Interaction of cellulose with amine oxide solvents
UNSPECIFIED. (2000) Interaction of cellulose with amine oxide solvents. CELLULOSE, 7 (1). pp. 21-33. ISSN 0969-0239Full text not available from this repository.
Cellulose I, mainly as ramie or as Avicel microcrystalline cellulose, has been monitored by optical microscopy and by C-13 CPMAS NMR, over the course of its dissolution in hot N-methylmorpholine N-oxide solvent. Its interaction with the near-solvent N-ethylmorpholine N-oxide and related non-solvents has also been investigated. NMR shows that N-methylmorpholine N-oxide partly converts crystalline cellulose I into amorphous solid cellulose. The changes in chemical shift imply increased flexibility at the glycosidic bonds. In contrast, N-ethylmorpholine N-oxide converts cellulose I to cellulose IIII, without dissolution. Microscopy shows that the ramie fibres swell laterally, and at least some also shorten longitudinally, during dissolution. Model studies using methyl-beta-d-glucopyranose show no evidence from C-13 chemical shifts for different modes of binding with different solvents. However, N-methylmorpholine N-oxide binds more strongly to methyl-beta-d-glucopyranose in DMSO than does N-ethylmorpholine N-oxide, whereas N-ethylmorpholine N-oxide binds better to H2O. Also, C-13 T-1 values for aqueous cellobioside show increasing rotational freedom of the -CH2OH sidechains as N-methylmorpholine N-oxide is added. Together, these observations imply the initial penetration of solvents and near-solvents between the molecular cellulose sheets. Subsequently, N-methylmorpholine N-oxide breaks H-bonds, particularly to O-6, just sufficiently to loosen individual chains and then dissolve the sheets.
|Item Type:||Journal Article|
|Subjects:||T Technology > TS Manufactures
Q Science > QD Chemistry
|Journal or Publication Title:||CELLULOSE|
|Publisher:||KLUWER ACADEMIC PUBL|
|Number of Pages:||13|
|Page Range:||pp. 21-33|
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