Complete pH-Dependent Shape Recovery in Cubical Hydrogel Capsules after Large Osmotic Deformations
Complete pH-Dependent Shape Recovery in Cubical Hydrogel Capsules after Large Osmotic Deformations
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DOI：
10.1021/acs.macromol.1c00650
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发表时间：
2021-10
期刊：
影响因子：
5.5
通讯作者：
V. Kozlovskaya;Bing Xue;Maksim Dolmat;E. Kharlampieva
中科院分区：
文献类型：
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作者：
V. Kozlovskaya;Bing Xue;Maksim Dolmat;E. Kharlampieva
具有可逆形状变化的聚合物胶体作为刺激响应型仿生微系统受到了越来越多的关注。我们提出了立方形聚甲基丙烯酸(PMAA)水凝胶胶囊，该胶囊在聚苯磺酸钠(PSS)诱导的渗透压差的作用下完全且可逆地坍塌。使用5μm立方体牺牲模板，通过多层组装方法合成了具有高度水合壁纳米硫蛋白的胶囊。胶囊对渗透应力的响应程度和应力去除后的形状恢复程度受网络交联度、PMAA电离和PSS浓度的控制。胶囊在小渗透压(6-20kN m-2)下通过向内弯曲而沿立方体表面变形，但它们在面和边缘完全向内弯曲，在较高渗透压(>；33kN m-2)下保留未折叠的顶点。与在pH=8时去除PSS后立即恢复形状不同，在pH=3时观察到长达3天的松弛。观察到的变形行为表明，由于初始刚性点(如顶点和边)的施加压力，变形行为具有一致的响应。我们的研究带来了关于非球形水凝胶弹性变形的基础知识，这对于开发可控输送、传感和微流体的适应性系统是必不可少的。
Polymeric colloids with reversible shape transformations have attracted increasing interest as stimuli-responsive biomimetic microsystems. We present cubical poly(methacrylic acid) (PMAA) hydrogel capsules that completely and reversibly collapse in response to osmotic pressure differences induced with poly(styrene sulfonate sodium salt) (PSS). The capsules with nanothin highly hydrated walls are synthesized through a multilayer assembly approach using 5 μm cubical sacrificial templates. The degree of capsule deformation in response to osmotically induced stresses and shape recovery upon stress removal were controlled by network crosslink density, PMAA ionization, and PSS concentration. The capsules deform alongside the cubical faces through inward face buckling under small osmotic pressures (6–20 kN m–2), but they fully buckle inward in faces and edges, preserving uncollapsed vertices at higher osmotic pressures (>33 kN m–2). Unlike immediate shape recovery after PSS removal at pH = 8, a prolonged relaxation for up to 3 days is observed at pH = 3. The observed deformation behavior suggests a uniform response to applied pressures due to initial rigidity points such as vertices and edges. Our study brings fundamental knowledge about the elastic deformations of nonspherical hydrogels, which can be essential in developing adaptable systems in controlled delivery, sensing, and microfluidics.