究中，我们研究了合作的分子动力学的聚（乙烯吡咯烷酮）（PVP），冰，和未结晶水（UCW）在部分结晶PVP-水的混合物通过宽带介电谱。三个弛豫过程，表示为I，II和III，观察到的温度范围从立即低于结晶温度（Tc）约200 K。在173-193 K的温度下，过程I和II不能区分。在168 K以下，过程II分为两个过程：过程IV在较高频率下，过程V在较低频率下。过程I有助于过程V。在部分结晶的混合物中，过程I源自与PVP处于非结晶相的UCW。过程II归因于混合物中的冰，具有比纯冰小2个数量级的弛豫时间。过程II的强度和相对于冰在牛血清白蛋白（BSA）-水和明胶-水的混合物的弛豫时间的浓度依赖性强烈支持这一结论。过程IV和V的观察表明存在多个冰松弛过程。过程III归因于40和50 wt % PVP混合物中未结晶相中PVP的α过程。对于含30wt%PVP或更少的混合物，过程III不仅归因于PVP的α过程，而且归因于界面极化。
In this study, we investigated the cooperative molecular dynamics of poly(vinylpyrrolidone) (PVP), ice, and uncrystallized water (UCW) in partially crystallized PVP–water mixtures by means of broadband dielectric spectroscopy. Three relaxation processes, denoted I, II, and III, were observed at temperatures ranging from immediately below the crystallization temperature (Tc) to approximately 200 K. At temperatures of 173–193 K, processes I and II cannot be distinguished. Below 168 K, process II separates into two processes: process IV at higher frequencies and process V at lower frequencies. Process I contributes to process V. In partially crystallized mixtures, process I originates from UCW in an uncrystallized phase with PVP. Process II is attributed to ice in the mixture, with a relaxation time that is 2 orders of magnitude smaller than that of pure ice. The concentration dependence of the strength of process II and the relaxation time relative to that of ice in bovine serum albumin (BSA)–water and gelatin–water mixtures strongly support this conclusion. Observation of processes IV and V indicates the presence of multiple ice relaxation processes. Process III is attributed to the α process of PVP in the uncrystallized phase in 40 and 50 wt % PVP mixtures. For mixtures with 30 wt % PVP or less, process III is attributed not only to the α process of PVP but also to interfacial polarization.