Lignocellulose fibers elaborating super-swollen three-dimensional cellulose hydrogels from solution in N,N-dimethylacetamide/lithium chloride

Abstract

Super-swollen hydrogels were prepared in vitro from lignocelluloses of various origins via direct dissolving in N,N-dimethylacetamide/lithium chloride (DMAc/LiCl) followed by regeneration from solutions. The hydrogels retained a large amount of water (up to 2500 wt%) and had high porosity and specific surface areas. Superabsorbance of the hydrogels was confirmed with a wide angle X-ray scattering method. The hydrogels seem to be smart matters due to PH-dependent behavior by swelling and pH change experiments. The gelation mechanism includes spontaneous self-assembly from the solutions in DMAc/LiCl, due to the reconstruction of new hydrogen bond webs between lignocellulose chains and water. The hydrogels exhibited high stability but their morphology changed while drying due to water removal and the collapse of the H-bonds.

Comparative Study of Powder Celluloses and Cellulose Hydrogels by Waxs Method. Impact of Measurement Technique and Computation on Variability of Results

“…For the hydrogel prepared from hardwood pulp powder, these parameters were 97.4 mass% and 2800 mass%, respectively. 25 Monitoring the long-term stability of the hydrogels showed that they maintained a stable 3D structure without collapsing when stored in water and ethyl alcohol at the temperature ranging from 20 °C to 70 °C during periods from 1 day to 180 days. We concluded on the basis of the results that the super-swollen hydrogels were stable in these media as long as needed because the swelling and absorbing capacity of the hydrogels did not change under these exposure conditions.…”

“…The preparation of the powder celluloses, including the hydrolysis of the pristine samples, the dissolution of the powders in the solutions of DMAc/LiCl and the regeneration from the solutions, was performed as described elsewhere. 25 Shortly, the pulp and the flax fibers were hydrolyzed with a 10 wt% aqueous solution of nitric acid to prepare the powder cellulose samples. The dissolution of cellulosics in DMAc/LiCl strongly required a pretreatment of the samples, which was performed by solvent exchange, by infusing and rinsing the powder celluloses with deionized water and then with DMAc.…”

“…The main physicochemical properties of the obtained hydrogels were studied and described in our earlier publication. 25 To characterize the sustainability of the hydrogels, we investigated their long-term stability while varying time and temperature of storing in water and ethyl alcohol, separately or combined in various proportions, by controlling their transparency depending on the composition of the aqueous solutions. We also monitored the absorbing capacity and swelling values of the hydrogels during storage in the above solutions.…”

“…The hydrogels can retain large amounts of water compared to the pristine cellulose. 7 Out of the studies dedicated to hydrogels, the majority have been made on those derived from bacterial cellulose, due to the peculiarities of the synthesis and shape. 8 In recent years, plant-derived cellulose has come to be also widely applied to prepare hydrogels.…”

“…8 In recent years, plant-derived cellulose has come to be also widely applied to prepare hydrogels. 7,[9][10][11] The unique properties of hydrogels, namely, their high water-holding and absorption capacity, as well as sufficiently high stiffness, were actively studied by various physical methods. 12,13 Some major aspects concerning hydrogels have been considered in numerous publications, including a number of reviews (see for instance 14 ).…”