Preparation Of Stretchable Ionic Conductive Polymer And Its Application In Flexible Sensors

Although the traditional rigid semiconductor,metal and ceramic sensors have excellent electronic conductivity,but because of their own modulus is large,prone to mechanical fatigue and brittle fracture,poor transparency,it is difficult to meet people’s needs for comfort and visualization.In order to meet the demand of flexibility,it usually needs to be processed into nano-level ultra-thin structure or structure design,or with other flexible substrate composite,so there are high preparation cost,complicated process defects.In addition,the mismatch of Young’s modulus between high modulus electronic conductive materials and soft substrates leads to poor mechanical compatibility of some flexible electronic devices,which poses a great challenge to the wide application of electronic conductive materials.Compared with electronic conductive materials,stretchable ionic conductive polymers have a promising application prospect in flexible electronic devices because of their excellent mechanical properties,unique signal transmission mode,biocompatibility and low cost.However,existing stretchable ionic conductive polymers have several problems that are difficult to solve:ionic conductive hydrogels are easy to freeze in low temperature environment,and easy to lose water in high temperature environment,which leads to use failure;Ionic gel prepared based on ionic liquid has the risk of expensive ionic liquid and easy leakage.In view of the above problems,this thesis will carry out the following three works:1.In order to solve the problems of insufficient mechanical properties and poor resilience of ionic conductive hydrogels,a kind of polyacrylamide（PAAM）conductive hydrogel（PPAM）reinforced by natural small molecular organic acid-phytic acid（PA）was designed.Lithium chloride（Li Cl）was introduced to enhance electrical conductivity and environmental tolerance.The prepared PPAM ionic conducting hydrogel has good mechanical properties,elongation at break up to 2015%,breaking strength up to 168 k Pa.When used as a flexible strain sensor,it can accurately identify human movements,which has good application potential in the field of electronic skin2.In order to solve the problem of poor environmental tolerance of hydrogels and leakage of ionic liquid-based ionic gels,a"green"polymerizable deep eutectic solvent ionic gel（PDES）was designed.By selecting acrylic acid（AA）and ethylene glycol（EG）as hydrogen bond donors and choline dihydrogen citrate（CDC）as hydrogen bond acceptor,AA-EG-CDC PDES system was prepared.After photoinduced polymerization of PDES,deep eutectic solvent-based ionic gels（ICG）with extensibility（elongation at break:450%-1300%）,self-healing（self-healing efficiency:81%）,high transparency（light transmittance>95%）and ionic conductivity(0.8×10^-2-5×10^-2m S/cm)were obtained.Due to the characteristics of deep eutectic solvent（DES）ionic liquid in the system,ICG has the ability of strain response and temperature sensing.This strategy of dynamically regulating crosslinking density through hydrogen bonding provides a new idea for the construction of ion gels.3.Aiming at the problem that most of the stretchable ionic conductive polymers are difficult to degrade or recover,a fully physical cross-linked ionic conductive elastomer（ICE）with polyacrylic acid（PAA）as the skeleton was designed.Polyethylene glycol（PEG）was used as the solvent and aluminum nitrate nine-hydrate（Al（NO₃）₃·9H₂O）was added as the conductive electrolyte.In addition,Al（III）has coordination interaction with polymer skeleton while conducting electricity.The mechanical properties of ICE gel are enhanced by adjusting the interaction between solvent,polymer and conducting ions.Ice gel has good elongation at break of 629%,fracture strength of 929 k Pa and electrical conductivity（3.27μS/cm）.Visible light transmittance（>80%）,resilience,and only the participation of water can complete the recycling of elastomer.The prepared ICG has strain and temperature response and can recognize different liquids.