A Novel Ring-Structured Diphenoquione Based on Calix[4]arene as Electron Transport Material Doped in OPC and Its Performances

Abstract

Two ring-structured diphenoquione derived from the calix[4]arene derivative, i.e. 26,28-dipropoxylate-5,17-bi(m,m'-dimethyl)calix[4] diphenoquione (2a) and 26,28-dipropoxylate-5,17-bi(m,m'-diisopropyl)calix[4] diphenoquione (2b) were synthesized. For compounds 2a and 2b, diphenoquinone was used as electron transport moiety and chemically introduced onto calix[4]arene, which provided a rigid and low freedom aligning base for the electron transport moiety. Experiments results revealed that compound 2b which has isopropyl group exhibited better properties compared with 2a which has methyl groups. Compound 2b was of good solubility in common organic solvents and excellent compatibility with polymers such as PC (a polycarbonate) and Vylon200 (a polyester), and could be doped into the polymers at high concentrations, e.g. over 40 wt.%. Single-layered organic photoconductor (OPC) devices were made with compound 2b, 4-(diethylamino)-benzadehyde-1,1-diphenylhydrazone (DEH), Y-type titanium oxide phthalocanine and PC (or Vylon200), which acted as the electron transport material (ETM), the hole transport material (HTM), the charge generation material (CGM) and the bind polymer, respectively. A home-made device, EMS'93, was used to investigate the photoconductivties of the device. Generally, PC was better than Vylon200 as the bind polymer for the OPC devices because the former could make the device have lower and balanced half decay exposures between positive and negative polarities. Investigations also indicated that the half decay exposure of the single-layered OPC devices was strongly dependent on the concentration of the doped ETM, especially at a relatively low concentration, e.g. below 10 wt%. ETM 2b had comparable photoconductities to 3,5-dimethyl-3',5'-isopropyldiphenoquione (MPDQ), a single diphenoquione-structured compound, and 2, 4, 7-trinitro-9-fluorenone (TNF), a traditionally used ETM. The optimal doping concentration of the ring-structured ETM 2b was in the range 15-25 wt.% in PC, while that for MPDQ and TNF, the optimal doping concentration was higher, ranging from 25 wt.% to 30 wt.%. These indicated that the ring-structured ETM 2b have good xerographic properties at low concentrations.