Processing of microcrystalline cellulose in dimethyl sulfoxide, urea and supercritical carbon dioxide

Efficient utilization of cellulose in polymer blends is limited because of its high crystallinity. In this work, an attempt to change the inherent crystallinity of cellulose was performed by exposing it to two systems viz. dimethyl sulfoxide (DMSO)–supercritical CO2 and DMSO–urea–supercritical CO2. The cellulose samples processed in DMSO–supercritical CO2 system at 2500 psi, 3500 psi, and 4500 psi showed a reducing trend of the relative crystallinity with increasing pressure. The reduction in the relative crystallinity occurred due to weakening of inter-chain hydrogen bonds in cellulose. The cellulose samples were processed in DMSO–urea–supercritical system at 2500 psi and 4500 psi. A maximum 55% reduction in relative crystallinity was found in the sample that contained 1.80 mol fractions of urea and processed at 2500 psi. This reduction in crystallinity was due to the presence of a DMSO–urea complex, which caused weakening of intermolecular hydrogen bond and an intramolecular hydrogen bond.