Study On The Application Of Large Coplanar Electron Donor In The Preparation Of Electrochromic Polymers

Conductive polymers have been developed rapidly in recent decades.Researchers have done a lot of research on their conductive type,mechanism and conductivity.At present,it has been widely used in optoelectronic devices,sensors,molecular wires,thermoelectricity,energy,biomedicine,drug release and other fields.In the field of electrochromism,our research group has carried out in-depth and extensive research on conductive polymers,and achieved fruitful results.In this article,we use materials containing large coplanar structures as polymer donors in order to obtain new high-performance electrochromic materials with novel structures,high solubility,easy processing and stable cycles.Through the donor acceptor（D-A）mode,the electron rich donor unit and electron deficient acceptor unit are combined alternately to form a molecular structure with large delocalizedπbond,which increases the delocalization degree of the conjugated polymer,makes the electrons easier to migrate,improves the conductivity and effectively reduces the band gap of the electrochromic polymer,so as to obtain excellent photoelectric materials.In this paper,a series of conductive conjugated polymers were synthesized by chemical polymerization,and their photoelectric properties were characterized.In the second chapter,we used dodecylbenzotriazolothiophene as acceptor unit,3,4-propylenedioxythiophene and dithieno[3,2-b:2,3-d]pyrrole as the donor unit.Three different polymers,PTTIN-1,PTTIN-2 and PTTIN-3,were obtained by stile palladium catalyzed coupling reaction by changing the feed ratio of the three monomers.The three polymers have obvious color changes:the color of PTTIN-1 and PTTIN-2 changed from purple to gray blue and then light blue,PTTIN-3 changed from purple to dark purple and finally changed to light blue.The three conductive polymers have high optical contrast and stability in the visible and near-infrared regions,and the initial oxidation potentials of the three materials are less than 0.75 V,their coloring efficiency in the near-infrared region is more than 450 cm²·C^-1.Combined with their low band gap values,the three materials have bright prospects in the electrochromic.In the third chapter,we successfully synthesized three novel solution processable donor acceptor conjugated copolymers PCPT-1,PCPT-2 and PCPT-3 by using dithienocyclodecadiene（DTC）derivatives and benzotrithieno[3,2-b]thiophene（TTT）derivatives as donor units and thiophenpyrrolo[3,4-c]pyrroledione（DPP）derivatives as acceptor units.The results show that the polymer has excellent photoelectric properties besides easy processing.The optical band gaps of the three polymers are lower than 1.5 e V,and they all show rich color changes.During the oxidation process,PCPT-1 changes from neutral purple to oxidized cyan gray,PCPT-2 changes from purple to gray blue and then to earth brown,PCPT-3 changes from purple to cement gray,and finally changes to light blue.All the polymers have high coloring efficiency.In the dynamic stability test of 750 cycles（6000s）,the three polymers all have good stability,and the contrast of polymer PCDT-1 at570nm reaches an amazing 96.17%.These results indicate that the synthesized polymers have satisfactory properties,which is of great significance for the application and development of electrochromic polymers.In the fourth chapter,three D-A type polymers,PCDT-1,PCDT-2 and PCDT-3,were synthesized by chemical polymerization from three monomers:benzotrithieno[3,2-b]thiophene（TTT）derivatives and dithienocyclodecadiene（DTC）derivatives as donor and selenophene Pyrrolo[3,4-c]pyrrole-dione as acceptor.It is worth mentioning that the initial oxidation potential of the three polymers is lower than 1 V,and the kinetic properties are very stable,especially the response time of the polymer PCDT-3is lower than 0.86 s in both visible and near-infrared regions,indicating that the electrochromic properties of the three polymers are excellent.