T. Yamanobe et al., STRUCTURE AND MOBILITY OF POLY(GAMMA-N-ALKYL-L-GLUTAMATE)S IN THE SOLID AND LIQUID-CRYSTALLINE STATES AS STUDIED BY NMR-SPECTROSCOPY, Journal of molecular structure, 295, 1993, pp. 25-37
C-13 CP/MAS NMR and pulse H-1 NMR experiments were carried out for pol
y(gamma-n-alkyl-L-glutamate)s (PALGs) in which the number of carbon at
oms of the alkyl side-chains was either odd or even, in order to eluci
date the conformation, crystal structure and dynamics of the polymers.
From these results, it is found that the main-chain takes an alpha-he
lix conformation irrespective of the alkyl side-chain length. However,
n-alkyl side-chains crystallize with an all-trans zigzag conformation
for PALGs when the number of carbon atoms in the n-alkyl side-chains
is more than 14. Further, from the pulse H-1 NMR results, it is found
that the H-1 spin-spin relaxation time (T2) of the side-chains increas
es abruptly with an increase in temperature for PALGs with a carbon nu
mber of more than 10, which is evidence for the solvent-like nature of
the side-chains in the liquid crystalline phase.