Materials Science and Technology of Polymers, MESA+ Institute for Nanotechnology, University of Twente , P.O. Box 217, 7500AE, Enschede, The Netherlands.
J Am Chem Soc. 2017 Jul 26;139(29):10029-10035. doi: 10.1021/jacs.7b04920. Epub 2017 Jul 12.
We report on the synthesis and structure-property relations of a novel, dual-responsive organometallic poly(ionic liquid) (PIL), consisting of a poly(ferrocenylsilane) backbone of alternating redox-active, silane-bridged ferrocene units and tetraalkylphosphonium sulfonate moieties in the side groups. This PIL is redox responsive due to the presence of ferrocene in the backbone and also exhibits a lower critical solution temperature (LCST)-type thermal responsive behavior. The LCST phase transition originates from the interaction between water molecules and the ionic substituents and shows a concentration-dependent, tunable transition temperature in aqueous solution. The PIL's LCST-type transition temperature can also be influenced by varying the redox state of ferrocene in the polymer main chain. As the polymer can be readily cross-linked and is easily converted into hydrogels, it represents a new dual-responsive materials platform. Interestingly, the as-formed hydrogels display an unusual, strongly hysteretic volume-phase transition indicating useful thermal memory properties. By employing the dispersing abilities of this cationic PIL, CNT-hydrogel composites were successfully prepared. These hybrid conductive composite hydrogels showed bi-stable states and tunable resistance in heating-cooling cycles.
我们报告了一种新型的双响应型有机金属聚（离子液体）（PIL）的合成和结构-性能关系，该 PIL 由交替的氧化还原活性、硅烷桥联二茂铁单元和侧基中的四烷基膦磺酸盐部分组成的聚（二茂铁硅烷）主链构成。由于主链中存在二茂铁，这种 PIL 具有氧化还原响应性，并且还表现出具有较低临界溶液温度（LCST）型热响应行为。LCST 相转变源于水分子和离子取代基之间的相互作用，并在水溶液中表现出浓度依赖性、可调的转变温度。PIL 的 LCST 型转变温度也可以通过改变聚合物主链中二茂铁的氧化还原状态来影响。由于聚合物可以很容易地交联并容易转化为水凝胶，因此它代表了一种新的双响应材料平台。有趣的是，所形成的水凝胶表现出异常强烈的滞后体积相转变，表明具有有用的热记忆性能。通过利用这种阳离子 PIL 的分散能力，成功制备了 CNT-水凝胶复合材料。这些混合导电复合水凝胶在加热-冷却循环中表现出双稳定状态和可调电阻。
