The Synthesis And Electrochromic Study Of D-A Type Copolymers Based On Benzene,benzotriazole And Thiophene Derivatives

Since the conductivity of doped polyacetylene has been discovered,substantial efforts has been centered on conductive polymers?CPs?.Subsequently,CPs are considered as crucial materials with broad application prospects,such as field effect transistors,smart windows,camouflage materials and electrochromic devices.Among CPs,electrochromic copolymers?ECs?have attracted widely attention due to reversible color changes that can occur by modifying the redox state.In addition,ECs are also extremely prevail because of their high optical contrast and coloration efficiency,short response time,fine-tuned band gap,low-cost,and malleable trait compared to inorganic metal oxides.A large amount of literature we have reviewed shows that on some level the birth of high-performance new materials depends on the design of novel and effective molecular structures,particularly the design of donor-acceptor?D-A?structures.The donor-acceptor?D-A?type molecular structure is the fact that alternates between the donor unit of the high HOMO level and the acceptor unit of the low LUMO level to prepare polymers with low bandgap values.Besides the lower bandgap value of the obtained polymer,this designing method is very helpful for promoting the optical,dynamic properties and processibility of the copolymer.In this study,we have prepared twelve copolymers,by chemical polymerization via adopting stille cross-coupling and Suzuki coupling reaction mechanism based on benzotriazole,pyrrolopyrroledione,carbazole and thiophene and their derivatives.There are PBDT-1,PBDT-2,PBDT-3,PBTE-1,PBTE-2,PBDT-3,PBDD-1,PBDD-2,PBDD-3,PCTF-1,PCTF-2 and PCTF-3.And they were carried out detailed characterization tests on their electrochromic properties.The test results show that the response time of PBDT-1 is extremely short,and the optical contrast of PBDT-3 in the NIR region is extremely high,up to 80.20%.Compared with PBDT,after replacing thiophene units with benzene,although the response time is slightly extended,PBTE-2has a very low bandgap value of just 1.55 eV,and the coloration efficiency value is very high.For example,in the NIR region,the efficiency value of PBTE-1 is up to 390.66cm²·C^-1.Retain the benzene units and bring in cyclopentadithiophene and pyrrolopyrroledione units,and the bandgap values of obtained copolymers?PBDD-1,PBDD-2 and PBDD-3?are 1.54 eV,1.55 eV and 1.53 eV,respectively.These low-bandgap copolymers like PBDD usually have higher hole mobility and photovoltaic efficiency,therefor the optical contrast of these three copolymers in the NIR region is very high.In addition to the high optical contrast and coloration efficiency,PCTF also has a varified color change,and there are different degrees of green,which will have broad development prospects in practical application.