Ludmila C. Fidale

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.

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.

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.