AN AMPHIPHILIC ENTANGLED NETWORK APPROACH FOR ULTRATOUGH HYDROGELS

Abstract

In this thesis, a general approach to fabricating hydrogel with high toughness and amphiphilic properties is presented by introducing semi-crystalline hydrophobic chains into a hydrophilic network based on entropy-driven miscibility. High molecular weight PEGDA and PLA are premixed in an organic solvent, followed by a crosslinking process to create a hydrogel network. The entanglements between PEGDA and PLA chains are preserved in gelation, acting as slip links and enhancing the hydrogel's stress distribution. When immersed in water, the hydrophobic PLA chains cluster together to form semi-crystalline structures. These in-situ-formed semi-crystalline domains are intricately interwoven into the hydrophilic networks through chain entanglements, providing additional physical crosslinks and stiffening the hydrogel. This hydrogel exhibits high toughness (fracture energy ranging from 1.2 to 3.9 MJ/m³), strength (modulus between 0.15 and 4 MPa), fatigue resistance (11% hysteresis), along with a substantial swelling ratio of 6 to 10. This toughening approach provides hydrogels with improved mechanical properties and amphiphilic nature, offering a new design concept in advanced hydrogel.