GLOBAL AND INTERNAL MOLECULAR-DYNAMICS OF POLY(ACRYLAMIDE-CO-ALLYL 2-ACETAMIDO-2-DEOXY-D-GLUCOPYRANOSIDE) GLYCOPOLYMERS FROM C-13 NMR RELAXATION STUDIES
R. Roy et al., GLOBAL AND INTERNAL MOLECULAR-DYNAMICS OF POLY(ACRYLAMIDE-CO-ALLYL 2-ACETAMIDO-2-DEOXY-D-GLUCOPYRANOSIDE) GLYCOPOLYMERS FROM C-13 NMR RELAXATION STUDIES, Canadian journal of chemistry, 71(12), 1993, pp. 1995-2006
C-13 spin-lattice and spin-spin relaxation times and nuclear Overhause
r enhancements have been used to examine the molecular dynamics of the
alpha- (1) and beta- (2) anomeric forms of poly(acrylamide-co-allyl 2
-acetamido-2-deoxy-D-glucopyranoside) glycopolymers. The timescale of
motions and the spatial restriction of these motions were determined b
y using various forms of the ''model-free'' approach. It is shown that
the motions of the C-H vectors of the polymer backbone may be describ
ed by a scaled Lorentzian spectral density function, giving rise to an
effective correlation time for overall tumbling. The temperature depe
ndence of this correlation time suggests that the overall motion is de
pendent on viscosity. The overall motion of the polymer molecules is s
hown to be anisotropic in nature by including the spin-spin relaxation
data in the analysis. The N-acetyl methyl and sugar hydroxymethyl (C-
6) groups exhibit internal motions. The activation energies associated
with these internal motions are derived. The difference in relaxation
rates between the alpha and beta anomeric forms, though small, sugges
ts that the motions of the sugar ring may be different for the two sys
tems. This conclusion is supported by potential energy contour map cal
culations, which indicate that the beta anomer (2) has almost twice th
e conformational flexibility of the alpha anomer (1).