Elastic Polymeric Hydrogels via Sparse Chain Entanglements and Hydrophobic Aggregates

Highly resilient polymeric hydrogels have shown vast potential in the fields of soft robots and wearable devices. However, the inherent interchain entanglements in the polymer network usually accompany energy dissipation during large deformation to result in obvious hysteresis. In this work, a facile strategy is proposed to modulate the degree of chain entanglement and construct potent noncovalent crosslinking points in the polymer network to afford the preparation of elastic and fatigue resistant hydrogels (PAPL hydrogels). The decrement in the polymer molecular weight controlled by initiator concentration in the radical polymerization system of acrylamide (AM) and N-acryloyl-L-phenylalanine (APA, a hydrogen bonding reinforced factor) cannot only minimize the spatial entanglements but also induce the formation of potent hydrogen-bond (APA-APA and APA-AM) assisted hydrophobic aggregates. The resulting PAPL hydrogel exhibits tensile strength of 310 kPa, fracture strain of 1050%, and hysteresis <5.4% at 800% strain, and could withstand long-term stimulation of successive tensile and compression deformation with negligible mechanical attenuation. As a flexible sensor, the PAPL hydrogel demonstrates an ultralow detection limit (tensile strain of 0.1%), rapid electromechanical response (≈16.6 ms), and could precisely monitor both tiny and large human activities.