Synthesis And Application Of Novel Organic Conjugated Compounds As Electrochromic Materials And Flame Retardants

Donor-acceptor electrochromic materials have attracted great attention for the past few years due to the tunable band gap by changing the donor group or the acceptor group. There’re many researches about thiophene family in the electrochromic materials because of their suitable band gap, broad absorbance, good environmental and thermal stability.In this dissertation, three organic conjugated compounds with thiophene as electron-donating group and 1,2,3-triazole as electron-accepting group, were synthesized by click reaction:1,4-di(thiophene-2-yl)-1H-[1,2,3]triazole (DTT), 1-(2,2’-bithiophene-5-yl)-4-(thio-phene-2-yl)-1H-[1,2,3]triazole (BTTT) and 1,4-di(2,2’-bithiophene-5-yl)-1H-[1,2,3]triazole (DBTT). In addition, three linear organic organic conjugated compoundsand two star-shape organic conjugated compounds were synthesized:2,2’:5’,2"-terthiophene (3T), 2,2’:5’,2":5",2’"-tetrathiophene (4T),2,2’:5’,2":5",2’":5’",2""-quinque-thiophene (5T), l,3,5-tri(2’-thien-yl)benzene (3TB), and 1,3,5-tri[5’,2"-(3",4"-ethylene-dioxy-thineyl)-2’-thienyl)]-4-(3’,4’-ethyl-enedioxythineyl)benz ene(3TB-4EDOT). All the compounds were confirmed and characterized by mass spectra (MS/HRMS), nuclear magnetic resonance (1H NMR/13C NMR) and infrared spectrum (FT-IR), and their molecular structures were shown as below:The basic optical and electrical properties of all the compounds were investigated by UV-Vis absorption spectra, fluorescence spectra and electrochemical workstation, including the electronic absorption spectra, the low-energy absorption edge(λedge), redox couple peaks, the emission spectra. In addition, the HOMO/LUMO levels, electrochemical gap, optical band gap and fluorescence quantum efficiency were calculated. And the relation between the molecular structure and the photo-electric properties were also studied. The result showed that the band gap would be decreased with the increase of the conjugated chain. Based on these properties, the application of the organic conjugated compoundsas organic electrochromic materials was also investigated.Two kinds of electrochromic devices were fabricated. The structures of devices:(A) ITO/electrochromic active layer/electrolyte solution/Pt; (B) ITO/electrochromic active layer/gel electrolyte/ITO.Based on the device (A), the electrochromic properties of DTT、BTTT、DBTT、3T、 3TB and 3TB-4EDOT were investigated, and the possible electrochromic mechanism were discussed. The results showed all the conjugated compounds’solid films had electrochromic behaviors.3TBsolid films based on device (A) showed reversible, clear color change from colorless to light gray-blue on electrochemical doping and dedoping.The own colors of DTT、BTTT、DBTT、3T and 3TB-4EDOT solid films were colorless, colorless, yellow, colorless and light yellow,respectively. The DTT、BTTT、DBTT、3T and 3TB-4EDOT solid films exhibited irreversible color change from own colors to light yellow, gray-green, yellow-green, blue and blue on electrochemical doping, respectively. These processes of color change were irreversible. That is to say, on electrochemical dedoping, the color of the organic conjugated compounds’solid film couldn’t change to their own color. The reason may be thatDTT、BTTT、DBTT、3T and 3TB-4EDOT didn’t have substituent group on α- position of thiophene, they were electropolymerized on electrochemical doping firstly, and produced polymers, poly(DTT), poly(BTTT), poly(DBTT), poly(3T) and poly(3TB-4EDOT).The own color of poly(DTT), poly(BTTT), poly(DBTT), poly(3T) and poly(3TB-4EDOT) solid films werelight yellow, yellow, orange, red and yellow,respectively. On electrochemical doping, poly(DTT) didn’t show color change while polv(BTTT), poly(DBTT), poly(3T) and poly(3TB-4EDOT) solid films exhibited color change from their own color to gray-green, yellow-green, blue and deep blue, respectively. While the voltages were removed, the color of the conjugated compounds’solid films changed to their own color. That’s to say, poly(DTT), poly(BTTT), poly(DBTT), poly(3T) and poly(3TB-4EDOT) solid films had reversible electrochromic properties. Poly(DTT), poly(BTTT), poly(DBTT), poly(3T) and poly(3TB-4EDOT) solid films based on device (B) also showed reversible, clear color change, which were similar to that of device(A).Polymer materials have played a significant role in the national economy and people’s lives, but general polymer materials are flammable, prone to fire accidents, which is a huge threat to human lives and property.Halogen flame retardant and phosphorus-containing flame retardant have been widely used in our life, but their toxicity limits their development.Therefore, developing novel organic flame retardant is an important research issue.Boron-containing flame retardants have been focused because of their nontoxic, smoke restrained and high-efficiency properties.So it’s significant to develop novel organic boron-containing flame retardant.In this dissertation, an aryl boronic acid 3(4,4’,4"-three boric acid-phenyl)amine(3BzN-3B) was synthesized and added to epoxy resin with magnesium hydrate (Mg(OH)2). And the flame retardant property of the modified epoxy resin was investigated by thermogravimetric analysis, vertical burning test,conecalorimetrytest and scanning electron microscope. The result showed that the char residue rate of EP/5%3BzN-3B/5%Mg(OH)2 was 26.29%, which was higher than that of EP (9.13%) and EP/10%Mg(OH)2 (21.31%). The limiting oxygen index (LOI) of EP/5%3BzN-3B/35%Mg(OH)2 was 31.9% and EP/5%3BzN-3B/35%Mg(OH)2 achieved a UL-94 V-0 rating in vertical burning test. However, the LOI of EP/40%Mg(OH)2 was 28.7% and EP/40%Mg(OH)2 failed to meet the level of flame retardant. Thus,3BzN-3B and Mg(OH)2 have good synergistic flame retardant effect. They could not only improve the char residue rate and LOI of EP, but also reduce the total heat release and the total suspended particles of EP.