Preparation and microstructural analysis of poly(lactic-alt-glycolic acid)

Alternating copolymers of glycolic (G) and lactic (L) acid were prepared by the condensation of the preformed dimers: L(L)G and L(rac)G. By size exclusion chromatography (THF, PS standards), poly(L(L)G) exhibited a molecular weight (M-n) of 15.6 kg mol(-1), with a weight average molecular weight (M-w) of 26.9 kg mol(-1) and a PDI of 1.72. The M-n for poly(L(rac)G) was 9.2 kg mol(-1), with a M-w of 12.9 kg mol(-1) and a PDI of 1.40. The NMR spectra of poly(L(L)G) were consistent with an isotactic microstructure. NMR spectra of the racemic poly(L(rac)G) were consistent with an atactic structure. The methylene region of the H-1 NMR spectrum showed a tetrad level of resolution of the nearby stereochemical relationships, for example, iii. Resonances for other groups in both the H-1 and C-13 NMR spectra gave only a triad level of resolution. (C) 2008 Wiley Periodicals, Inc.