Preparation And Applications Of Structural Colour Hydrogels And Adhesive Hydrogels

As a stimuli-responsive intelligent soft material,hydrogels have great application prospects in tissue engineering and actuators.However,in practical application,hydrogels need to be combined with multifunction,while in general,hydrogels are monofunctional,which is difficult to meet the requirements of practical application.Therefore,the main idea of this work is to introduce the functions of temperature sensitivity,adhesive and self-healing properties into hydrogels to endow them with versatility.Firstly,by introducing temperature-sensitive components into the structural colour hydrogels and adjusting the cross-linking density of the second network,we prepared the structural colour hydrogels with dual response of temperature and mechanics accompanied with transient colour-changing behavior.Secondly,the self-healing hydrogel supercapacitor was prepared by using physically cross-linked adhesive hydrogel as electrolyte and multi-wall carbon nanotubes?MWCNT?as electrode.Finally,the adhesive component was introduced into the shape memory hydrogel,and a shape memory actuator which could automatically capture objects through adhesion was prepared.The main contents and results of this work are as follows:1.By combination of Poly-?dodecylglyceryl itaconate?/Polyacrylamide?PDGI/PAAm?hydrogel and temperature-sensitive components poly?N-isopropylacrylamide??PNIPAm?,and adjusting the crosslinking density of the second network,we can fabricate PDGI/PAAm-PNIPAm double network hydrogel with different temperature-sensitive behaviours,and structural colour hydrogel with transient colour-changing behavior was developed.Then transparency changes of hydrogels by variable temperature ultraviolet-visible spectra in the process of temperature increase were discussed.This kind of structural colour hydrogel which combines mechanochromatic behaviour with temperature-induced colour change has a potential application prospect in the transient information encryption materials.2.The self-healing,conductive and adhesive hydrogel was obtained by physically cross-linking N,N-dimethylacrylamide?DMAA?with hectorite clay and adding lithium chloride?Li Cl?and the adhesive component?-cyclodextrin??-CD?.PDMAA/Li Cl hydrogel supercapacitor was prepared in which the hydrogel act as electrolyte and MWCNT as electrode,and its electrochemical performance was tested.The experimental results showed that the surpercapacitor has good rate capability?The specific capacitance maintained 68.5%when the current density was increased five times?,high coulombic efficiency(95.5%@40 A?g^-1),excellent self-healing properties?The electrochemical impedance curves almost overlap before and after the self-healing process?and cycle stability?remained 95.5%of the initial specific capacitance after 10000 times?.These results reflected the excellent characteristics of the hydrogel supercapacitor.3.The shape memory hydrogel with temperature-responsive tunable adhesion change was obtained by temperature-response of MC solution,in which PAAm chemical crosslinking was used as a permanent network,methyl cellulose?MC?as a reversible network and?-CD as an adhesive factor to endow hydrogel with stickiness.In addition,GO was introduced as an efficient photothermal converter to convert the temperature response into non-contact controlled near-infrared?NIR?laser response.The shape memory performance was optimized by adjusting the component content of permanent network and reversible network.When the AAm mass fraction was 15 w/v%,the shape fixity ratio reached 91.7%;when the?-CD mass fraction was 8 w/v%,the adhesive strength reached 13 k Pa.The actuator prepared can maintain temporary shape at high temperature,but was nonstick.At low temperatures the temporary shape returned and the adhesion also recovered,allowing the actuator to capture the target object and then released it by NIR laser irradiation.The combination of shape memory and adhesion provided a new idea in the design of soft actuators.