I. Miyamoto et al., STUDIES ON STRUCTURE OF CUPRAMMONIUM CELLULOSE .3. STRUCTURE OF REGENERATED CELLULOSE TREATED BY CUPRAMMONIUM SOLUTION, Polymer Journal, 28(3), 1996, pp. 276-281
An attempt was made to clarify the supermolecular structure of regener
ated celluloses recovered from the copper-absorbing celluloses, which
were prepared by treating solid cellulose with aqueous (ag) cuprammoni
um hydroxide (CAH) solutions having different hydroxyl ion content (C-
OH). X-Ray diffraction and CP/MAS C-13 NMR analyses carried out on the
regenerated cellulose samples revealed that the samples had a wide va
riation of supermolecular structures depending on the C-OH: (1) The CA
H solutions with C-OH<0.174 mol l(-1) brought about the increase in cr
ystallinity, crystalline size and intramolecular hydrogen bond formati
on, and (2) the CAH solutions with C-OH>0.479 mol l(-1) tend to give t
he reverse results. Circular dichroism (CD) spectra for the cellulose
films treated by two kinds cuprammonium solutions with C-OH<0.174 and
C-OH>0.479 revealed that cuprammonium ions orderly coordinate to C-2 a
nd C-3 hydroxyl groups of glucopyranose units of cellulose in only amo
rphous region in the case of C-OH<0.174 and the CAH with C-OH>0.479 pe
netrates into even a part of crystalline region of cellulose and cause
s a ligand exchange from ammonia to hydroxyl groups to give a non-diss
ociated complex form of cellulose having certain random cross-linking
by copper atom. Thus, we concluded that the difference in the complex
form of the copper-absorbing cellulose influences considerably the sup
er-molecular structure of the regenerated celluloses.