Preparation Of Conductive Hybrid Hydrogrl Based On Polyacrylate And Its Wearable Applications

Flexible electronics have attracted a great deal of attentions due to their unique advantages of light weight and wearability.The softness and biocompatibility of hydrogels make them ideal for bio-wearable flexible electronics.Polymer-based hydrogels could exhibit a variety of functions,such as conductivity,antibacterial,energy storage and anti-freeze.Among different polymers,polyacrylate is often used as the matrix for functional hybrid hydrogels owing to its ease of polymerisation,adjustable chain segments,non-toxicity,flexibility and excellent weather resistance.However,hydrogels are susceptible to external factors such as friction and bending during,which could cause damage and lose their functions and shorten their service life,eventually.In order to solve the aforemention problems,this thesis designed and prepared conductive hybrid hydrogels with self-healing function.In this thesis,polyacrylate with adjustable chain structure was prepared as the matrix of the hybrid hydrogel by adjusting chain segment of polyacrylate,and metal ions were used as the cross-linking agent and conductive medium to gain excellent mechanical conductive properties.Considering the diversity of application environments,modified micro-nanoparticles（mesoporous silica,microcapsules,etc.）were further compounded into the hydrogel newwork to obtain extra function of antibacteria with controlled releasing lemon essential oil.Details of the research and results are as follows:（1）Preparation of mesoporous SiO₂/polyacrylate hybrid hydrogel and its applicationMulti-branched polyacrylate was designed and prepared as a matrix,and mesoporous SiO₂loaded with lemon essential oil（EO@AMS）and metallic aluminium ions were added together to obtain the EO@AMS/polyacrylate hybrid hydrogel.Based on the rich hydroxyl and carboxyl groups contained in the polyacrylate,multiple hydrogen bonding forms and interacts with the amino and urea groups on EO@AMS.The coordination bonds formed with aluminium ions allows the hydrogel to complete its crack repair in 8 min at 35℃-45℃.Average elongation at break and resistivity of 500%and 12.26 KΩ/cm,respectively,for the five completed hydrogel repairs.In addition,hydrogel can also be used as a wearable sensor to capture human limb activity,responding to bending and stretching of human joints and showing high sensitivity to parameters.The hydrogel maintains good sensing properties even after multiple stretching cycles.In addition,based on the slow release of lemon essential oil in EO@AMS,the hydrogel also exhibits excellent antibacterial properties,with 99.99%inhibition of both E.coli and S.aureus.（2）Preparation of colour-changing microcapsules/polyacrylate hybrid hydrogel and its applicationThe TDM/PDM/polyacrylate hybrid hydrogel was obtained by combining polyacrylate-coated thermochromic dye（TDM）and polyacrylate-coated photochromic dye（PDM）with the conductive medium zinc ion to form the matrix.The hydroxyl and carboxyl groups in the main chain of the polyacrylate react with the carboxyl and hydroxyl groups on the TDM/PDM,which could form multiple hydrogen bonds.In the mean time,coordination bonds formed with zinc ions make the hybrid hydrogel exhibit excellent self-healing properties at 35℃-45℃,which could enable the damaged parts of the hydrogel to be quickly repaired.This hydrogel can be used as a smart wearable sensor which could instantaneous response the movement of body joints.Amazingly,the TDM and PDM could display a variety of colours in response to light and/or thermal stimuli,giving the hybrid hydrogel excellent environmental response to colour change,which can be used for early warning of human health threats and monitoring changes in outdoor environmental factors.（3）Preparation of phase change microcapsules/polyacrylate hybrid hydrogel and its applicationIn this hydrogel network,polyacrylate grafted with amino silicone oil was designed and synthesized as the hydrogel matrix.A phase-change microcapsule（paraffin@Au NPs-SiO₂）was obtained by emulsifying and polymerizing paraffin wax using silica-coated nano-gold（Au NPs@SiO₂）as a Pickering emulsifier.Compounded with polyacrylate and lithium ions,the PCM@Au NPs-SiO₂/polyacrylate hybrid hydrogel network was formed with unique photo-response self-healing properties.Based on the plasmonic effect,Au NPs can rapidly convert 520 nm light energy into localized thermal energy,which promotes the rapid reconstruction of multiple hydrogen bonds and coordination bonds in the system,thus the hybrid hydrogel damage area can be repaired rapidly and precisely.The excess thermal energy from light conversion and the thermal energy generated in the system can be stored in paraffin@Au NPs-SiO₂and released when the environment temperature decreases to maintain the hydrogel in normal operation.Based on the excellent ion-conductivity,the hybrid hydrogel can respond accurately to the movement of the human finger and elbow,etc.,and can respond quickly at different operating voltages and different operating frequencies.The hybrid hydrogel maintains the high sensing sensitivity even after several reciprocal stretch/recovery cycle tests or cut/self-healing tests.