Preparation And Application Of Hydrophobic Association And Ionic Coordination Dual Physical Crosslinking Hydrogel

In recent years,with the continuous development and advancement of smart technology,people are paying more attention to their physical health.Various smart wearable devices that detect human movement,such as smart devices that monitor pulse beat,heart rate,and respiration,have increased their market share.As a soft material,hydrogel has a structure similar to biological tissues,and is flexible,stretchable and has good biocompatibility.Therefore,hydrogel has great application potential in the field of smart wearable devices.However,traditional hydrogels have the defect of single performance and cannot meet the demands of increasingly complex wearable device materials.Therefore,this paper developed two dual-network hydrogels based on hydrophobic association and ionic coordination.This type of hydrogel has both self-healing,self-adhesive and conductive functions,and its application in flexible sensor collars has been discussed.The specific content is as follows:In the first chapter,the anionic surfactant sodium dodecyl sulfate(SDS)and the hydrophobic monomer lauryl methacrylate(LMA)form micelles,which is free-radically polymerized with the hydrophilic monomer acrylic acid(AAc)to form a hydrophobically associated hydrogel.By adjusting the SDS content,the elongation at break of the hydrogel can reach 2087.8%,and the self-repair efficiency can reach 93.8% at 50°C.Secondly,Fe(III)is introduced into the hydrogel by immersing the electrolyte solution.The introduction of Fe(III)enhances the mechanical properties of the hydrogel.The breaking stress is as high as 841.5k Pa,and the self-repair efficiency is still above 50%.The introduction of Fe(III)also gives the hydrogel excellent conductivity.The strain sensor based on the hydrogel shows high sensitivity in a wide strain range of 0-200% to 200-500% and 500%-900%(GF is 0.53,1.23,2.09,respectively)and it still maintains rapid response and good stability after repeated loading-unloading tests.In addition,the single-sided adhesion hydrogel can be obtained by adjusting the amount of SDS,and the nature of single-sided adhesion can effectively reduce the noise generated by the movement,so that the signal for monitoring the subtle movement is more accurate.In the second chapter,the cationic surfactant cetyl ammonium bromide(CTAB)and the hydrophobic monomer LMA form micelles,which are copolymerized with acrylic acid radicals to form a hydrophobically associated hydrogel.CTAB can form a strong electrostatic interaction with the negatively charged carboxyl groups on the polyacrylic acid(PAA)chain.The maximum breaking stress and breaking elongation of the hydrogel can reach 402.5k Pa and 1296.3%.In addition,the hydrogel has a self-repairing efficiency of 90% at room temperature for 24 hours;by applying CTAB solution on the section,the system can achieve a completely self-healing effect.Subsequently,construct a second cross-linking network by introducing Fe(III)to form an ionic coordination bond with PAA long chain.The construction of the second network significantly improves the mechanical properties and gives the hydrogel excellent conductivity.The crack strength can reach 880.5 k Pa and the elongation at break is1173.2% and self-healing efficiency is above 43% The strain sensor based on the hydrogel shows high sensitivity in a wide strain range of 0-300% and 300-600%(GF is 0.49 and 0.93,respectively),and it still maintains fast response and good stability under multiple cycles of loading-unloading tests.