The high resolution CP/MAS/DD ~aC 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 ~3C n.m.r, spectra.
Посилання на статтю:
13C n.m.r, observation of poly(L-lactide) in the narrow channels of its inclusion compound with urea / C. Howe, S. Sankar* and A. E. Tonellit // Polymer. – 1993. – Vol 34. – P. 2674-2676.