Research in the Chemistry of Carbazole Derivatives

88. Polymerization of 3-nitro-9-vinylcarbazole

V. M. Sutyagin, V. P. Lopatinskii, E. E. Sirotkina
(Presented by the Scientific-Methodological Seminar of the Organic Departments and Laboratories)

It was shown earlier that 3-nitro-9-vinylcarbazole (3-nitro-9-VK) does not polymerize in the presence of radical-type initiators (benzoyl peroxide, tert-butyl peroxide) [1]. In this connection, it is of definite interest to examine the possibility of synthesizing poly-3-nitro-9-VK using ionic-type catalysts.

The present communication gives the results of polymerization of the indicated monomer in benzene and dichloroethane (DCE) under the action of stannic chloride at \(25^\circ\).

Experimental Part

Characterization of the starting substances

3-Nitro-9-VK was synthesized according to the procedure of [2], with a double-bond content of more than 99.8%; the final product had \(T_{\mathrm{m}} = 112.5\text{–}113^\circ\).

Benzene was distilled over metallic sodium, and the fraction boiling at \(80.2^\circ\) (760 mm Hg) was collected.

Dichloroethane was treated with sulfuric acid, dried with calcium chloride, and distilled over \(P_2O_5\), \(T_{\mathrm{bp}} = 83.7^\circ\).

Stannic chloride of “chemically pure” grade was used in the form of its solution in benzene and DCE.

Polymerization procedure [3]

Into a three-necked round-bottom flask of 50 ml capacity, placed in a thermostat adjusted to the required temperature and equipped with calcium chloride tubes and a stirrer, were successively charg-

the monomer and solvent were charged. After thermostating (10 minutes), the catalyst solution was introduced with a syringe.

The reaction was stopped by adding ethanol to the reaction mixture (in a solvent–ethanol ratio of 1:1.5), after which the polymer was filtered off, dried to constant weight in a vacuum oven, and the product yield was determined.

Viscosity measurements of poly-3-nitro-9-VC were carried out in cyclohexane solution at \(25^\circ\).

Discussion of Results

The dependence of the yield and characteristic viscosity of poly-3-nitro-9-VC on the reaction duration, the concentration of stannic chloride, and the nature of the solvent was studied. The experimental data are presented in Figs. 1, 2, and 3.

Fig. 1. Dependence of the polymerization rate of 3-nitro-9-VC on the reaction duration in benzene solution at \(25^\circ\mathrm{C}\).

(concentrations: monomer—0.084 mol/L, stannic chloride—\(1.73 \cdot 10^{-3}\) mol/L).

As can be seen from Fig. 1, the overall polymerization rate increases with increasing process duration. The conditional molecular weight also increases in this case (Fig. 3).

Fig. 2. Effect of stannic chloride concentration on the yield of poly-3-nitro-9-VC:
1—dichloroethane, 2—benzene.

Fig. 3. Dependence of the characteristic viscosity of poly-3-nitro-9-VK on the degree of polymerization.

The effect of the concentration of stannic chloride on the polymer yield is shown in Fig. 2, from which it follows that there is a directly proportional relationship between the indicated quantities. At the same time, attention is drawn to the fact that the yield of poly-3-nitro-9-VK in a DCE solution is higher than in benzene for the same reaction time.

The nature of the directly proportional dependence of the polymer yield on the catalyst concentration can be explained on the basis of the assumption that, in the present case, molecular scission of the polymer chains apparently occurs through interaction of their ends, as is confirmed by the results of viscometric measurements. As can be seen from Fig. 3, the conditional molecular weight of the polymer does not depend on the concentration of stannic chloride and is proportional to the degree of polymerization.

For identification of the polymer obtained, elemental analysis was used, and an IR spectrum was also recorded, in which the absorption band characteristic of the vinyl bond of the starting monomer was absent.

Poly-3-nitro-9-vinylcarbazole is a light-yellow powder with \(T_{\text{decomp.}} = 360^\circ\mathrm{C}\) (in a capillary).

The X-ray diffraction pattern of the product, obtained on a URS-50I, had the appearance characteristic of amorphous polymers with diffuse maxima, which indicates slight ordering in the structure of poly-3-nitro-9-VK.

CONCLUSIONS

The dependence of the yield and characteristic viscosity

poly-3-nitro-9-vinylcarbazole on the reaction time, the concentration of tin chloride, and the nature of the solvent at 25°C.

REFERENCES

1. V. M. Sutyagin. Author’s abstract of a Candidate’s dissertation. Irkutsk, 1970.

2. V. P. Lopatinskii, Yu. P. Shekhirev, V. M. Sutyagin. 3-Nitro-9-vinylcarbazole. Methods for the Preparation of Chemical Reagents and Preparations, issue 22, Moscow, IREA, 1970.

3. V. M. Sutyagin, V. P. Lopatinskii, Yu. P. Shekhirev, E. E. Sirotkina. Method for obtaining polymers of 3-substituted 9-vinylcarbazoles. Author’s certificate No. 260172, 1969.