Abstract
AbstractThe Stereoregularity of polystyrenes prepared with radical, anionic, and cationic initiators was determined by means of 13C‐NMR spectroscopy. Aromatic C1 carbon spectra measured on o‐dichlorobenzene solutions consisted of about six peaks and the peak at the highest magnetic field (at 146,3 ppm) was assigned to an rrrr pentad. The proportion of racemic dyads Pr, was directly calculated from the proportion of the rrrr pentad peak assuming that the Bernoullian statistics holds for the polymerization of styrene. The Pr values of polystyrenes prepared with radical initiators at temperatures from 80° to 0°C were 0,72–0,73, while the cationic polymerizations gave Pr values ranging from 0,54 to 0,68. The Pr values of the same polystyrenes were also calculated by use of a p‐xylene/chloroform mixture as solvent for the 13C‐NMR measurements. For anionically obtained polystyrenes, considerably different Pr values were found using both solvent systems. From this, it was considered that the anionic polymerization of styrene with butyllithium as catalyst does not obey the Bernoullian statistics.
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