Polylactones, 68: Star-shaped homo- and copolyesters derived from ε-caprolactone, L, L-lactide and trimethylene carbonate

Using Sn(II)2-ethylexanoate (SnOct2) in combination with 1,4-butanediol, 1,1,1-tris(hydroxymethyl)propane (THMP) or pentaerythritol as initiator systems telechelic polyesters or star-shaped homopolyesters of e-caprolactone (e-CL) or L-L-lactide (L-LA) were prepared. These homopolymers were characterized by solution viscosities. 1H NMR and MALDI-TOF mass spectra. Using preformed homopolymers as coinitiators star-shaped polymers having two-block star arms were obtained. Polymerizations of equimolar mixtures of two monomers yielded star-shaped polymers with random copolyesters as star arms. The blockiness or randomness of the star arms was characterized by 13 C NMR spectroscopy. Homo- and copolymerizations of trimethylene carbonate (TMC) were also studied, but they were plagued by intensive side reactions such as formation of cylic oligomers, coinitiation with water and crosslinking via transesterification.