Enhancing hydrogel toughness by uniform cross-linking using modified polyhedral oligomeric silsesquioxane

Abstract

The use of macro cross-linkers is one of the most effective approaches for developing tough hydrogels. However, the presence of uneven cross-linking and the resulting hydrogel inhomogeneity restrict further improvement. Here, we achieve uniform cross-linking by employing polyhedral oligomeric silsesquioxane (POSS)-grafted acrylated polyethylene glycol (PEG) as a cross-linker to enhance the toughness of hydrogels. The nano-sized hard silica core of POSS facilitates energy dissipation, and its dissolved form ensures uniform cross-linking through molecular-level dispersion. The peripheral acrylate groups introduce multiple interacting points, and the physical entanglements of long-chain PEG contribute to enhanced toughness. Incorporating acrylated POSS-PEG into polyacrylamide hydrogel yields enhanced properties such as toughness of up to 6531 kJ m−3 and break elongation up to 9455%, where the length of PEG chains grafted onto POSS is demonstrated to play a crucial role in facilitating energy dissipation and achieving high toughness.