Design,Synthesis And Visualized Application Of Novel Organic Electrochromic/electrofluorochromic Materials

Electrochromism/electrofluorochromism is a phenomenon in which the optical properties(reflection,transmission,absorption/fluorescence emission)undergo a stable,reversible change under an applied electric field,resulting in a reversible change in color or a switching change in fluorescence.This visual optical modulation technique contains both reflection(color)and emission(fluorescence)modulation modes.Organic materials are developing rapidly due to their excellent processing properties,simple molecular design,and low cost.Therefore,the development of organic-based electrochromic/electrofluorochromic materials has become a research hotspot.Traditional organic materials for optical modulation,on the other hand,have certain drawbacks,such as low fluorescence contrast,sluggish reaction speed,poor cycling stability,and a lack of practical application development.The majority of current research is focused on enhancing the performance of such optically modulated materials,whereas research on visualization applications of electrochromic/electrofluorochromic materials is still in its early stages.Therefore,it is urgent to design and develop high-performance electrochromic/electrofluorochromic materials and explore their visualization applications.In this thesis,three types of organic electrochromic/electrofluorochromic materials were synthesized and applied for various applications,including self-indicated supercapacitors,visualized test strips,and self-powered human motion devices.The main contents are divided into three parts as follows:First,a conjugated polymer with a twisted structure containing thiophene and triphenylamine double redox centers and strong electron withdrawing cyano groups was prepared by electrochemical polymerization.The conjugated polymer has a high discharge voltage and efficient charge transport due to the reduced lowest empty orbital(LUMO),twisted polymer arrangement,and fine micro-nano structure.This molecular engineering strategy synergistically improves the electrochromic and electrochemical energy storage properties in a flexible electrochromic supercapacitor,with a high optical contrast of 67%,a voltage window of 2.0 V,a capacitance of 32.9 m F/cm²,and excellent cycling stability(86%capacitance retention and 96%optical modulation retention for 7000 cycles).In addition,a porous network polysiloxane containing oligoaniline and cyanophenethylene groups was synthesized by electrochemistry-assisted hydrolytic cross-linking reactions.The electroactive fluorescent polysiloxane exhibited good electrochromic/electrofluorochromic bifunctional properties,including high optical contrast(52.5%),high fluorescence quenching(85%),and good cycling stability.Subsequently,an interleaved symmetric supercapacitor was assembled,whose energy state can be indicated synergistically by color switching from light yellow-green to dark green and a fluorescent"on and off".This energy visualization supercapacitor integrates energy storage and color/fluorescence dual-function modulation for the first time.Secondly,a novel electroactive fluorescent poly(urea-urethane)was designed and synthesized by a terpolymerization reaction of oligoaniline,tetraphenylene group,and alkyl isocyanate.The polymer possesses electrochromic/electrofluorochromic dual-modulation properties,including high optical contrast(50.4%),significant fluorescence on/off contrast(41.7),and high coloration efficiency(503 cm²/C).This poly(urea-urethane)test strips were prepared in a spraying manner to detect hydrogen peroxide visually.The color changed from light gray to dark-blue while the blue fluorescence changed from"on"to"off"in the concentration range of 0-20 m M for hydrogen peroxide.We further prepared electrospun nanofiber test strips from an electroactive fluorescent poly(amic acid)to visually detect redox substances.The polymer demonstrated good electrochromic and electrofluorochromic properties,such as fast optical(color and fluorescence)response rate and excellent stability(1000 cycles with90%contrast).This test strip was used to detect glucose biomolecules because glucose generates hydrogen peroxide catalyzed by catalase.The test strips showed a change in visible light absorption and fluorescence emission depending on the glucose concentration(0 mmol-20 m M),realizing a dual-mode color/fluorescence visualization.This work opens a new direction for visualizing electrochromic/electrofluorochromic bifunctional materials in chemical detection.Finally,an electroactive fluorescent ionic liquid based on triphenylamine was designed and synthesized.The ionic liquid has good ionic conductivity and stability when assembled into an electrochromic/electrofluorochromic bifunctional device.The device achieves low drive voltage(0.6 V),ultra-fast color response(0.58/0.70 s),fluorescence response(0.57/1.8 s)and high coloring efficiency(786 cm²/C),large color contrast(66.6%),large fluorescence switching contrast(186)and excellent cycling stability(98%contrast after 500 cycles).Then,the bifunctional device is integrated with a PVDF/Ba Ti O₃ piezoelectric nanogenerator to indicate human motion rapidly.The PVDF/Ba Ti O₃ nanogenerator driven by finger-bending could generate enough electrical energy for rapid change of color and fluorescence in the bifunctional device.The results represent an important innovation in the study of visual indication and rapid detection of motion energy.In summary,we have designed and synthesized several novel high-performance electrochromic/electrofluorochromic materials.The visualization studies in supercapacitors,chemical test strips,and integrated piezoelectric nanogenerators provide new application scenarios for future self-indicated electronics.