Department of Materials Science and Engineering , Texas A&M University , 3003 TAMU, 209 Reed McDonald , College Station , Texas 77843-3003 , United States.
ACS Appl Mater Interfaces. 2018 May 2;10(17):14786-14795. doi: 10.1021/acsami.8b03080. Epub 2018 Apr 19.
Chemically cross-linked polymer matrices have demonstrated strong potential for shape stabilization of molten phase change materials (PCM). However, they are not designed to be fillable and removable from a heat exchange module for an easy replacement with new PCM matrices and lack self-healing capability. Here, a new category of shapeable, self-healing gels, "salogels", is introduced. The salogels reversibly disassemble in a high-salinity environment of a fluid inorganic PCM [lithium nitrate trihydrate (LNH)], at a preprogrammed temperature. LNH was employed as a high latent heat PCM and simultaneously as a solvent, which supported the formation of a network of polyvinyl alcohol (PVA) chains via physical cross-linking through poly(amidoamine) dendrimers of various generations. The existence of hydrogen bonding and the importance of low-hydration state of PVA for the efficient gelation were experimentally confirmed. The thermal behavior of PCM salogels was highly reversible and repeatable during multiple heating/cooling cycles. Importantly, the gel-sol transition temperature could be precisely controlled within a range of temperature above LNH's melting point by the choice of dendrimer generation and their concentration. Shape stabilization and self-healing properties of the salogels, taken together with tunability of their temperature-induced fluidization make these materials attractive for thermal energy storage applications that require on-demand removal and replacement of used inorganic PCM salt hydrates.
化学交联聚合物基质在熔融相变材料（PCM）的形状稳定化方面表现出了巨大的潜力。然而，它们不是为可填充和可从热交换模块中取出而设计的，以方便用新的 PCM 基质进行更换，并且缺乏自修复能力。在这里，引入了一类新型的可塑形、自修复凝胶，称为“盐凝胶”。盐凝胶在具有高潜热的流体无机 PCM [硝酸锂三水合物（LNH）] 的高盐环境中，在预定温度下可逆地分解。LNH 被用作高潜热 PCM，同时也用作溶剂，通过聚（酰胺-胺）树状大分子的各代的物理交联，支持了聚乙烯醇（PVA）链的网络形成。氢键的存在以及 PVA 的低水合状态对有效凝胶化的重要性通过实验得到了证实。PCM 盐凝胶的热行为在多次加热/冷却循环中具有高度的可逆性和可重复性。重要的是，通过选择树状大分子的代和浓度，可以在 LNH 熔点以上的温度范围内精确控制凝胶-溶胶转变温度。盐凝胶的形状稳定和自修复性能，以及其温度诱导的流化的可调性，使这些材料在需要按需去除和更换用过的无机 PCM 盐水合物的热能存储应用中具有吸引力。
