Synthesis,Characterization Of Fluorine-containing Thiophene Derivatives And Study On Electrochromic Properties Of Its Polymers

Electrochromism is the phenomenon where the color or opacity of a material changes when a voltage is applied.At present,electrochromic materials and technologies has been incorporated into many fields,such as smart windows,displays,automobile anti-glare rearview mirrors,military camouflage,etc.Among electrochromic materials,conductive polymers have the most application prospects because of their easy modification of molecular structure,adjustable energy band and easy processing of materials.In order to meet practical application demands,researchers have focused on designing and preparing multi-color display materials with higher optical contrast,faster response speed,and better stability.The intrinsic relationship between the microstructure and electrochromic properties（color change,response time and cyclic stability）of conductive polymers has attracted more and more attention.However,there are few reports on the influence of modification on the side chain of conductive polymer on its performance.On the other hand,many fluorine-containing organic compounds have low surface activity,good hydrophobic properties,thermal stability,oxidation resistance,and excellent weather resistance.Introducing fluorine-containing organic compounds into materials to change and improve their properties have drawn many attentions.In the first part of this paper,we designed and synthesized the fluorine-containing thiophene derivative monomer 3-（N-trifluoroacetamido）thiophene,and resolved the molecular structure of the monomer via single crystal X-ray diffraction（s XRD）analysis.The polymer film PF-TH is obtained through constant potential electrochemical polymerization,and the polymer film can change color from purple red to light blue.At a wavelength of 586 nm,the contrast of the PF-TH film is46.4%,the coloring time is 0.5 s,and the fading time is 0.4 s;at a wavelength of 1100nm,the contrast of the PF-TH film is 48.2%,the coloring time is 0.3 s,and the fading time is 0.5 s.The polymer film PF-TH is an excellent electrochromic material with fast response time.In the second part of this paper,the monomer 3-（N-trifluoroacetamido）thiophene were electrochemically copolymerized with EDOT at different molar ratios to prepare several electrochromic copolymer films P（F-TH:EDOT）s with high electrochemical activity.The surface of these copolymer films exhibits reduced hydrophilicity and enhanced lipophilic wettability.In 0.1 mol?L^-1Li Cl O₄/CH₃CN electrolyte,at a visible wavelength of 616 nm,the optical contrast of the copolymer P（F-TH:EDOT）-1/1 is55%,fading time is 0.58 s,coloring time is 0.7 s and the coloring efficiency is 167.9cm²?C^-1,which are better than that of PEDOT(contrast is 43%at 620 nm,fading time is 0.56 s,coloring time is 1.58 s,coloring efficiency is 108.1 cm²?C^-1)which prepared in the same condition.P（F-TH:EDOT）-1/1 also shows better electrochromism than PEDOT performance when the 0.1 mol?L^-1Li Cl O₄/CH₃CN electrolyte was replaced by a high-boiling electrolyte 0.1 mol?L^-1Li Cl O₄/PC.Therefore,the new electrochromic films prepared via electrochemical copolymerization of3-（N-trifluoroacetamido）thiophene and EDOT not only had good performance,but we also found that the electrochromic properties of the film was enhanced through improving the wetting performance of the film electrode to the electrolyte solution.This discovery may provide a new idea for synthesizing electrochromic materials with excellent properties.