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 1 H NMR spectrum showed a tetrad level of resolution of the nearby stereochemical relationships, for example, iii . Resonances for other groups in both the 1 H and 13 C NMR spectra gave only a triad level of resolution.