Thermal catalytic depolymerization of poly(L-lactic acid) oligomer into LL-lactide: Effects of Al, Ti, Zn and Zr compounds as catalysts

Abstract

A series of Al, Ti, Zn and Zr compounds, i.e., their metal alkoxides, organic acid and enolate salts, halid and oxide, were evaluated as intramolecular transesterification catalysts for the thermal depolymerization reaction of poly(L-lactic acid) oligomer resulting in LL-lactide, meso- lactide and DD-lactide by gas chromatography using a cyclodexstrin chiral stationary phase capillary column. The activity of the intramolecular transesterification compared with that of stannous 2-ethylhexanoate was in the following order: Sn>Zn>Zr>Ti>Al.