Study On Synthesis And Electrochrom IC Properties Of DPP-Based Polymeric Materials

Organic electrochromic polymer materials are rich in sources,rapid response,high contrast,easy processing,low cost and many other advantages,will become an important future development direction of electrochromic materials.Since the 1970 s conductive polymer has been discovered by scientists,the development is very rapid.It becomes an important direction for future electrochromic materials.The degree of richness of the color determines,to a large extent,the prospect of the discolored material in reality.However,traditional polymer electrochromic materials generally have only a single absorption peak,limiting their application in the display field.The polymer with donor-acceptor structure usually has a double absorption peak,which can be one of the three primary colors of green,broadening the color gamut of the material and in the field of display applications.Thus,the donor-acceptor structure of the conductive polymer is gradually applied to the field of organic electrochromic.In this paper,the polymer with donoracceptor structure was synthesized by using DPP as the basic material.The electrochromic properties of the polymer were studied,and the discoloration mechanism was studied.The main contents are as follows:1.Two kinds of polymer materials with donor-acceptor structure were synthesized by selecting appropriate donor and acceptor units with DPP,PDPPPh-NT and PDPP-BDT-NT.For PDPP-Ph-NT,the electrochromic effect is best when the ratio is 2: 1,the absorption peak is at 730 nm,the thermal decomposition temperature is 377 ?,the HOMO and LUMO are-5.18 eV-3.75 eV.For the PDPP-BDT-NT materials,three kinds of materials with the ratio of 4: 1,1: 1 and 1: 4 were synthesized.The thermal decomposition temperature of the three materials was about 370 ?.With the increase in the ratio of donor and acceptor,the absorption peak is red-shift.The HOMO and LUMO of the three materials are-5.6 eV and-4.1 eV(4: 1),-5.69 eV and-4.2 eV(1: 1),-5.78 eV and-4.39 eV(1: 4).2.The electrochromic properties of PDPP-Ph-NT and PDPP-BDT-NT were studied and the response of PDPP-Ph-NT was faster and the change of absorption spectrum was more significant under the same bias voltage.At the same time,by adjusting the ratio of donor and acceptor in PDPP-BDT-NT,it was found that the material containing more donor units was more likely to undergo electron transfe,and had better electrochromic properties.The above results indicate that the donor and acceptor units have an effect on the electrochromic properties of the material.In order to further explain the effect of donor and acceptor units on the electrochromic properties of materials,the electron cloud distributions of PDPP-Ph-NT and PDPP-BDT-NT in HOMO and LUMO were calculated by density functional theory.Theoretically,the effect of the donor and acceptor unit on the electrochromic process is explained.And the experiment of doping the acceptor material(1,4-dibromo-2,5-difluorobenzene)in PDPP-Ph-NT was designed.It was found that the electrochromic performance of PDPP-Ph-NT decreased,and the conjecture was verified experimentally.Through the above experiments and analysis,we found that in the DPP conductive polymer with donor-acceptor structure,the interaction between the donor unit and the acceptor unit strength will affect the electrochromic properties of the material.When a bias is applied to the polymer,the material that interacts weakly between the donor and the acceptor is more likely to lose electrons,and the electrochromic nature is better.Therefore,we believe that by adjusting the D unit and A unit,to adjust the interaction between them,thereby affecting the material's electrochromic properties.