Preparation Of Multi-stimuli-responsive And Conductive Hydrogel And Its Application In Soft Devices

In recent years,the development of polymer-based smart materials is an important research area in advanced materials science.Multi-stimuli-responsive hydrogels have attracted much attention of researchers due to their responsive properties to environmental changes and flexibility,and have made contributions in biomedicine,sensors,flexible robots and other fields.In this paper,three types of multi-stimuli responsive hydrogels were designed and synthesized.The responsiveness and response results of different hydrogels were studied,and different applications were developed.The main results and conclusions are as follows:（1）The PNIPAM/Ag hydrogel was prepared by free radical polymerization,where N-isopropylacrylamide（NIPAM）was used as the thermo-sensitive molecule,silver nanowire（AgNWs）synthesized via polyol method at high temperature with silver nitrate（AgNO₃）as raw material,and N,N-methylenebisacrylamide（MBA）was used as the crosslinker.The PNIPAM/Ag/PPy hydrogel was prepared by in situ polymerization to form a polypyrene（PPy）network,using PNIPAM/Ag hydrogel as the intermediate.The structure and micro morphology of AgNWs and hydrogel were analyzed by XRD,UV-vis,SEM and etc.The conductivity of NIPAM/Ag hydrogel and NIPAM/Ag/PPy hydrogel was investigated,and the conductivity of hydrogels was linearly related to the compression rate,in a certain range.The temperature-responsive performance and the recovery performance of two kinds of hydrogels were studied,in which the recovery rate of NIPAM/Ag/PPy hydrogel reached 98%.In a short period,the introduction of PPy provided the hydrogel the near-infrared responsiveness.The surface temperature of NIPAM/Ag/PPy hydrogel increased to 78℃when undergoing the near-infrared light.（2）PDMAEMA/PNIPAM bilayer hydrogel and the corresponding single-layer hydrogel were prepared by casting method,using 2-（Dimethylamino）ethyl methacrylate（DMAEMA）and NIPAM as responsive molecules in the two layers.Carbon black（CB）and Poly（sodium-p-styrenesulfonate）（PSS）are used as conductive materials of PDMAEMA layer（D layer）and PNIPAM layer（N layer）,respectively.The results showed that PDMAEMA and PNIPAM single-layer hydrogel presented different response results in temperature,p H,Na Cl and ethanol.PDMAEMA/PNIPAM bilayer hydrogel would bend in the stimuli environment mention above based on the difference of the expansion rate of the two layers,and it would recover from non-intense stimuli.The direction of bending of the bilayer hydrogel in ethanol is different from that of other kinds of stimuli.Based on the response characteristics of double-layer hydrogel and the sensitivity of temperature response,a 4-arm gripper is developed to realize the clamping and release of objects.Due to the deformation dependence and the temperature response characteristics of the bilayer hydrogel,a thermistor was developed,and the partial pressure function of the electrical apparatus was changed at different temperatures.Based on the deformation dependence of flexibility and conductivity of hydrogel,a finger movement monitor was developed to detect finger movement state（bending angle）and showed repeatability.（3）CMC hydrogels were prepared using alkaline carboxymethyl cellulose（CMC）solution and epichlorohydrin（ECH）and used as intermediates.The heterogeneous double network（H-DN）hydrogels were obtained by in situ polymerization of acrylic acid（AA）and adjustment of the content of crosslinking agents in the polymer solution.The results showed that the H-DN hydrogel possessed good mechanical properties.With the increase of crosslinking agent content,the tensile strength of the hydrogel increased,the strain rate decreased,and the swelling resistance property increased.H-DN hydrogels were responsive to solution p H and specific concentration of Na Cl solution,and the stimulation response results are reflected in swelling rate（mass change and volume change）,maximum strain rate and maximum tensile stress.The 4 kinds of H-DN hydrogels presented conductivity,which can identify different degrees of strain（10%,50%and 100%）and showed repetitiveness.Since H-DN hydrogel without cross linking agent is flexible,it is best to combine wearable and conductive properties to develop a wearable strain sensor to monitor various kinds of human movement.Based on the flexibility and conductivity of H-DN hydrogel,the capacitive pressure sensor is developed to monitor the pressure of different quality objects.With the dosage of crosslinker increased,the monitoring range of pressure sensors will also expand.Figure[51]table[9]reference[128]...