PROCEEDINGS
OF THE TOMSK POLYTECHNIC INSTITUTE NAMED AFTER S. M. KIROV,
ORDER OF THE OCTOBER REVOLUTION AND ORDER OF THE RED BANNER OF LABOR

Vol. 300 1977

RESEARCH IN THE FIELD OF CARBAZOLE CHEMISTRY

103. POLYMERIZATION OF 3-CHLORO-9-VINYLCARBAZOLE

V. M. Sutyagin, V. P. Lopatinskii, E. E. Sirotkina, A. V. Khakhalin

(Presented by the scientific-methodological seminar of the organic departments
of the Faculty of Chemical Technology)

It was previously established by us that 3-chloro-9-vinylcarbazole (3-Cl-9-VC) is readily polymerized in bulk, suspension, emulsion, and solution under the action of radical initiators [1] and ionic-type catalysts [2]. In the present work, the kinetics of polymerization of the monomer in benzene solution in the presence of azobisisobutyronitrile (AIBN) was studied, and its polymerization in benzene solution under the action of stannic chloride as catalyst is also described.

Experimental Part

Characteristics of the Starting Substances

3-Chloro-9-vinylcarbazole was obtained by the method of [3], with m.p. 69° and an unsaturated-content value of 99.9% [4].

AIBN was recrystallized twice from ethanol and dried in vacuum (m.p. 104°).

Benzene was distilled over metallic sodium; it had b.p. 80.2°/760 mm Hg.

Dichloroethane (DCE) was treated with sulfuric acid, dried with calcium chloride, and distilled over phosphorus pentoxide, b.p. 83.7°/760 mm Hg.

Stannic chloride of “chemically pure” grade was used.

The polymerization kinetics was studied dilatometrically according to the method of [5]. The reaction rate was determined from the slope of the straight line expressing the dependence of monomer conversion on the duration of the process.

Polymerization of 3-Cl-9-VC in Solution under the Action of Stannic Chloride

Into a three-necked round-bottom flask equipped with a stirrer with a seal and calcium chloride tubes, weighed amounts of the monomer and solvent were charged successively. The flask was placed in a thermostat adjusted to the specified temperature. After 15 min of thermostating, the calculated amount of stannic chloride was added to the reaction mixture in the form of a 0.8% solution in benzene. At specified time intervals, the polymers obtained were precipitated

with ethanol, the precipitate was transferred to preweighed filters, washed with fresh portions of alcohol, dried in vacuo to constant weight, and then the polymer yield was determined.

Viscometric measurements of the polymers were carried out in an Ubbelohde viscometer in benzene and DCE solution at \(25 \pm 0.1^\circ\). Polymer concentrations were taken as \(0.1\)—\(0.15\) g per 100 ml of solvent.

Discussion of Results

Figure 1 shows a check of the order of reaction “\(n\)” (determination by the graphical method of the linear function of concentration versus time) for DAC-initiated polymerization of 3-Cl-9-VC in benzene solution at \(60^\circ\). The reaction proceeds according to first order, and the rate constant of the process is described by the equation

\[ K = \frac{2.303}{\tau}\lg \frac{100}{100-x}, \]

where \(x\) is the degree of conversion of monomer into polymer, %,
\(\tau\) is the reaction time, sec.

The kinetic curves presented in Fig. 2 show that the overall rate of the process increases with increasing concentration of DAC in the system. As follows from Fig. 3, in this case the law of proportionality of the reaction rate to the square root of the DAC concentration is well obeyed.

Fig. 1. Dependence of \(\lg \frac{100}{100-x}\) on time in initiated polymerization of 9-VC at \(60^\circ\)C. \(x\) — conversion, %.

Fig. 2. Kinetics of polymerization of 3-chloro-9-vinylcarbazole in benzene solution at \(60^\circ\)C. Concentrations: monomer — 0.78 mol/l; DAC initiator: 1 — \(9.00 \cdot 10^{-4}\) mol/l; 2 — \(4.65 \cdot 10^{-3}\) mol/l; 3 — \(9.15 \cdot 10^{-3}\) mol/l; 4 — \(1.64 \cdot 10^{-2}\) mol/l.

