Faculty of Chemistry, Biological and Chemical Research Center, University of Warsaw, 101 Żwirki i Wigury Av., P.L. 02-089 Warsaw, Poland.
J Mater Chem B. 2022 Jun 15;10(23):4463-4472. doi: 10.1039/d2tb00534d.
We successfully synthesized a novel hydrogel based on derivatives of natural α-amino acids: ornithine and cystine. To make ornithine attachable to the polymer chain, the δ-amino group was modified with an acryloyl group and the main monomer was obtained. From cystine, the cross-linker ,'-bisacryloylcystine was obtained. Then, by free radical polymerization of the monomers in the presence of Fe, the hydrogel was obtained. The presence of iron ions in the pre-gel solution accelerated the decomposition of a free radical initiator (ammonium persulfate) and allowed uniform distribution of complexed Fe in the hydrogel to be obtained. The presence of free α-amino acid groups in the main monomer and then in the polymeric network of the gels enables this complexation. As a result, the obtained hydrogel benefits from the chemical and physical cross-links, disulfide bonds, and metal-ligand complex, respectively. The composition of the hydrogel was optimized to obtain improved mechanical properties and self-healing ability. Thereby we identified a hydrogel exhibiting fast and conclusive self-healing, which recovered approximately 99% (efficiency of self-healing based on fracture strain) of its original properties after 15 min. The conductivity and electrical response of the hydrogel were investigated. The results revealed a rapid electrical response to minor stretching of the hydrogel, allowing it to be used as a strain sensor. In addition, the presence of the disulfide bonds in the hydrogel structure enabled the hydrogel to degrade in a redox environment.
我们成功地合成了一种基于天然α-氨基酸衍生物的新型水凝胶：鸟氨酸和胱氨酸。为了使鸟氨酸能够连接到聚合物链上，我们对δ-氨基进行了丙烯酰化修饰，得到了主单体。从胱氨酸中，我们得到了交联剂，双（丙烯酰基）胱氨酸。然后，通过单体在 Fe 存在下的自由基聚合，得到了水凝胶。预凝胶溶液中的铁离子加速了自由基引发剂（过硫酸铵）的分解，并允许在水凝胶中获得络合的 Fe 的均匀分布。主单体中存在游离的α-氨基酸基团，然后在凝胶的聚合物网络中存在，这使得这种络合成为可能。因此，所得到的水凝胶分别受益于化学和物理交联、二硫键和金属配体络合。优化了水凝胶的组成，以获得改善的机械性能和自修复能力。由此，我们确定了一种具有快速和决定性自修复能力的水凝胶，在 15 分钟后，其原始性能恢复了约 99%（基于断裂应变的自修复效率）。研究了水凝胶的导电性和电响应。结果表明，水凝胶对轻微拉伸具有快速的电响应，使其可用于应变传感器。此外，水凝胶结构中二硫键的存在使水凝胶能够在氧化还原环境中降解。
