Perichromism: a powerful tool for probing the properties of cellulose and its derivatives.

This overview is concerned with the use of certain dyes (perichromic indicators, hereafter designated as "probes") in order to determine the properties of cellulose, its solutions and solid derivatives. It is arranged as follows: (i) the properties of cellulose and its derivatives that are relevant to their applications are listed; (ii) a general discussion is presented on how perichromism can be employed in order to gain information on the medium where the probe is present; (iii) the results of perichromism, as applied to cellulose, cellulose solutions, and derivative films are discussed.

Hybrid Fe3O4@amino cellulose nanoparticles in organic media--heterogeneous ligands for atom transfer radical polymerizations.

We demonstrate an efficient strategy for the preparation of well-dispersed hybrid particles in organic media via a combination of the solution-based formation of magnetic nanoparticles (MNPs) and subsequent coating with amino celluloses of different degrees of polymerization. The coating process was verified by a combination of light scattering, thermogravimetry, and magnetic techniques. Further, the hybrid particles exhibit an average diameter of roughly 8 nm, as demonstrated by electron microscopy and light scattering. The stability of the so-called MNP@AC(x) hybrid particles (x represents the average degree of polymerization of the amino cellulose) in polar organic solvents such as DMAc was exploited by using the materials as heterogeneous ligands in the atom transfer radical polymerization (ATRP) of styrene. We could show that PS with a near-narrow molecular weight distribution (PDIs<1.3) and low Cu contents (5 ppm) can be prepared. The MNP@AC(x) particles could be separated from the reaction mixture afterwards by an external magnetic field and reused in further polymerizations.

Effect of cellulose physical characteristics, especially the water sorption value, on the efficiency of its hydrolysis catalyzed by free or immobilized cellulase.

Cellulase, an enzymatic complex that synergically promotes the degradation of cellulose to glucose and cellobiose, free or adsorbed onto Si/SiO(2) wafers at 60°C has been employed as catalyst in the hydrolysis of microcrystalline cellulose (Avicel), microcrystalline cellulose pre-treated with hot phosphoric acid (CP), cotton cellulose (CC) and eucalyptus cellulose (EC). The physical characteristics such as index of crystallinity (I(C)), degree of polymerization (DP) and water sorption values were determined for all samples. The largest conversion rates of cellulose into the above-mentioned products using free cellulase were observed for samples with the largest water sorption values; conversion rates showed no correlation with either I(C) or DP of the biopolymer. Cellulose with large water sorption value possesses large pore volumes, hence higher accessibility. The catalytic efficiency of immobilized cellulase could not be correlated with the physical characteristics of cellulose samples. The hydrolysis rates of the same cellulose samples with immobilized cellulase were lower than those by the free enzyme, due to the diffusion barrier (biopolymer chains approaching to the immobilized enzyme) and less effective contact between the enzyme active site and its substrate. Immobilized cellulase, unlike its free counterpart, can be recycled at least six times without loss of catalytic activity, leading to higher overall cellulose conversion.

Application of 1-allyl-3-(1-butyl)imidazolium chloride in the synthesis of cellulose esters: properties of the ionic liquid, and comparison with other solvents.

The ionic liquid (IL), 1-allyl-3-(1-butyl)imidazolium chloride (AlBuImCl), has been synthesized and its properties determined. Increase in the temperature increased its conductivity and decreased its density, polarity, and viscosity. Microcrystalline cellulose (MCC), dissolves in this IL by heating at 80 degrees C; this did not affect its degree of polymerization, decreased its index of crystallinity (Ic), and changed in morphology after regeneration. Convenient acylation of MCC was achieved by using 50% excess anhydride at 80 degrees C, for 24 or 48 h for acetic and butyric anhydride, respectively. The composition of the mixed esters depended on the initial ratio of the anhydrides, and their order of addition.

Applications of ionic liquids in carbohydrate chemistry: a window of opportunities.

Ionic liquids (ILs) are composed only of ions. Of special interest to this review are those where at least one ion (the cation) is organic and whose melting points are below or not far above room temperature. ILs are designated as "green" solvents because they have extremely low vapor pressure, are non-inflammable, and thermally and chemically stable. Therefore, many of them can be, in principle, recycled into the process indefinitely. The objective of the present review is to discuss different aspects of the use of ILs in carbohydrate chemistry, in particular, dissolution and functionalization of simple sugars, cyclodextrins, cellulose, starch, and chitin/chitosan. The molecular structure and synthesis of ILs most frequently employed in carbohydrate chemistry are discussed with an emphasis on imidazolium and pyridinium cations with different counterions. The physicochemical properties of ILs that are relevant to the dissolution and functionalization of carbohydrates, in particular their polarities and hydrogen-bonding abilities, are discussed. Dissolution of simple saccharides and biopolymers in ILs is presented with an emphasis on the mechanism of carbohydrate--IL interactions. Finally, the very interesting novel applications of the solutions obtained are addressed. These include, inter alia, spinning of the dissolved biopolymer into fibers, extrusion into slabs and rods, formation of matrixes for a myriad of substrates, including biomacromolecules, formation of nanocomposites, and functionalization to produce important derivatives. The use of ILs in many branches of science is expanding fast; it is hoped that this review will draw the attention of researchers to the "window of opportunities" that these green solvents open into carbohydrate chemistry.