ANIONIC-POLYMERIZATION OF PROPYLENE-OXIDE - INVESTIGATION OF DOUBLE-BOND AND HEAD-TO-HEAD CONTENT BY NMR-SPECTROSCOPY

Propylene oxide was anionically polymerised in bulk at 80-degree-C und er a range of initial conditions, from zero hydroxyl content to a mole ratio of hydroxyl to potassium catalyst of 10. The double bond conten t of the polymers was measured by H-1 NMR spectroscopy over a wide ran ge of conversions, and values of the transfer constant were determined . The results were fitted to a reaction mechanism involving suppressio n of the transfer reaction by hydrogen bonding of hydroxyl groups to a ctive ion pairs. The head-to-head content of the polymers was measured by C-13 NMR spectroscopy. The overall proportion (approximately 40%) of 'head-to-head' reactions relative to head-to-tail addition was not greatly affected by suppression of the transfer reaction, since an inc rease in the number of head-to-head additions compensated the decrease in proton abstraction from methyl groups via the transfer reaction.