Functional Polyurethane Hydrogel Based On Lysine-Dopamine

Polymer hydrogels are growing at a rapid pace,as synthetic equivalents for biological materials for their similarities to soft tissues in some aspects such as their flexibility and hydrated forms.Development of hydrogels with excellent and tunable mechanical properties combining with multi-functions is an intriguing issue in material science and engineering.Bio-inspired tunable sacrificial bonds were introduced into the tetraPEG based PU(TP)network to afford a hydrogel with tunable mechanical properties,shape-memory and self-healing functions.The mussel-inspired compound of Lysine-dopamine(LDA)was introduced into the network of TP hydrogel through polyurethane/polyurea chemistry to form LDA-Tetra-PEG-PU(LTP)hydrogel.As catechol groups in LDAs can intermolecularly interact with each other and can also coordinate with ferric ions with different coordination ratios by tuning the pH value,these physical interactions with different strengths in the afforded LTP hydrogel constructed kinds of sequentially tuned sacrificial bonds.As a result,these sacrificial bonds preferentially ruptured prior to the covalent network upon external loading,which dissipate the energy and endow the hydrogel with advanced and post-adjustable mechanical properties.This mechanism was investigated in detail.Dynamic mechanical behaviors of the hydrogels changes and compressive properties of the hydrogels improve with sequentially tuning the tunable sacrificial bonds.Furthermore,the LTP hydrogel showed multi-functions such as shape memory and self-healing abilities.In addition,the tetra-PEG based hydrogel showed remarkable thermo-responsiveness that the hydrogel distinctly contracted with the increase of the temperature.The improved mechanical strength and multi-functions should enlarge the application areas of the tetra-PEG based hydrogel in various fields.