Design And Preparation Of 3,4-ethylenedioxythiophene-based Conjugated Polymers With Reticular Structure And Their Application In Optoelectronic Devices

With the development of the times,mankind’s demand for energy is increasing day by day.The development and use of traditional energy sources has led to the depletion of resources and increased environmental pollution.Renewable energy sources such as solar,wind and tidal energy have been developed and utilized,but these clean energy sources are often unstable due to weather,climate and geographical influences.In order to make such energy sources continuous and stable,it is necessary to address the issue of system storage.Therefore,it is important to develop renewable and clean energy sources on the one hand and to save energy on the other.Supercapacitors are often used as energy storage devices for clean energy due to their long cycle life,high power density and rapid charging and discharging;electrochromic devices have been widely used in buildings,vehicles and other facilities by adjusting their own color and transmittance changes.Therefore,the development of electrochromic-supercapacitor devices with dual functions by integrating supercapacitors with electrochromic is one of the important research directions in the field of energy storage.Based on this,this thesis aims at the development of multifunctional electrochromic-supercapacitorbifunctionalmaterials:poly（3,4-dioxoethylenethiophene）（PEDOT）class materials with superior cycling stability,good flexibility and high stretchability are selected to synthesize new molecules with different structures through a new design strategy,and the influence of structure on performance is explored;around the stability of the assembled devices,the research on the improvement of molecular design strategies,electrochromic properties,capacitive properties,etc.is carried out around the issues of stability of assembled devices,performance enhancement of devices,etc.Details of the research are as follows.1.The precursor tris[4-（3,4-ethylenedioxythiophene）phenyl]amine（TPAE）was designed and synthesized using a star-shaped triphenylamine as the core and three 3,4-ethylenedioxythiophene molecules as the end groups,and the polymer PTPAE was obtained by one-step low potential electrochemical polymerization in a boron trifluoride ethyl ether（BFEE）system.Compared to EDOT and triphenylamine molecules,PTPAE has a lower starting oxidation potential（0.45 V）,which facilitates the preparation of high-performance polymer films.Unfortunately,however,the capacitive stability of the polymer film was poor（only 41%of the electroactivity was maintained after 1000 cycles）,probably due to the cluster-like structure of the polymer and the small electroactive area.So only electrochromic devices were assembled and the devices exhibited good electrochromic properties.2.Based on the first work,we conjectured that the poor performance was due to the less than ideal polymer structure,which did not give the desired net structure,so in this chapter of work we chose twisted bithiophene as the core,connected to four EDOT units,to extend the conjugated structure and create an extended network.The monomers 2,2,5,5-（3,3-bisdithiophene）-（3,4-ethylenedioxythiophene）（BT-4EDOT）were electrochemically polymerized to obtain their corresponding polymers P（BT-4EDOT）.The reticulated porous structure of P（BT-4EDOT）facilitates the entry and exit of ions and can reduce the loss of mass during the expansion and shrinkage of the film,which is conducive to improving the film’s stability.P（BT-4EDOT）obtained by electrodeposition in the BFEE system exhibits a low starting oxidation potential（0.43V）,high cycling stability（97%electrochemical activity after 2000 cycles;92%activity after 5000 cycles）,fast and reversible color change（switching time less than 1 s）in the electrochromic performance test,and high optical contrast.In the electrochromic performance tests,this is reflected in fast and reversible color change（switching time less than 1 s）,high optical contrast（55%at 500 nm）,high coloring efficiency(355 cm²C^-1),good stability,and in the capacitive performance tests,good multiplicative performance,high specific capacitance(220 F g^-1),and excellent capacitive stability（after 2000 cycles,the specific capacitance remains at 92%of the initial specific capacitance）.Based on these tests,the electrochromic-supercapacitor dual-function device was assembled,which exhibits high and stable performance and allows for the monitoring of power levels（fully charged and partially charged states）through color changes.3.In the work of the previous two chapters,the combination of an EDOT molecule with excellent stability and a molecule with high specific capacitance was chosen to obtain a reticular structured conjugated polymer,and it was already foreseen that this combination could achieve both stability and capacitive performance.However,due to the star-like structure of the triphenylamine molecule,the resulting polymer is clustered and does not have a large active area,and does not exhibit the desired capacitive performance;the selected bithiophene backbone satisfies the reticular structure of the polymer P（BT-4EDOT）,which exposes more active sites,and the stability and capacitive performance of P（BT-4EDOT）is improved over that of PEDOT alone,but the bithiophene itself the capacitive properties are less satisfactory.Therefore,in this chapter,we propose a design strategy to construct a dual network of conjugated polymers by combining PEDOT and polyaniline with excellent capacitive properties.Firstly,2,5-bis（2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl）aniline（2,5-EAE）,a monomer with the aniline unit as the core and two EDOT units as the capping unit,was synthesized,followed by a one-step electrochemical polymerization at low potential to obtain the P（2,5-EAE）double network.The existence of the double network structure provides for the enhancement of electrochemical properties and stability.In addition,we have explored the chemical reaction mechanism by quantitative calculations and Fourier transform infrared（FT-IR）spectroscopy,and systematically tested the electrochemical polymerization behavior of the precursors,with a low starting oxidation potential（0.66 V）in the BFEE system,good cycling stability（less than 10%loss of electroactivity after 5000 cycles）,which is reflected in the electrochromic performance tests as rapid reversible color change,In the electrochromic performance test,it shows fast reversible color change,high optical contrast,high coloring efficiency(322 cm² C^-1 at 610 nm)and excellent stability,and in the capacitive performance test it shows good multiplicative performance,high specific capacitance(357 F g^-1)and excellent capacitive stability.Based on these tests,a flexible patterned electrochromic-supercapacitor bifunctional device was assembled,which exhibits high stability and allows for the monitoring of power levels（fully and partially charged）through colour changes.