ISSN:
0887-624X
Keywords:
ammonia/ammonium thiocyanate solvent
;
cellulose
;
dissolution mechanism
;
solid state CP/MAS 13C-NMR
;
X-ray
;
conformation
;
hydrogen bonding
;
ammonia mercerization
;
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Ammonia/ammonium thiocyanate (NH3/NH4SCN) is an excellent swelling agent and solvent for cellulose, even at a high degree of polymerization. Because polymorphic conversion in cellulose has been a long-standing, perplexing, troublesome problem, we have undertaken to study that mechanism. Solid state CP/MAS 13C-NMR and X-ray analysis proved to be very useful analytical techniques for the task. It appears that during temperature cycling, specific cellulosic inter- and intramolecular hydrogen-bonds are broken as polymorphic conversion proceeds sequentially from the polymorph I to III, and finally at total solvation to amorphous. This proceeds correspondingly via transformation of the polymorph conformations of CH2OH from trans-gauche, “tg,” to gauche-trans, “gt,” to gauche-gauche, “gg.” © 1994 John Wiley & Sons, Inc.
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pola.1994.080320203
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