Alcohol-initiated and SnOct2-catalyzed Ring-Opening Polymerization (ROP) of l-lactide in solution: A re-investigation

[Display omitted] •In contrast to literature neat tin octanoate (SnOct2) is active as catalyst in Ring-opening polymerization (ROP) even at 70 °C.•At this temperature it yields CHOH and COOH terminated linear chains.•However, at 115 °C or higher neat SnOct2 yields cyclic polylactides. Alcohol-initiated ring-opening polymerizations (ROP) of l-lactide (LA) were studied in solution at 70 °C, whereupon the nature of the alcohol, the LA/initiator ratio, the LA/SnOct2 ratio and the time were varied. In contrast to literature, neat SnOct2 is catalytically active in THF and several aromatic but donor solvents, such as 1,3-dioxolane, dimethylformamide (DMF) or N-methyl pyrrolidone (NMP), strongly reduce the activity of SnOct2. In agreement with literature, no cycles were formed by neat SnOct2 at 70 °C in toluene, whereas almost complete cyclization occurs at 115 °C. This finding is attributed to strongly reduced mobility of the initially formed linear chains having one sn-O-CH and one anhydride end group. Due to better solvation and enhanced mobility cyclization occurs in THF at 70 °C.