| Due to the ultra-high water absorption,flexible responsiveness,excellent biocompatibility and chemical stability,hydrogels are widely used in biomedical,seawater desalination,sanitary products and other fields.Owing to its hydrophilic amide group and hydrophobic carbon chain,poly(N-isopropylacrylamide)(PNIPAM)hydrogel shows excellent temperature-response,which makes it a promising substitute for inorganic thermochromic materials.However,as a functional material,similar to most hydrogel,the limited mechanical strength,fracture susceptibility and single response limit their applications in sensors,actuators,coatings,optics,electronics and water collectors.Therefore,the modification of PNIPAM hydrogel has a promising prospect.In this paper,PNIPAM hydrogel was comprehensively studied,the simple responsiveness and limited mechanical strength of PNIPAM hydrogel,which were modified by the physical mixing of MXene and polyacrylamide(PAM).MXene/PNIPAM hydrogel has light,thermal double response,which was prepared by physical doping techniques,and the optimum MXene doping amount was 200 μL of suspension,and the optimum reaction time was 24 h.The doped sample has the ability of broad band solar light absorption response.The light and thermal double response ability of the hydrogel has been greatly improved under simulated sunlight.SEM images showed that the doped hydrogel still showed three-dimensional pore structure,and it was found that the pore gradually decreased with the increase of MXene content;The rheological results showed that the mechanical strength of hydrogels is improved due to the doping of MXene;The thermal image results showed that the temperature of the MXene-doped gel increased significantly under the simulated solar irradiation.Compared with the single PNIPAM hydrogel,the process of gel phase transformation was accelerated under the synergistic photothermal effect.MXene-doped PNIPAM/PAM composite hydrogel(MXene/PNIPAM/PAM composite hydrogel)was prepared by physical mixing technique,and the optimal ratio of PNIPAM microgel solution to water was determined to be 3:1.The optimal doping amount of MXene was 200μL suspension.SEM images showed that PNIPAM microgel was uniformly dispersed in the pores of PAM gel matrix which did not change the structure of PAM gel matrix.The rheological results show that the composite hydrogel has excellent mechanical properties(mechanical strength,morphological stability),and the energy storage modulus is as high as 0.01 MPa.The thermal images and the physical images show that the composite hydrogel has photochromic ability.The UV-Vis-NIR spectra indicated that it had thermochromic ability.In general,we designed a phase change material(MXene/PNIPAM/PAM composite hydrogel)to control the heat and transmittance of sunlight through both light and thermal response in this work.In the solar modulation system,MXene is the photothermal material which acts as a light switch to stimulate the thermochromic hydrogel.PNIPAM microgel as an smart responsive material which was embedded in a highly transparent PAM hydrogel matrix.We designed the photothermal materials not only have excellent optical properties(transmittance,uniformity)and mechanical properties,but also the transmittance of the gel is uniform and controllable by adjusting the ambient temperature or light intensity.At present,there is no nano-photonic material that can combine the advantages of these two materials to obtain more solar energy effectively.However,the MXene/PNIPAM/PAM composite hydrogel introduced in this paper combines both the absorption properties of hydrogel(absorption range: 1500-2500nm)and the absorption properties of MXene(absorption range: 250-1400nm)combined to achieve a wide band of strong absorption characteristics,which has an important significance for the utilization of solar energy. |
