Homo-and copolymerization of aliphatic cyclic carbonates with suppression of transesterification

The ring-opening polymerization (ROP) of cyclic carbonates initiated with chiral Al-alkoxides that bear stcrically demanding ligands provides sufficient control of molar mass, macromolecular architecture and end groups of the resulting (co)polymers. The present paper reports that this kind of control takes place also in the cyclic carbonates (trimethylene carbonate (TMC) and 2,2-dimethyltrimcthylene carbonate (DTC)) homopolymerization and their copolymcrization with L,L-lactide (LA). This is in contrast to previous, reported attempts of cyclic carbonates polymerization proceeding on the achiral active species. Thus, in the properly chosen conditions di- and mutiblock copolymers could be obtained by starting the polycarbonate blocks growth with the living poly(L,L-lactide) (PLA). Namely, application of a bulky, Schiffs base derivative: (5)-(+)-2,2'-[l,r-binaphtyl- 2,2'diylbis-(nitrylomethilidyne)]-diphenolate at the aluminum alkoxidc active species (SBOiAl-O/Pr) results in a suppression of the segmental exchange involving polycarbonates and PLA blocks and eventually leads to the corresponding well-defined di- and triblock copolymers formation.