True molecular solutions of natural cellulose in the binary ionic liquid-containing solvent mixtures
2014
Rein, Dmitry M. | Khalfin, Rafail | Szekely, Noemi | Cohen, Yachin
Evidence is presented for the first time of true molecular dissolution of cellulose in binary mixtures of common polar organic solvents with ionic liquid. Cryogenic transmission electron microscopy, small-angle neutron-, X-ray- and static light scattering were used to investigate the structure of cellulose solutions in mixture of dimethyl formamide and 1-ethyl-3-methylimidazolium acetate. Structural information on the dissolved chains (average molecular weight ∼5×104g/mol; gyration radius ∼36nm, persistence length ∼4.5nm), indicate the absence of significant aggregation of the dissolved chains and the calculated value of the second virial coefficient ∼2.45×10–2molml/g2 indicates that this solvent system is a good solvent for cellulose. More facile dissolution of cellulose could be achieved in solvent mixtures that exhibit the highest electrical conductivity. Highly concentrated cellulose solution in pure ionic liquid (27wt.%) prepared according to novel method, utilizing the rapid evaporation of a volatile co-solvent in binary solvent mixtures at superheated conditions, shows insignificant cellulose molecular aggregation.
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