Tough Hydrogels Based On N-Isopropylacrylamide Polymer

Hydrogel has been applied in various fields in recent years due to its special structure.However,the mechanical properties of traditional hydrogels are poor,which restricts its further use greatly.In this paper,PAA/NIPAAM-co-DMA,PVA/NIPAAM-co-DMA and ADN three kinds of high toughness gels were prepared by using N-isopropylacrylamide(NIPAAM)as the monomer.The obtained hydrogels were endowed with temperature response,frost resistance,antibacterial respectively.The properties of gels were studied systematically by tensile stress strain test and shear adhesion test and their applications were also explored..The main work and conclusions are as follows:(1)The copolymers of DMA and NIPAAM(NIPAAM-co-DMA)were synthesized by random copolymerization and introduced into acrylic acid(AA)system as crosslinker.With the help of numerous non-covalent interactions in the network,the breaking elongation could reach about 6000%and the hydrogels exhibited self-healing,notch resistance and fatigue resistance properties.Due to a large number of catechol groups on DMA,hydrogels were endowed with excellent adhesive abilities and could adhere on different types of surfaces.The isopropyl and acrylamide groups of NIPAAM enabled the mechanical properties,adhesion and viscoelasticity to be tuned by temperature.After introducing lithium chloride(LiCl)into the system,the hydrogel exhibited good electrical conductivity.It could be used as a skin sensor to detect human movements.(2)Crosslinker DMA-co-NIPAAM was introduced into polyvinyl alcohol(PVA)system to build high toughness organogel/hydrogels with dimethyl sulfoxid(DMSO)and water.With the help of DMSO and water mixed solvents,the prepared gel had frost resistance and the toughness was about 1 MJ/m3 at 32 degrees below zero.The thermal plasticity of PVA enabled the gel to remold after heating-cooling cycle and endowed the hydrogels with anti-swelling ability.In addition,the gel exhibited adjustable mechanical properties at different pH because of the response to acid or alkali environment from dopamine.(3)A high-performance hydrogel was prepared by in-situ polymerization with cationic(3-Acry lamidopropy l)trimethy lammonium chloride(DMAPAA-Q),NIPAAM and AA.The electrostatic interaction between the carboxyl group and quaternary ammonium group endowed the hydrogel with good mechanical properties(breaking elongation was about 5000%)after soaking for a long time.With the help of positive ions,the hydrogel exhibited certain antibacterial activity.The acrylamide group on the NIPAAM played a role in the formation of hydrogen bonding so that the hydrogel was endowed with the high toughness,notch resistance and fatigue resistance.The toughness could maintain about 900 KJ/m3 after 10 times of cyclic stretching.In addition,due to the reversibility of non-covalent interaction,hydrogels could be stretched to 5000%after healing for 24h.