The order of the reaction with respect to the initiator, determined from the logarithmic dependence of the polymerization rate on the DAC concentration, is 0.5. This value gives grounds to assume bimolecular termination of the polymer chains.

By plotting the dependence of \(\ln K\) on \(1/T\) (Fig. 4), the activation energy of this process was determined; its numerical value is equal to 19.5 kcal/mol.

To determine the value of the ratio of the rate constants for growth \((K_p)\) to termination \((K_0)\) of the polymer chain \((K_p/K_0^{0.5})\), as is known, in addition to measuring the stationary polymerization rate \((W)\), it is necessary

know the magnitude of the initiation rate \((V_{\text{in}})\). \(V_{\text{in}}\) was calculated from the values of the duration of the induction period \((t_{\text{ind}})\) and the inhibitor concentration. Figure 5 shows the course of polymerization of 3-Chloro-9-VC in the presence of benzoquinone at \(75^\circ\), from which it is evident that the magnitude of the induction period is proportional to the concentration of inhibitor introduced into the system.

Fig. 3. Dependence of the polymerization rate of 3-chloro-9-vinylcarbazole on the concentration of AIBN at \(60^\circ\)C.

Fig. 4. Dependence of \(\ln K\) on \(1/T\) for the polymerization of 3-chloro-9-vinylcarbazole. AIBN concentration — \(9.15 \cdot 10^{-3}\) mol/L.

Substituting into the expression for the initiation rate, equal to the relation \(V_{\text{in}} = [x]/t_{\text{ind}}\), (where \([x]\) is the concentration of benzoquinone, mol/L), the values of the induction period found experimentally from Fig. 5, it is easy to calculate \(V_{\text{in}}\). It should be noted here that the ratio \([x]/t_{\text{ind}}\) at different amounts of benzoquinone was constant. This fact indicates a quantitative interaction

Fig. 5. Kinetics of inhibited polymerization of 3-chloro-9-vinylcarbazole in the presence of benzoquinone at \(75^\circ\)C in benzene solution. Benzoquinone concentration: 1 — without inhibitor; 2 — \(1.20 \cdot 10^{-3}\) mol/L; 3 — \(2.40 \cdot 10^{-3}\) mol/L.

Fig. 6. Polymerization of 3-chloro-9-vinylcarbazole in benzene solution at \(25^\circ\)C in the presence of stannic chloride. Monomer concentration — 0.088 mol/L. Stannic chloride concentration: 1 — \(7.70 \cdot 10^{-6}\) mol/L; 2 — \(19.25 \cdot 10^{-6}\) mol/L; 3 — DCE solvent; stannic chloride concentration \(19.25 \cdot 10^{-6}\) mol/L.

the interaction of reaction chains with the inhibitor and the absence of interaction of polymer radicals with one another.

Thus, substituting the known quantities into the equation \(K_p/K_0^{0.5}=W/V_{\text{in}}^{0.5}[M]\), we obtain a value equal to \(14.6 \cdot 10^{-2}\ \text{l}^{0.5}\ \text{mol}^{-0.5}\ \text{s}^{-0.5}\).

The initiation efficiency \((f)\) was calculated from the equation

\[ f = V_{\text{in}}/2K_{\text{dec}}\cdot C, \]

where \(C\) is the initiator concentration, mol/l;
\(K_{\text{dec}}\) is the rate constant of DAC decomposition, s\(^{-1}\).

If the value \(K_{\text{dec}} = 1.2 \cdot 10^{-4}\) (Arnett’s data [6]) is used, then we obtain \(f\) equal to 0.45.

