Chain Entanglements and Hydrogen Bonds in Carbopol Microgel Reinforced Hydrogel

Physical interaction between the microgel and the hydrogel matrix is a key issue in the rational design of microgel reinforced hydrogels. A pentaerythritol-crosslinked poly(acrylic acid) (PAAc) microgel, named Carbopol, is composited with polyacrylamide (PAAm) hydrogel. The toughness of the hydrogel is significantly improved by constructing an interpenetrating network of Carbopol and PAAm. Chain entanglements within the composited hydrogel result in a strain-hardening phenomenon and an efficient stress transfer from the PAAm matrix to the sacrificing network of Carbopol. Hydrogen bonds between PAAc and PAAm can be formed in an acidic environment, which function as reversible sacrificing bonds and further improve the stretchability of the hydrogel.