<scp>ROP</scp> of <scp>L?lactide</scp> and <scp>??caprolactone</scp> catalyzed by tin( <scp>ii</scp> ) and tin( <scp>iv</scp> ) acetates–switching from <scp>COOH</scp> terminated linear chains to cycles

The catalytic potential of tin(II)acetate, tin(IV)acetate, dibutyltin-bis-acetate and dioctyl tin-bis-acetate was compared based on polymerizations L-lactide conducted in bulk at 160 or 130°C. With SnAc2 low-Lac/Cat ratios (15/1–50/1) were studied linear chains having one acetate carboxyl end group almost free cyclics obtained. Higher monomer/catalyst lower temperatures favored formation cycles that reached weight average molecular weights (Mw's) between 100,000 2,500,000. SnAc4 yielded mixtures species under all reaction conditions. Dibutyltin- tin bis-acetate cyclic polylactides most conditions with Mw's the range 20,000–80,000. Ring-opening performed ?-caprolactone showed similar trends, but COOH-terminated significantly more to analogous experiments lactide. reactivity catalysts decreased following order: > Bu2SnAc2 ~ Oct2SnAc2.