Hydrogen Bonding And Hydrophobic Interaction Cooperatively Induced Strong And Tough Supramolecular Hydrogel With Shape-Memory Property

Hydrogel is a class of high water containing, water insoluble, chemically or physically cross-linked three dimensional soft matter. Depending on the cross-linking points, hydrogels can be divided into chemical and physical hydrogels(supramolecular hydrogels). Most of the physical hydrogels are often very weak due to the inherent poor strength of the non-covalent crosslinking points.In this thesis, strong and tough polyurethane-urea(PUU) supramolecular hydrogels were obtained by PEG, diisocyanate and aliphatic amine, which acts as chain extender, via the cooperative effect between hydrogen bonding and hydrophobic aggregation interactions. The elastic modulus of the present synthetic supramolecular hydrogels could be adjusted between 20-90 k Pa, the elongations at break range from 200% to 1200%, and the stress at breaking can be up to 4 MPa. The influence of the synergistic effect between the types of H-bonding and the length of the hydrophobic spacer on the final mechanical performances of the supramolecular hydrogels was studied in detail. In addition, the water and thermal responsive shape-memory behavior of the obtained PUU hydrogels were also studied.We also provide a new strategy toward addressing the challenges of using synthetic hydrogels to achieve biological soft tissue/hydrogel’s unique viscoelastic property-strain hardening. In this part, supramolecular hydrogels are prepared by free-radical copolymerization of acrylamide and chain-extended vinyl-modified pseudo-polyrotaxane, which acts as a multifunctional supramolecular crosslinker. The obtained hydrogels can be stretched up to 700-2500% of their original lengths before breaking and withstand a compression strain of 98% without fracture. Tensile tests show obvious strain hardening behaviours in high stretching and compression deformation regimes.