High-Resolution 13C and 1H Solution NMR Study of Poly(lactide)

High-resolution 500 MHz solution-state 1H and 13C NMR spectra of various poly(lactides) indicate at least hexad stereosequence sensitivity. The poly(lactides) were prepared in vials by melt polymerization of various combinations of l-lactide, d-lactide, and meso-lactide at 180 °C for 3 h using tin(II) bis(2-ethylhexanoate) (tin(II) octoate) as the catalyst in a 1:10 000 ratio. The intensity distribution of the various stereosequence resonances in the NMR spectra indicates a preference for syndiotactic addition during the polymerization process. Minimal evidence of transesterification was observed for these polymerization conditions.