Leveraging the gel-to-sol transition of physically crosslinked thermoresponsive polymer hydrogels to enable reactions induced by lowering temperature.
Leveraging the gel-to-sol transition of physically crosslinked thermoresponsive polymer hydrogels to enable reactions induced by lowering temperature.
复制标题
利用物理交联的温敏聚合物水凝胶的凝胶-溶胶转变，以实现由降低温度诱导的反应。
作者：
已经进行了大量的工作，在使用加热来触发反应，通过温度依赖性的障碍或约束分离试剂的去除。然而，在使用冷却来实现类似目标方面所做的工作要少得多。许多应用，例如涉及易受持续低温影响的部件或材料的应用，以及无法获得加热能量的情况，都将受益于这种反向方法。因此，在这项研究中，我们探索物理交联的水凝胶是否可以可靠地用作热敏限制，使试剂仅在冷却时反应。我们通过将试剂加载到温敏水凝胶的相邻块中来实现这一点，并表明这些试剂只能在水凝胶的温度福尔斯其低临界溶解温度（LCST）后才能相互反应。在LCST以上，试剂保持隔离在单独的凝胶中，不发生反应;这种“关闭”状态在延长的时间内是稳定的。当允许系统冷却时，水凝胶液化并彼此流入，允许嵌入的试剂混合（“开”状态）。我们使用NaCl调节水凝胶的LCST，使用流变仪量化NaCl的调节效果，并确定在与调节的LCST相似的温度下可重复地触发反应。我们还展示了概括性的概念，通过探索涉及从根本上不同的反应类型的情况。因此，这一概念构成了基于冷却的自主材料行为的新方法。当物理交联的温敏水凝胶冷却至其溶解点以下时发生的凝胶至溶胶转变可用于可靠地触发嵌入其中的试剂之间的反应。
Much work has been done on the use of heating to trigger reactions via the temperature-dependent removal of a barrier or constraint separating reagents. Far less work, however, has been done on the use of cooling to achieve a similar goal. Numerous applications, such as those involving components or materials susceptible to persistent low temperatures and cases in which energy for heating is not available, would benefit from this inverse approach. Hence, in this study we explore whether physically crosslinked hydrogels can be reliably used as thermoresponsive constraints that allow reagents to react only upon cooling. We achieve this by loading reagents into adjacent blocks of thermoresponsive hydrogel and showing that these reagents can only react with each other after the temperature of the hydrogel falls below its lower critical solution temperature (LCST). Above the LCST, the reagents remain sequestered in separate gels and no reaction occurs; this “OFF” state is stable for extended periods. When the system is allowed to cool, the hydrogels liquify and flow into each other, allowing mixing of the embedded reagents (“ON” state). We tune the hydrogels' LCSTs using NaCl, quantify the NaCl's tuning effect using rheometry, and determine that reactions are triggered reproducibly at temperatures similar to the tuned LCSTs. We also demonstrate generalizability of the concept by exploring situations involving radically different reaction types. This concept therefore constitutes a new approach to autonomous material behavior based on cooling. The gel-to-sol transition that occurs when physically crosslinked thermoresponsive hydrogels are cooled below their solution point can be used to reliably trigger reactions between reagents embedded within.
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