College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen 518060, P. R. China.
Soft Matter. 2021 Feb 19;17(6):1566-1573. doi: 10.1039/d0sm01703e.
Microgel-reinforced (MR) hydrogels are tough hydrogels with dispersed rigid microgels embedded in a continuous soft matrix. MR gels have the great potential to provide not only mechanical toughness but also the desired functional matrix by incorporation of various functional microgels. Understanding the toughening mechanism of the MR hydrogels is critical for the rational design of the desired functionally tough MR gels. However, our current knowledge of the toughening mechanism of MR gels mainly comes from the MR hydrogels with both chemically crosslinked dispersed microgels and a continuous matrix. Little is known about the hybrid MR gels with physically crosslinked microgels embedded in a chemically crosslinked matrix. Herein, we synthesize such hybrid MR hydrogels with the ionic crosslinked calcium alginate microgels incorporated into the chemically crosslinked polyacrylamide (PAAm) matrix. The alginate microgels show strong size and modulus effects on the toughening enhancement: the larger microgels could toughen the MR gels more than the small ones, and the microgels with medium modulus could maximize the toughness of the MR gels. By comparison of the mechanical performances of the MR and the corresponding double network (DN) hydrogels, we have proposed that the hybrid MR gels may have the same toughening mechanism as the bulk DN gel. This work tries to better understand the structure-property relationships of both MR and DN gels and help in the design of more functionally tough MR gels with the desired properties.
微凝胶增强（MR）水凝胶是一种坚韧的水凝胶，其中分散的刚性微凝胶嵌入在连续的软基质中。MR 凝胶具有提供不仅机械韧性而且通过掺入各种功能微凝胶提供所需功能基质的巨大潜力。理解 MR 水凝胶的增韧机理对于期望功能坚韧的 MR 凝胶的合理设计至关重要。然而，我们对 MR 凝胶增韧机理的现有认识主要来自于具有化学交联分散微凝胶和连续基质的 MR 水凝胶。对于嵌入化学交联基质中的物理交联微凝胶的混合 MR 凝胶知之甚少。在此，我们合成了这种混合 MR 水凝胶，其中离子交联的海藻酸钠微凝胶被掺入到化学交联的聚丙烯酰胺（PAAm）基质中。海藻酸钠微凝胶对增韧增强具有强烈的尺寸和模量效应：较大的微凝胶比小的微凝胶更能增韧 MR 凝胶，而具有中等模量的微凝胶可使 MR 凝胶的韧性最大化。通过比较 MR 和相应的双网络（DN）水凝胶的机械性能，我们提出混合 MR 凝胶可能具有与块状 DN 凝胶相同的增韧机理。这项工作试图更好地理解 MR 和 DN 凝胶的结构-性能关系，并有助于设计具有所需性能的更具功能韧性的 MR 凝胶。
