USE OF CROWN-ETHER IN THE ANIONIC-POLYMERIZATION OF PROPYLENE-OXIDE .2. MOLECULAR-WEIGHT AND MOLECULAR-WEIGHT DISTRIBUTION

The production of unsaturation by hydrogen abstraction from monomer (transfer reaction) during the polymerization of bulk propylene oxide catalysed by potassium alkoxide in the presence of 18-crown-6 ether was assessed by NMR spectroscopy. Chain transfer constants were measured as a function of the ratio of crown ether to potassium ion (r = 0-4.5) over a range of temperatures (T = 20-80-degrees). Conditions were defined for the preparation of monofunctional poly(oxypropylene) of moderate chain length (about 200 P units, M(n)BAR > 10,000) and narrow chain-length distribution (M(w)BAR/M(n)BAR approximately 1.2).