Abstract
4-Vinylpyridine (V) was copolymerized with styrene (S) in benzene solution. The reactions were carried out at 50°C, using 2,2′-azobis(isobutyronitrile) as free radical initiator. Molar feed ratios from 10 to 90% V or S were used. The copolymer compositions were determined from 100 MHz 1H-NMR and 25 MHz 13C-NMR spectra. Data plotted according to the Kelen-Tüdős method indicate that the terminal-unit copolymerization model is strictly applicable to this system. The corresponding reactivity ratios were: r s = 0.75 ± 0.03 and r s = 0.57 ± 0.03. Both the C 1 and C 4 quaternary aromatic carbon resonance of the S and V residues respectively show triad sequence effect. At 25 MHz, the low spectral resolution (particularly for C 1) allows only semi-quantitative determination of V-centered triad fractions. The experimental estimates were in reasonable agreement with the expected values calculated from r v and r s .
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