Design,Synthesis And Performance Research Of Polydiacetylene And Vanadium Dioxide Composite Materials

Energy conservation and emission reduction are essential to the sustainable development of economy and society.In recent years,due to the excessive use of building services such as air conditioning,heating,lighting,and ventilation,building energy consumption has become a major"energy consumer".Promoting building energy conservation is an important measure to achieve the goal of energy conservation and emission reduction.As the main channel for heat exchange between the building and the outside world,windows account for more than half of the energy loss and are the least energy-efficient components in the building.In order to reduce the energy consumption of windows,"smart windows"that can intelligently adjust the heat exchange between windows and the outside world came into being.It can greatly improve the utilization rate of solar energy in windows and the comfort of living,which is of great significance for promoting building energy conservation.Vanadium dioxide（VO₂）,an inorganic thermochromic material,which can undergo reversible phase transition with the change of ambient temperature,that is,it becomes a semiconductor phase at low temperatures and into a metallic phase at high temperatures.Before and after the phase transition,VO₂ has a significant adjustment effect on the near-infrared light transmittance while maintaining a high visible light transmittance.This phase change characteristic gives VO₂ excellent solar regulation ability and becomes an ideal material for manufacturing smart windows.Therefore,thermochromic smart windows based on VO₂ coating have also received extensive attention and research.However,how to obtain a VO₂ coating with high solar regulation ability and high light transmittance at the same time is a severe challenge for the smart windows research institute.In addition,the color of the VO₂ coating is brown,which is not easily accepted by people in practical applications.To improve the color problem of the VO₂ coating is of great significance for the further promotion and large-scale production application of VO₂ smart windows.Compounding is the main method to improve the color problem of VO₂ coatings.However,to obtain composite materials with beautiful colors and obvious discoloration,it is very important to choose suitable thermochromic materials for compounding.Polydiacetylene（PDAs）thermochromic polymers have the advantages of obvious color change,suitable transition temperature,high stability,and good film-forming properties.They are ideal materials for improving the color problems of VO₂ coatings.This article focuses on the PDAs/VO₂ composite system to carry out related research,select the appropriate PDAs material,adopt double-layer and multi-layer methods,and compound with VO₂ coatings to prepare composite materials.Finally,dopamine was used to modify common diacetylene monomers to obtain new PDAs materials with excellent performance,and a preliminary study was conducted on dopamine-modified PDAs/VO₂ composite materials.The main research work of this paper is as follows:1.Synthesis and thermochromic properties of modified PDAsExperiments have synthesized diacetylene monomers modified by different amine linking groups.Different PDAs powders are obtained by UV-induced polymerization.They are found to have thermochromic properties after heating.Among them,PDAs are obtained by polymerization of ethylenediamine-modified monomers.The powder has an obvious color change from blue to red,and the transition temperature is about 40°C.The ethylenediamine modified monomer is made into a film by spin coating,and polymerization is induced.The resulting film exhibits excellent thermochromic properties.On this basis,a PDAs/polyvinylpyrrolidone（PVP）double-layer composite films were prepared,and the color change effect and stability of the composite films were significantly improved.2.Preparation and characterization of PDAs/VO₂ compositeThe semiconductor phase VO₂ nanoparticles were prepared by the hydrothermal method,and the obtained nanoparticles had a small particle size（the average particle size was about32.63 nm）,and the phase transition temperature was about 68℃.The VO₂ films were prepared by roller coating with a brownish-yellow color.The PDAs/VO₂ composite films were obtained by the double-layer films composite method.As the temperature increased,the composite films showed a clear color change from blue-violet to red.This was successful changed the color of the VO₂ films.On this basis,the influence of the monomer content and the thickness of the VO₂ films on the thermochromic properties of the composite films were further explored.It was found that when the thickness of the VO₂ film was 4μm and the monomer concentration was 20 mg/m L,the composite film could maintain a relatively high visible light transmittance(T_l,lum=56.23%;T_h,lum=62.37%)and strong sunlight adjustment ability(ΔT_sol=7.64).3.Synthesis of dopamine modified monomers and preliminary research on dopamine modified PDAs/VO₂ composite materialsExperiments were designed to use dopamine to modify the carboxylic acid end groups of diacetylene monomers,and try to react with diacetylene monomers with different carbon chain lengths,and finally a series of dopamine-modified new diacetylene monomers were obtained.UV-induced monomer polymerization can obtain PDAs powders with thermochromic properties,but the discoloration phenomenon is different.Further research found that the PDAs films obtained by polymerization of dopamine-modified10,12-pentadecadiynoic acid monomer has a solar modulation effectΔT_sol=0.32(T_l,lum=84.37%;T_h,lum=86.50%).In addition,a new type of dopamine-modified PDAs/VO₂composite materials were prepared.A preliminary study found that the new type of dopamine-modified PDAs can not only improve the color of VO₂,but also improve the solar modulation effect of the composite to a certain extent(VO₂films:ΔT_sol=6.67;New PDAs/VO₂films:ΔT_sol=7.52).