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An environmentally responsive polymeric network has been demonstrated for incorporating an inorganic salt hydrate phase change material (PCM). The unique feature of this material is the capability of a polymer gel to simultaneously provide shape stabilization of a liquid salt hydrate phase at a lower temperature, and to reversibly adjust its assembly strength in response to a temperature increase. This approach enables convenient control over the viscosity of the PCM gel system, allowing for filling and removal of the mixture in a liquid state but operation in the solid/gel regime. The system consists of polyvinyl alcohol (PVA) dissolved in lithium nitrate trihydrate (LNH), a high-latent-heat salt hydrate PCM. Dynamic light scattering (DLS) and viscometry studies indicate that in dilute solution, PVA chains are more expanded in LNH than in water. At a concentration of 15 wt% PVA, the PVA/LNH system unlike PVA aqueous solutions gels and exhibits a temperature-triggered gel-to-sol transition. Gelation is achieved only with PVA with the highest degree of hydrolysis (98%), with the gelation temperature of 20 ± 1 °C as measured by DLS and rheology. ATR-FTIR spectroscopy shows that the PVA gelation is enhanced due to dehydration of PVA chains in LNH, as compared to PVA aqueous solutions. Physically crosslinked PVA/LNH gels demonstrate highly repeatable and reproducible performance during ten cycles of LNH melting/freezing, as shown by differential scanning calorimetry (DSC). Taken together, these results confirm that PVA-based gels are promising matrices for hosting inorganic PCMs that withstand repeated melting/freezing cycling, but can be easily filled or drained as needed by raising the temperature well above the gelation temperature.
中文翻译：
已经证明了一种对环境敏感的聚合物网络，可以并入一种无机盐水合物相变材料（PCM）。这种材料的独特之处在于聚合物凝胶能够同时在较低温度下提供液态盐水合物相的形状稳定性，并能够响应温度升高而可逆地调节其组装强度。这种方法能够方便地控制PCM凝胶系统的粘度，从而允许以液态填充和除去混合物，但可以在固体/凝胶状态下操作。该系统由溶解在三水合硝酸锂（LNH）（一种高潜热盐水合物PCM）中的聚乙烯醇（PVA）组成。动态光散射（DLS）和粘度测定法研究表明，在稀溶液中，PNH链在LNH中比在水中更富集。在PVA浓度为15 wt％的情况下，PVA / LNH系统与PVA水溶液不同，它会胶凝并显示出温度触发的凝胶到溶胶的转变。仅用水解度最高（98％）的PVA才能实现胶凝，通过DLS和流变学测定，胶凝温度为20±1°C。ATR-FTIR光谱显示，与PVA水溶液相比，由于LNH中PVA链的脱水作用，PVA胶凝作用得到增强。物理交联的PVA / LNH凝胶在十个LNH熔融/冻结循环中表现出高度可重复和可再现的性能，如差示扫描量热法（DSC）所示。综上所述，这些结果证实了基于PVA的凝胶是承载无机PCM的有前途的基质，这些无机PCM可以承受反复的熔化/冷冻循环， |
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