A study on the mechanism of dissolution of the cellulose/NH₃/NH₄SCN system. I

Abstract

Abstract Ammonia/ammonium thiocyanate (NH 3 /NH 4 SCN) 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 13 C‐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 CH 2 OH from trans‐gauche, “tg,” to gauche‐trans, “gt,” to gauche‐gauche, “gg.” © 1994 John Wiley & Sons, Inc.