Study On The Preparation And Performance Of High-strength Chitosan-based Self-healing Hydrogel

Hydrogel,a soft material,is composed of polymer with three-dimensional networks and water.Hydrogels with special properties such as self-healing hydrogels,have great potential applications in electronic skin,software devices and medicine.However,the self-healing hydrogels reported so far has low mechanical strength or single performance,which greatly limits their applications.Therefore,the preparation of tough multifunctional self-healing hydrogels is still the hot and difficult problem.Chitosan is the unique alkaline polysaccharide in the nature with rich amino,hydroxyl groups.At present,there are few researches on the tough self-healing chitosan-based hydrogels.Based on the previous work,this thesis explored the unique molecular structure of chitosan to prepare a tough self-healing chitosan-based hydrogel.The main research contents are as follows:1.The dibenzaldehyde-terminated poly(ethylene glycol)(DBPEG)was synthesized as a gelator to form the fisrt network through the Schiff base reaction between the N-carboxyethyl chitosan(CEC)and DBPEG.Meanwhile the monomer acrylamide of the second network was introduced and a tough CEC-DBPEG/PAM double network hydrogel was obtained by the in situ free radical polymerization.Tensile stress-strain experiments show that the hydrogel has excellent mechanical performance:the elongation at break can reach 4600%and the fracture strength could reach 460KPa.Self-healing and shape memory studies have shown that the hydrogels have self-healing and pH?metal ions responsive shape memory.2.A physically cross-linked hydrogel CEC/PAA-Fe3+ with fast self-healing was prepared by one-pot free radical polymerization through the hydrogen bonds between CEC and AA and multi-metal-carboxylate coordination bonds.FT-IR spectroscopy showed that both hydroxyl and carboxyl groups of CEC were involved in coordination with Fe3+.Loading-unloading tests showed that the CEC/PAA-Fe3+physical hydrogel has good toughness and self-recovery properties.Self-healing studies of the hydrogels showed that the self-healing efficiency of healed gels within 2.5h At 35 °C can reach more than 98%.