DETERMINATION OF REACTIVITY RATIOS FOR THE ANIONIC COPOLYMERIZATION OF ETHYLENE-OXIDE AND PROPYLENE-OXIDE IN BULK

Reactivity ratios have been determined for the anionic copolymerization of ethylene oxide and propylene oxide in bulk over the temperature range 0-80-degrees-C. The ratios were obtained by two methods, the first using the variation of copolymer composition with monomer feed composition according to the Mayo-Lewis equation, and the second using the triad sequence distribution derived from C-13-NMR spectra. In both methods, the ratios were obtained by a computer search for the values giving the best fit between simulated and experimental data. The program took composition drift into account by numerical simulation of the copolymerization as a series of small steps, the feed composition being adjusted after each step. The reactivity ratios were independent of temperature within experimental error, with average values r(E) = 2.8 +/- 0.6 and r(P) = 0.25 +/- 0.07 from the Lewis-Mayo equation, and r(E) = 3.1 +/- 0.4 and r(P) = 0.30 +/- 0.04 from the triad distribution.