Electropolymerization And Characterization Of Electrochromic Materials Based On Triphenylamine And Thiophene Derivatives

Electrochromic devices (ECDs) have attracted great interest due to their potential use in different applications, elecctrochomic materials have been studied extensively. There are many kinds of electrochromic materials, conducting polymers have attracted a great deal of attention in the electrochromic field because of their outstanding advantages, such as various species, easy preparation, the ease of color control through structure modification etc. Among conducting polymers, polytriphenylamine and polythiophenes derivatives have been to be the focus of research due to their fast switching time, high contrast ratios and soon.It is well-known that introducing donor group at para-triphenylamine can help the good forming polymer of triphenylamine derivatives. Thus the first objective of this dissertation is to design and synthesize two types of monomers containing different donors groups at one of para-triphenylamine, synthesizing two asymmetric monomers containing a plurality of active (4-(9H-carbazol-9-yl)-N,N-diphenylaniline(CDPN) and N,N-diphenyl-4-(thiophen-3-yl)aniline(DPTA)). EDOT exhibit good film-forming and reasonable electrochromic properties. And the electro-copolymerization of CDPN and EDOT (P(CDPN-co-EDOT)), DPTA and EDOT(P(DPTA-co-EDOT)) are successfully achieved. Through electrochemical methods, FTIR spectroscopy and scanning electron microscopy (SEM) analysis, the two resulting polymers were confirmed to be copolymers rather than a blend or a composite of the respective homopolymers. Also scanning electron microscopy (SEM) revealed that the two films surface had accumulated clusters of globules. Besides, the spectroelectrochemical and electrochromic properties of the two copolymer films were investigated. At the neutral state of the copolymer, the π-π*transition absorption peak was located at530nm and the energy gap was calculated as1.77eV (P(CDPN-co-EDOT)) and1.67eV (P(DPTA-co-EDOT)), belonging to be narrow band-gap polymers. P(CDPN-co-EDOT) and (P(DPTA-co-EDOT) also exhibited good electrochromic properties. Spectroelectrochemical analysis revealed that the two copolymer films possessed four and three colors, respectively. At the visible range, both of them showed a maximum optical contrast larger than30%and a switching time1.8s. However, at1100nm the two polymers revealed an optical contrast about50%. It was worth mentioning that the two copolymers possess high coloration efficiency, higher300cm2·C-1.The second objective of this research were to synthesize two functional monomers based on triphenylamine (TPA) core and peripheral thiophene (tris[4-(2-thienyl)phenyl]amine TTPA) or bithiophene groups (4,4’,4"-tris[4-(2-bithienyl)phenyl]amine TBTPA), respectively. The corresponding polymers were prepared by electrochemical oxidative cross-linking. The electrochemical properties of the TTPA and TBTPA, and spectroelectrochemical and electrochromic properties of the PTTPA and PTBTPA were also systematically investigated. TBTPA possessing two thiophene groups exhibited better redox reversibility than that of TTPA. PTTPA and PTBTPA exhibited three different colors under various potentials. Both the polymers showed excellently electrochromic properties with three distinct colors. However, PTBTPA presented the enhanced EC performance with better contrast ratio of44.7%, and PTBTPA showed higher optical contrast (△T) of49%at720nm and52%at1100nm with fast switching response of0.93s (720nm) and0.91s (1100nm) and higher coloration efficiencies of198and285cm2·C-1at720and1100nm, respectively. Scanning electron microscopy (SEM) revealed that the PTTPA and PTBTPA film surface had accumulated clusters of globules, which were smaller than those of PTTPA. The superior performances of PTBTPA suggested its potential as an efficient EC material.