Influence of urea on methyl $$\upbeta$$-D-glucopyranoside in alkali at different temperatures

Abstract

The dissolution efficiency plays an important role on the properties of regenerated cellulose-based products. Urea is known to be one of the additives aiding to improve cellulose dissolution in the NaOH(aq) system. The acting mechanism caused by urea has been debated and one of the hypothesis is that urea could induce a conformational change on cellulose, which promotes dissolution. Here we used NMR spectroscopy on a model system for cellulose, namely, methyl $$\upbeta$$β-D-glucopyranoside ($$\upbeta$$β-MeO-Glcp) and compared chemical shifts and J couplings, which both are indicators for conformational changes, as a function of temperature and upon the addition of urea. We found that in NaOH(aq), the hydroxymethyl group changes its conformation in favour of the population of the gt rotamer, while the presence of urea induced temperature dependent conformational changes. Heteronuclear Overhauser effect experiments showed that urea associates with cellulose but in a non-specific manner. This suggests that urea rather than binding to the carbohydrate, changes the chemical environment inducing a change in conformation of $$\upbeta$$β-MeO-Glcp and likely also for cellulose when dissolved in NaOH(aq) with urea.

Formulation Development and in Vitro Characterization of Ternary Hydrotropic Solid Dispersions of Aceclofenac

“…Urea is reported to promote reduction in crystallinity and to accumulate on hydrophobic surfaces of drug particles, thereby weakening interactions between hydrophobic particles [53][54][55][56]. Urea may have impacted entropy and shifted the dissolution equilibrium of ACF in buffer as well as water by interacting favorably with drug and SKM [57]. However, higher proportion of urea as in U3 failed to produce expected enhancement.…”

“…With an aim to achieve still better solubility, superdisintegrant, CP was added in small parts to the binary carrier mixture of SKM and urea. Several studies have reported the use of CP as single carrier component in formulation of SD [34][35][36]57]. Increase in level of CP beyond a threshold value did not produce any further improvement in solubility as observed with C3 and C4, with maximum enhancement being observed with C2 [33][34][35].…”

‘Lignin and extractives first’ conversion of lignocellulosic residual streams using UV light from LEDs

“…34 Aldehydes are present in the region between 9 and 11 ppm, highlighted in green. The spectra lack features of celluloses and hemicelluloses which are usually found between 2.5-5.5 ppm 35,36 indicating that neither cellulose nor hemicellulose was extracted using MeCN at room temperature (Fig. 5a).…”