Tough Polyurethane Hydrogels with a Multiple Hydrogen-Bond Interlocked Bicontinuous Phase Structure Prepared by In Situ Water-Induced Microphase Separation

Abstract

Hydrogels with mechanical performances similar to load-bearing tissues are in demand for in vivo applications. In this work, inspired by the self-assembly behavior of amphiphilic polymers, polyurethane-based tough hydrogels with a multiple hydrogen-bond interlocked bicontinuous phase structure through in situ water-induced microphase separation strategy are developed, in which poly(ethylene glycol)-based polyurethane (PEG-PU, hydrophilic) and poly(ε-caprolactone)-based polyurethane (PCL-PU, hydrophobic) are blended to form dry films followed by water swelling. A multiple hydrogen bonding factor, imidazolidinyl urea, is introduced into the synthesis of the two polyurethanes, and the formation of multiple hydrogen bonds between PEG-PU and PCL-PU can promote homogeneous microphase separation for the construction of bicontinuous phase structures in the hydrogel network, by which the hydrogel features break strength of 12.9 MPa, fracture energy of 2435 J m⁻², and toughness of 48.2 MJ m⁻³. As a biomedical patch, the outstanding mechanical performances can withstand abdominal pressure to prevent hernia formation in the abdominal wall defect model. Compared to the commercial PP mesh, hydrogel can prevent tissue/organ adhesion to reduce inflammatory responses and promote angiogenesis, thereby accelerating the repair of abdominal wall defects. This work may provide useful inspiration for researchers to design different gel materials through solvent-induced microphase separation.