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Reversibly tuning hydrogel stiffness through photocontrolled dynamic covalent crosslinks†
Chemical Science ( IF 7.6 ) Pub Date : 2018-06-19 00:00:00 , DOI: 10.1039/c8sc02093k Joseph V Accardo 1 , Julia A Kalow 1
Chemical Science ( IF 7.6 ) Pub Date : 2018-06-19 00:00:00 , DOI: 10.1039/c8sc02093k Joseph V Accardo 1 , Julia A Kalow 1
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Controlling the physical properties of soft materials with external stimuli enables researchers to mimic and study dynamic systems. Of particular interest are hydrogels, polymer networks swollen by water with broad applicability to biomedicine. To control hydrogel mechanics with light, researchers have relied on a limited number of photochemical reactions. Here we introduce an approach to reversibly tune hydrogel mechanics with light by manipulating the stability of dynamic covalent crosslinks at the molecular level. The equilibrium between a boronic acid and diol to form a boronic ester can be altered by the configuration of an adjacent azobenzene photoswitch. By irradiating branched polymers bearing azobenzene-boronic acid and diol end groups with two different wavelengths of light, we can stiffen or soften the resulting hydrogel. Alternating irradiation induces reversible mechanical changes. Rheological characterization reveals that the hydrogels are viscoelastic, exhibiting stress relaxation on the order of seconds, and the stiffness is tuned independently of the crossover frequency. We have also demonstrated that this approach can be extended to use visible light for both softening and stiffening. These photocontrolled dynamic covalent crosslinks provide a versatile platform for tunable dynamic materials.
中文翻译：
通过光控动态共价交联可逆调节水凝胶刚度†
通过外部刺激控制软材料的物理特性使研究人员能够模拟和研究动态系统。特别令人感兴趣的是水凝胶，即水膨胀的聚合物网络，具有广泛的生物医学应用性。为了用光控制水凝胶力学，研究人员依赖于有限数量的光化学反应。在这里，我们介绍了一种通过在分子水平上操纵动态共价交联的稳定性来利用光可逆地调节水凝胶力学的方法。硼酸和二醇之间形成硼酸酯的平衡可以通过相邻偶氮苯光开关的配置来改变。通过用两种不同波长的光照射带有偶氮苯硼酸和二醇端基的支化聚合物，我们可以使所得的水凝胶变硬或软化。交替照射引起可逆的机械变化。流变学表征表明，水凝胶具有粘弹性，表现出数秒级的应力松弛，并且刚度的调节与交叉频率无关。我们还证明了这种方法可以扩展到使用可见光来软化和硬化。这些光控动态共价交联为可调动态材料提供了一个多功能平台。
更新日期：2018-06-19
中文翻译：
通过光控动态共价交联可逆调节水凝胶刚度†
通过外部刺激控制软材料的物理特性使研究人员能够模拟和研究动态系统。特别令人感兴趣的是水凝胶，即水膨胀的聚合物网络，具有广泛的生物医学应用性。为了用光控制水凝胶力学，研究人员依赖于有限数量的光化学反应。在这里，我们介绍了一种通过在分子水平上操纵动态共价交联的稳定性来利用光可逆地调节水凝胶力学的方法。硼酸和二醇之间形成硼酸酯的平衡可以通过相邻偶氮苯光开关的配置来改变。通过用两种不同波长的光照射带有偶氮苯硼酸和二醇端基的支化聚合物，我们可以使所得的水凝胶变硬或软化。交替照射引起可逆的机械变化。流变学表征表明，水凝胶具有粘弹性，表现出数秒级的应力松弛，并且刚度的调节与交叉频率无关。我们还证明了这种方法可以扩展到使用可见光来软化和硬化。这些光控动态共价交联为可调动态材料提供了一个多功能平台。
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