Studying On The Preparation And Properties Of Conductive Thermal-responsive Hydrogels

Conductive smart hydrogels with several virtues such as similar characters to biological tissues,sensitive response to ambient variations,have shown their excellent talents in the field of flexible electrical sensors,biomedical devices and directional transportation.However,complex preparing approaches or the instable inner structures have not only been timeconsuming,but also broken up the performance and reliability of the smart hydrogel-based devices.In this work,we have put forward a facile one-step method to synthesize a kind of conductive poly(N-isopropylacrylamide)(PNIPAM)hydrogel doped by a new green solvent of deep eutectic solvent(DES)containing quaternary ammonium salts and various hydrogen bond donors.The mechanical strength of the DES-doped PNIPAM hydrogels was drastically improved compared to the pure PNIPAM gels through the combination of DES and NIPAM,and some doped hydrogels lost the typical phase transition temperature of PNIPAM.Moreover,due to the ionic property of DES,the hybrid hydrogels also presented the thermal-depending conductivity as well as sensitive deformation response,which could be used as a smart switch in a circuit or a sensing element with environmental response ability.The cost-effective preparation and the attractive performance of the DES-doped hydrogels would offer a new avenue to construct multi-functional materials.the structures of this paper are as follows:Firstly,three different systems of DES conductive substrates were prepared by combining hydrogen bond donors AA,AAm and G with quaternary ammonium salt of hydrogen bond acceptor.The DES solution is obtained by melting hydrogen bond donors and acceptors with a certain molar ratio at high temperature,and the hydrogen bonds between synthesized DES are detected and analyzed by infrared and nuclear magnetic resonance,and the characteristic functional groups are determined.Secondly,the conductive medium DES was introduced into the temperature-responsive PNIPAM polymer system to prepare different temperature-sensitive conductive hydrogels,and the gel samples were tested for temperature sensitivity and conductive strain.Among them,the LCST,conductivity and mechanical properties of gel materials will be affected by different systems and doping amount.We quantify the phase transition temperature of gel by measuring transparency,DSC,temperature-current curve and rheological curve.At the same time,we use electrochemical workstation and tensile machine to monitor the conductivity and compressive properties of the material,and measure the current under different compressive strains.Moreover,hybrid hydrogels also have the characteristics of thermal conductivity changing with heat and sensitive deformation response due to the ionic properties of DES,which can be used as intelligent switching circuits or sensing elements with environmental response capability.In addition,the intelligent hydrogel has good conductivity and ductility,and the conductivity of doped DES will decrease with the increase of temperature,which is suitable for the construction of multifunctional sensors.