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

Alcohol-initiated ring-opening polymerizations (ROP) of L-lactide (LA) were studied in solution at 70 degrees 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 degrees C in toluene, whereas almost complete cyclization occurs at 115 degrees 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 degrees C.

Automated summary

Alcohol-initiated ring-opening polymerizations of L-lactide were investigated, with variations in the alcohol nature, LA/initiator ratio, LA/SnOct2 ratio, and time. Neat SnOct2 exhibited catalytic activity in THF and some aromatic solvents, while its activity was strongly reduced in solvents like 1,3-dioxolane, dimethylformamide (DMF), and N-methyl pyrrolidone (NMP). The formation of cyclization was observed at 115°C in toluene but not at 70°C, which was attributed to the reduced mobility of the initially formed linear chains in toluene.