Research in the Chemistry of Carbazole Derivatives
Abstract Generated abstract
This study examines how anthracene and phenanthrene impurities in carbazole affect the revinylation synthesis of 9-vinylcarbazole oligomers and their electrophotographic properties. Oligomers were prepared from synthetic carbazole with added anthracene, from reagent-grade carbazole, from recrystallized carbazole, and from impurity-enriched purification residues, with product fractions evaluated for yield, charging potential, and photosensitivity. The results indicate that increasing impurity content tends to raise the yield of the low-molecular-weight fraction, consistent with inhibition of further polymerization, while electrophotographic performance remains acceptable up to roughly 8 percent total anthracene and phenanthrene but declines noticeably at higher levels. The work defines a practical purity limit for using reagent-grade carbazole directly in preparing electrophotographic oligomers.
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RESEARCH IN THE CHEMISTRY OF CARBAZOLE DERIVATIVES
68. The Effect of the Purity of Carbazole on the Synthesis and Properties of 9-Vinylcarbazole Oligomers Obtained by the Revinylation Method
E. E. Sirotkina, V. P. Lopatinskii, V. D. Pirogov
(Presented by the scientific-methodological seminar of the CTF)
For a number of years, the Department of TOOS of the Tomsk Polytechnic Institute has been conducting research on the synthesis of 9-vinylcarbazole oligomers by the revinylation method [1]. In the course of synthesis, two fractions are formed, conventionally called the low-molecular-weight fraction (LMF) and the high-molecular-weight fraction (HMF), which possess different physical properties: molecular weight, melting point, electrophotographic and film-forming properties, etc. The LMF includes products with a degree of polymerization of 5–6 ($M.\,w.$ 1000–1200), which have good electrophotographic properties and can be used as a photosensitive layer, for example, in electrophotography. The HMF does not possess such properties. In addition, films made from it crack because of large internal stresses.
For the synthesis of 9-vinylcarbazole oligomers, reagent-grade carbazole from the Kharkov Coke-Chemical Plant, grade “pure,” was used; it was isolated from the anthracene fraction of coal tar and naturally contained various impurities, the chief of which are carbazole companions—anthracene and phenanthrene. Analysis of the reagent-grade carbazole by the procedure of [2] for anthracene and phenanthrene showed (Table 2, item 1) that the total amount of the indicated impurities reaches 5–10% by weight. In addition, the amount of impurities in reagent-grade carbazole changes somewhat from batch to batch.
Therefore, it was of interest to determine the effect of these impurities on the synthesis and electrophotographic properties of 9-vinylcarbazole oligomers.
We investigated the effect of the amount of anthracene in artificial mixtures of it with synthetic carbazole. The synthesis of the oligomers was carried out according to the procedure of [1]. The results of the experiments are presented in Table 1.
The data given show that the addition of anthracene to carbazole up to 10% practically does not lead to a decrease in the electrophotographic properties of the oligomers obtained, whereas the yield of the LMF increases by 10–15%. This indicates an inhibiting effect of anthracene on the polymerization process.
The data on the synthesis of oligomers based on reagent-grade carbazole, carbazole purified by triple recrystallization from acetone, and also carbazole with an increased content of impurities (the carbazole residue obtained when the acetone solution is precipitated after purification of reagent-grade carbazole into water) (Table 2) show that, with an increase in the amount of anthracene and phenanthrene impurities, the ...
Table 1
Effect of anthracene impurity in carbazole on the synthesis and properties of 9-vinylcarbazole oligomers
| Amount of added anthracene, % of total weight | NMF: yield, % of theoretical | NMF: charging potential, volts | NMF: sensitivity, lux·sec·10\(^{-3}\) | VMF: yield, % of theoretical | VMF: charging potential, volts |
|---|---|---|---|---|---|
| — | 45 | 320–380 | 1.4–2.4 | 42 | 140–160* |
| 1.0 | 46 | 300–380 | 1.8–2.4 | 43 | 120–180 |
| 2.0 | 38 | 320–360 | 1.4–2.2 | 48 | 160–200 |
| 5.0 | 53 | 280–320 | 1.4–2.0 | 32 | 130–170 |
| 10.0 | 56 | 280–360 | 1.2–2.2 | 28 | 130–160 |
Note: The tests of electrophotographic properties were carried out using a concentration of the coating solution of 1 g of oligomer per 10 ml of benzene.
* The sensitivity of VMF was not measured because of the low charging potential.
Table 2
Results of experiments on the synthesis of 9-vinylcarbazole oligomers from carbazoles with different impurity contents
| Quality of carbazole | Amount of impurity: anthracene, % | Amount of impurity: phenanthrene, % | Melting point of carbazole, °C | NMF: yield, % of theoretical | NMF: charging potential, volts | NMF: sensitivity, lux·sec·10\(^{-3}\) | VMF: yield, % of theoretical | VMF: charging potential, volts |
|---|---|---|---|---|---|---|---|---|
| Reagent-grade carbazole, series 11, 1966 issue | 1.5–2.0 | 2.6–4.2 | 240–241 | 56 | 280–350 | 1.3–1.8 | 41 | 80–120* |
| Purified carbazole | 0.0–0.1 | 1.9–2.1 | 243.5–245 | 46 | 300–360 | 1.4–1.8 | 50 | 120–160 |
| Residue after purification of reagent-grade carbazole | 6.0–6.8 | 3.0–4.0 | 231–235 | 89 | 120–160 | Not measured | — | — |
Note: * The sensitivity of VMF was not measured because of the low charging potential.
…the yield of NMF increases, while the electrophotographic properties, when the amount of impurities reaches about 8–10%, decrease noticeably.
In this connection, for the synthesis of an electrophotographic oligomer it is possible to use directly only carbazole containing no more than 8% impurity of anthracene and phenanthrene. At a higher impurity content, reagent-grade carbazole must be subjected to additional purification. The electrophotographic characteristics were determined according to known procedures [3].
Conclusions
It has been shown that impurities of anthracene and phenanthrene in the initial carbazole affect the electrophotographic properties and the yield of the target product.
LITERATURE
- V. P. Lopatinsky, E. E. Sirotkina. Izv. TPI, 111, 44 (1961).
- F. P. Lastovsky, Yu. I. Vainshtein. Technical Analysis in the Production of Intermediates and Dyes. Goskhimizdat, Moscow, 1958.
- D. I.-B. Sidaravichyus. Candidate’s dissertation, “Investigation of Certain Organic Polymers of Semiconductor Systems for Electrophotography,” Vilnius—Leningrad, 1967.