Polylactones. XXV. Polymerizations ofracemic-andmeso-D,L-Lactide with Zn, Pb, Sb, and Bi Salts—Stereochemical Aspects

Polymerizations of racemic- and meso-d,l-lactide were conducted at 120°C in xylylene or in bulk. Lead oxide (PbO), zinc stearate, antimony(III) 2-ethylhexanoate, and bismuth(III) 2-ethylhexanoate were used as initiators. With PbO and Zn stearate, bulk polymerizations were also conducted at 150°C. High yields (⩾90%) were only obtained with PbO and Bi(III) 2-ethylhexanoate, but the molecular weights were low in all cases. The stereosequences were analyzed by 1H- and 13C-NMR spectroscopy. A significant stereospecificity was never detected. At higher reaction temperatures the resulting stereosequences show an increasing tendency toward randomness.