, Volume 9, Issue 6-7, pp 276-283

New polymer syntheses

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L-Lactic acid O-carboxyanhydride (L-Lac-OCA) was prepared by phosgenation of L-lactic acid lithium salt. Its polymerization was conducted using a variety of initiators, and the resulting poly(L-lactides) were characterized by 1H-and 13C-NMR spectra, by vapor pressure osmometry (VPO) and by optical rotation. Number average molecular weights > 3 000 were never obtained. Also polymerizations of D,L-Lac-OCA did not give higher Mn's. The formation of isotactic triads was favored under all conditions. Furthermore, copolymerizations of L-Lac-OCA and various α-amino acid N-carboxyanhydrides (NCAs) only yielded low molecular weight poly(depsipeptides). The polymerization mechanism is discussed.

We thank the Deutsche Forschungsgemeinschaft for financial support.