The polymerization of 3-Cl-9-VC in benzene solution in the presence of stannic chloride at 25° was studied. The degree of conversion was judged from the polymer yield and from the monomer conversion. In particular, monomer conversion was determined from the amount of free 3-Cl-9-VC by the method of addition of mercury acetate [4]. The difference between polymer yield and monomer conversion did not exceed 1%.

Figure 6 shows the course of the polymerization process of 3-Cl-9-VC in benzene solution at 25° for various amounts of stannic chloride. As is seen from Fig. 7, with increasing catalyst concentration the polymer yield increases and represents a proportional dependence for

Fig. 7. Dependence of the yield of poly-3-chloro-9-vinylcarbazole on the concentration of stannic chloride at 25°C.
Monomer concentration — 0.088 mol/l.
Reaction time:
1 — 1 min; 2 — 3 min.

Fig. 8. Dependence of the intrinsic viscosity of poly-3-chloro-9-vinylcarbazole on monomer conversion at different concentrations of stannic chloride: X — \(7.7 \cdot 10^{-6}\) mol/l; \(|\cdot|\) — \(19.25 \cdot 10^{-6}\) mol/l; \(\odot\) — \(38.5 \cdot 10^{-6}\) mol/l.

a certain time interval (1–5 min), where this dependence is linear. Such a character of the curve can be explained on the basis of the assumption that, in the present case, monomolecular chain termination occurs through interaction of its ends, which is confirmed by the results of viscometric studies. As is seen, for example, from Fig. 8, the conditional molecular weight of poly-3-chloro-9-vinylcarbazole does not depend on the catalyst concentration and is proportional to the degree of polymerization.

Figure 6 presents comparative data on the polymerization of 3-Cl-9-VC in benzene and DCE, from which it is seen that the polymer yield in DCE solution is higher (all other conditions being equal) than in benzene. It should be noted that the values of the intrinsic viscosity of the polymers.

obtained in DCE were higher than the corresponding values for the indicated substance synthesized in a solution of benzene and carbon tetrachloride.

The observed dependence of the total reaction rate and the intrinsic viscosity of the polymers on the nature of the solvent can be explained by the assumption that the formation of carbonium ions is considerably accelerated when solvents with high dielectric permittivity are used, and this, apparently, is the reason for the increase in the polymerization rate.

Conclusions

1. The kinetics of polymerization of 3-chloro-9-vinylcarbazole in benzene solution in the presence of dinitrile of azobisisobutyric acid was studied by the dilatometric method; the ratio \(K_p/K_0^{0.5}\), the initiation rate, the activation energy, and the reaction orders with respect to monomer and initiator were determined.

2. The polymerization of 3-chloro-9-vinylcarbazole in benzene and dichloroethane solution in the presence of stannic chloride at 25° was studied, and it was established that the polymer yield increases with increasing catalyst concentration and that the intrinsic viscosity of the polymers is proportional to the degree of polymerization and does not depend on the concentration of stannic chloride.

References

1. V. M. Sutyagin, V. P. Lopatinskii, Yu. P. Shekhirev, A. S. Smirnov, G. A. Kineva, A. P. Bychkova. Method for obtaining polymers. Author’s certificate 224065 (1968).

2. B. M. Sutyagin, V. P. Lopatinskii, E. E. Sirotkina, Yu. P. Shekhirev. Method for obtaining polymers of 3-substituted 9-vinylcarbazoles. Author’s certificate 260172 (1969). BI, No. 25, 1968.

3. V. P. Lopatinskii, Yu. P. Shekhirev, V. M. Sutyagin, A. P. Bychkova, Methods for obtaining chemical reagents and preparations. Issue 22. Moscow, IREA, 1970.

4. R. W. Martin. Analyt. chem., 21, No. 2, 921 (1949).

5. G. P. Gladyshev. Polymerization of Vinyl Monomers. Alma-Ata, Publishing House of the Academy of Sciences of the Kazakh SSR, 1964.

6. L. Arnett. J. Am. Chem. Soc., 74, 2027 (1952).