Luo Yi, Pauer Werner, Luinstra Gerrit A
Institut für Technische und Makromolekulare Chemie, Universität Hamburg, 20146 Hamburg, Germany.
Gels. 2023 Aug 28;9(9):695. doi: 10.3390/gels9090695.
Self-healing, thermoresponsive hydrogels with a triple network (TN) were obtained by copolymerizing N-isopropyl acryl amide (NiPAAm) with polyvinyl alkohol (PVA) functionalized with methacrylic acid and N,N'-methylene bis(acryl amide) crosslinker in the presence of low amounts (<1 wt.%) of tannic acid (TA). The final gels were obtained by crystalizing the PVA in a freeze-thaw procedure. XRD, DCS, and SEM imaging indicate that the crystallinity is lower and the size of the PVA crystals is smaller at higher TA concentrations. A gel with 0.5 wt.% TA has an elongation at a break of 880% at a tension of 1.39 MPa. It has the best self-healing efficiency of 81% after cutting and losing the chemical network. Step-sweep strain experiments show that the gel has thixotropic properties, which are related to the TA/PVA part of the triple network. The low amount of TA leaves the gel with good thermal responsiveness (equilibrium swelling ratio of 13.3). Swelling-deswelling loop tests show enhanced dimensional robustness of the hydrogel, with a substantial constancy after two cycles.
通过在低含量（<1 wt.%）的单宁酸（TA）存在下，使N-异丙基丙烯酰胺（NiPAAm）与用甲基丙烯酸和N,N'-亚甲基双丙烯酰胺交联剂官能化的聚乙烯醇（PVA）共聚，获得了具有三重网络（TN）的自愈合、热响应水凝胶。最终的凝胶通过在冻融过程中使PVA结晶而得到。X射线衍射（XRD）、差示扫描量热法（DCS）和扫描电子显微镜（SEM）成像表明，在较高的TA浓度下，结晶度较低且PVA晶体的尺寸较小。含有0.5 wt.% TA的凝胶在1.39 MPa的张力下的断裂伸长率为880%。在切断并失去化学网络后，它具有81%的最佳自愈合效率。逐步扫描应变实验表明，该凝胶具有触变性，这与三重网络的TA/PVA部分有关。低含量的TA使凝胶具有良好的热响应性（平衡溶胀率为13.3）。溶胀-去溶胀循环测试表明水凝胶的尺寸稳定性增强，在两个循环后具有显著的恒定性。
