University of Notre Dame, Department of Chemical & Biomolecular Engineering, Notre Dame, Indiana 46556, United States.
Biomacromolecules. 2021 Jan 11;22(1):171-182. doi: 10.1021/acs.biomac.0c00950. Epub 2020 Aug 17.
Host-guest physical cross-linking has been used to prepare supramolecular hydrogels for various biomedical applications. More recent efforts to endow these materials with stimuli-responsivity offers an opportunity to precisely tune their function for a target use. In the context of light-responsive materials, azobenzenes are one prevailing motif. Here, an asymmetric azobenzene was explored for its ability to form homoternary complexes with the cucurbit[8]uril macrocycle, exhibiting an affinity () of 6.21 × 10 M for sequential binding, though having negative cooperativity. Copolymers were first prepared from different and tunable ratios of NIPAM and DMAEA, and DMAEA groups were then postsynthetically modified with this asymmetric azobenzene. Upon macrocycle addition, these polymers formed supramolecular hydrogels; relaxation dynamics increased with temperature due to temperature-dependent affinity reduction for the ternary complex. Application of UV light disrupted the supramolecular motif through azobenzene photoisomerization, prompting a transition in the hydrogel. Excitingly, within several minutes at room temperature, thermal relaxation of azobenzene to its state afforded rapid hydrogel recovery. By revealing this supramolecular motif and employing facile means for its attachment onto pre-synthesized polymers, the approach described here may further enable stimuli-directed control of supramolecular hydrogels for a number of applications.
主体-客体物理交联已被用于制备超分子水凝胶，以用于各种生物医学应用。最近为使这些材料具有刺激响应性而做出的努力为精确调整其针对特定用途的功能提供了机会。在光响应材料的背景下，偶氮苯是一个流行的主题。在这里，探索了一种不对称的偶氮苯，以研究其与葫芦[8]脲大环形成同三聚体配合物的能力，尽管具有负协同性，但它对顺序结合的亲和力（）为 6.21×10^M。首先从不同且可调比的 NIPAM 和 DMAEA 制备共聚物，然后用这种不对称的偶氮苯对 DMAEA 基团进行后合成修饰。大环添加后，这些聚合物形成超分子水凝胶；由于温度依赖性的三元配合物亲和力降低，温度升高导致弛豫动力学增加。紫外线的应用通过偶氮苯光异构化破坏了超分子基序，促使水凝胶发生转变。令人兴奋的是，在室温下几分钟内，通过将偶氮苯热恢复到其 态，可实现快速的水凝胶恢复。通过揭示这种超分子基序，并采用简便的方法将其连接到预先合成的聚合物上，这里描述的方法可能会进一步实现对超分子水凝胶的刺激导向控制，以用于多种应用。
