Studies on polymerization of N‐vinylcarbazole in the presence of some hydrogen halides

Studies on N-vinylcarbazole polymerization were carried out in the presence of HF, HCl, HBr, and HJ using a variety of solvents. It was found that in the CCl4 solvent, each of the hydrogen halides cause polymerization of N-vinylcarbazole, the obtained polymer including equimolar proportions of hydrogen halide and of N-vinylcarbazole. To determine the influence of solvent polarity, some studies on the polymerization of N-vinylcarbazole influenced by HCl were carried out in the following solvents: carbon tetrachloride, acetone, and methanol. A pronounced contribution of the solvent to the polymerization course was found. A polymerizate including a small proportion of the complex-bonded HCl was obtained when using acetone or methanol solvent. Irrespective of the nature of the solvent used, the appearance of a green color was observed in all instances; hereafter the solution turned brown accompanied by the polymer precipitation. The polymerization proceeds without any disturbances in the presence of some species that capture the radicals, this being evidence for the ionic nature of the mechanism. Based on the UV and ESR spectra analyses, it was found that some change-transfer complexes are formed during polymerization. The result obtained make us accept the following mechanism of N-vinylpolymerization in the presence of hydrogen halides, depending on the reaction medium. Based on the results given, the following conclusions referring to the N-vinylcarbazole polymerization process in the presence of some hydrogen halides can be drawn. In the early stage of polymerization of N-vinylcarbazole, the initiation by means of HX occurs and hereafter the polymer is formed. Then, in a nonpolar medium, a charge-transfer complex of the polymer with hydrogen halide is formed. On the other hand, in a polar medium, this complex cannot be formed.