C-13 NMR OBSERVATION OF POLY(L-LACTIDE) IN THE NARROW CHANNELS OF ITS INCLUSION COMPOUND WITH UREA

The high resolution CP/MAS/DD C-13 n.m.r. spectra of bulk, semicrystalline poly(L-lactide) (PLLA) and PLLA confined to the narrow channels of its urea clathrate (PLLA-U) are compared and contrasted to the recently reported CP/MAS/DD spectrum of the crystalline 1:1 stereocomplex (PLLA * PDLA) formed by mixing dilute solutions of PLLA and poly(D-lactide) (PDLA) followed by their cocrystallization. Single resonances are observed for all three carbon types in PLLA-U, while the carbonyl carbons in PLLA * PDLA and all three carbon types in bulk PLLA evidence multiple resonances. Differences in the conformations and packing of PLLA chains in these distinct, ordered solid-state environments are the likely sources of their very different high resolution, solid-state C-13 n.m.r. spectra.