Carbazole Class Of Conductive Polymer Synthesis, Characterization And Electrically Induced Discoloration Performance Research

Conducting polymers have been considered as promising materials due to their goodelectrochromic properties. Carbazole-containing polymers have various useful propertiessuch as easily forming relatively stable polarons （radical cations）, high charge carriermobility, photochemical stability and electrochromic properties. So it used to beelectrochromic devices, hole transport layer, xerographic printer, microcavity light guide,photovoltaic cells. As an important electrochromic polymer, carbazole-containingpolymers have high conductivity and good redox reversibility; they exhibit high contrastratios and fast switching times in the visible and near-infrared regions. Meanwhile,carbazole-containing compounds have facile structural modification through introducemultifunction substituent, which present various electrochromic properties.In this dissertation, monomers were design synthesized by structural modification,and they were electrochemical synthesized. The electrochromic properties of the resultingpolymers were investigated in detail.1.1,3-Bis（9H-carbazol-9-yl）benzene monomer （BCB） is successfully synthesized byUllmann coupling reaction. Poly（1,3-bis（9H-carbazol-9-yl）benzene）（PBCB） iselectrochemically synthesized and characterized. The PBCB shows fast response time,high outstanding optical contrast （60.98%） and reasonable transparency, with colorchanges from desirable transparent colorless to yellowish green, and then to green color.Electrochromic device （ECD） based on PBCB and poly（3,4-ethylenedioxythiophene）（PEDOT） is also constructed and characterized. PBCB/PEDOT device shows fast responsetime, high optical contrast. Particularly, the device exhibits transmissive blue at neutralstate, good optical memory ability and remarkable stability.2. A donor–acceptor type monomer4,7-dicarbazol-9-yl-2,1,3-benzothiadiazole（CBTD） was synthesized by modified Ullmann coupling reaction and its correspondingpolymer （PCBTD） was obtained via electrochemical polymerization. The polymerdisplayed multiple colors changed from yellow to yellowish green, green, and turquoise blue with the applied potential. Further, electrochemical and optical band gaps wereobtained by using their oxidation and reduction onset potentials and absorption edges,respectively. The optical contrasts of the PCBTD film were found to be28.1%and49.9%at420nm and800nm in the visible region, respectively. The electrochromic deviceconstructed utilizing PCBTD showed high optical contrast, fast response time, and highcoloration efficiency (1728cm²C^–1).3. A star-shaped monomer tris[4-（3,4-ethylenedioxythiophene）phenyl]amine （TEPA）was successfully synthesized and electrochemically polymerized to obtain amultielectrochromic polymer （PTEPA）. The electroactive yellowish green color filmconverted to green, blue and steel blue in turn upon applied stepwise oxidations. TheUV–vis spectra showed that the dedoped polymer film has two absorption bands located at448and686nm, respectively, and the optical band gap was calculated to be1.3eV.Maximum contrast and response time of the PTEPA film were measured. This ECD basedon PTEPA was found to have a neutral green state, good switching times, reasonablecontrast, satisfactory optical memories and redox stability.4. Two bis（ethylenedioxythiophene）naphthalene monomers1,4-bis（2-（3,4-ethylenedioxythiophene））-naphthalene （M1） and2,6-bis（2-（3,4-ethylenedioxythiophene））-naphthalene （M2） were synthesized, andcorresponding polymer P1and P2were electrochemically synthesized and characterized.Based on the detailed studies of the electrochromic properties of two polymers, thepositional substitution effects on the polymers were also discussed. The results of thisstudy showed that the position of substitution can help manipulate the effectiveconjugation length of the polymers, which provided an effective way to tailor the spectralcharacteristics and improve the electrochromic properties of the polymers. Besides, thecorresponding dual type electrochromic devices were constructed and characterized.5. A new multielectrochromic copolymer of1,4-bis（2-thienyl）-naphthalene withbithiophene is successfully synthesized by electrochemical oxidation of their monomersmixture in0.2M NaClO4/ACN solution. Cyclic voltammetry （CV）, UV–vis and FT-IRanalyzes confirm that the resultant polymer is a copolymer rather than a blend or a composite of the respective homopolymers. According to the spectroelectrochemicalanalyzes, the copolymer film reveals distinct electrochromic properties from that of the1,4-bis（2-thienyl）-naphthalene homopolymer film and shows five different colors （yellow,yellowish green, green, greenish blue and blue） under various potentials. Maximumcontrast and response time of the copolymer film are measured as32.7%and0.59s at750nm. The dual-type electrochromic device （ECD） based on P（BTN-co-BT） and PEDOT isalso constructed and characterized in details. This ECD shows a maximum optical contrastof24.2%with a response time of0.32s at780nm. These properties make P（BTN-co-BT）a good candidate for potential commercial applications.