Molecularly-ordered hydrogels with controllable, anisotropic stimulus response
Molecularly-ordered hydrogels with controllable, anisotropic stimulus response
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DOI：
10.1039/c9sm00763f
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发表时间：
2019-06-14
期刊：
影响因子：
3.4
通讯作者：
Ware, Taylor H.
中科院分区：
文献类型：
--
作者：
Boothby, Jennifer M.;Samuel, Jeremy;Ware, Taylor H.
响应水刺激而在编程形状之间变形的水凝胶对于生物传感器和人造肌肉等应用具有重要意义。然而，在小尺寸尺度上编程水凝胶形状变化是一个重大挑战。在这里，我们利用液晶固有的有序能力来创建机械各向异性水凝胶；当与响应性共聚单体结合时，网络中的机械各向异性会引导形状变化以响应所需的水性条件。我们的合成策略取决于甲基丙烯酸发色液晶单体的使用，该单体可以与类似结构的不可聚合发色液晶单体结合，以改变形状变化的幅度，同时保留液晶顺序。由于凝胶的机械各向异性，这种形状变化是定向的，沿着发色堆叠方向的硬度比垂直方向的硬度高出 50%。此外，我们还表明，可以通过掺入响应性亲水共聚单体来切换这些各向异性凝胶响应的刺激类型，而不破坏向列相或排列。这些特性的实用性在聚合微结构中得到了证明，这些微结构由于微米级毛细管中的紧急有序而表现出响应高 pH 值的高斯曲率。
Hydrogels which morph between programmed shapes in response to aqueous stimuli are of significant interest for biosensors and artificial muscles, among other applications. However, programming hydrogel shape change at small size scales is a significant challenge. Here we use the inherent ordering capabilities of liquid crystals to create a mechanically anisotropic hydrogel; when coupled with responsive comonomers, the mechanical anisotropy in the network guides shape change in response to the desired aqueous condition. Our synthetic strategy hinges on the use of a methacrylic chromonic liquid crystal monomer which can be combined with a non-polymerizable chromonic of similar structure to vary the magnitude of shape change while retaining liquid crystalline order. This shape change is directional due to the mechanical anisotropy of the gel, which is up to 50% stiffer along the chromonic stack direction than perpendicular. Additionally, we show that the type of stimulus to which these anisotropic gels respond can be switched by incorporating responsive, hydrophilic comonomers without destroying the nematic phase or alignment. The utility of these properties is demonstrated in polymerized microstructures which exhibit Gaussian curvature in response to high pH due to emergent ordering in a micron-sized capillary.