Preparation of hemicellulosic derivatives with bifunctional groups in different media

Valorization of industrial xylan-rich hemicelluloses into water-soluble derivatives by in-situ acetylation in EmimAc ionic liquid

In this study, aimed at valorization of industrial xylan-rich hemicelluloses (a by-product of dissolving pulp process), water-soluble hemicelluloses were fabricated with mild acetylation in 1-ethyl-3-methylimidazolium acetate ionic liquid (EmimAc) and dichloroacetyl chloride (Cl₂AcCl) system by a facile and novel method. The structure of the acetylated hemicelluloses was characterized by FT-IR and NMR spectra. The resultant modified products could fully dissolve in water with the degree of substitution (DS) valued between 0.17 and 0.37. Structural characterization indicated that the modified hemicelluloses were chiefly composed of the (1 → 4)-linked β-D-Xylp backbone with hydroxyl or -COCH₃ linked to O-2 and O-3 of the Xylp units. Moreover, the mild acetylation was achieved by one-pot method, in which the hemicelluloses reacted with mixed anhydride produced between EmimAc and Cl₂AcCl rather than Cl₂AcCl. Rheological behavior measurements revealed that acetylated hemicelluloses solutions showed shear-thinning behavior and indicated lower viscosity compared with those of the referenced hemicelluloses. The excellent water-solubility of industrial hemicelluloses would widen its application field and be easier for its conversion into desired chemicals.

Investigation of the Thermo-Mechanical Properties of Blend Films Based on Hemicelluloses and Cellulose

This study presents an effective and convenient approach to prepare blend films with enhanced mechanical and thermodynamic properties by incorporation of carboxymethyl cellulose (CMC) into quaternized hemicelluloses (QH). The structures and properties of films were analyzed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and tensile testing, respectively. From the SEM pictures, tight, homogeneous, and smooth surfaces of films were obtained. In addition, the transparencies of the blend films were increased with the increasing of CMC content. The results of mechanical properties indicated that the blend film prepared from QH and CMC (1 : 2 m/m) had a tensile strength of 65.2 MPa. It suggested that the addition of CMC was contributed to mechanical properties by strong electrostatic interactions and the enhanced hydrogen bondings with QH. These results provide insights into the understanding of the structural relationships of bioblend films in coating and packaging application.

Ionic Liquid-Mediated Homogeneous Esterification of Cinnamic Anhydride to Xylans

A new functional biopolymer was synthesized through an ionic liquid-mediated homogeneous grafting of cinnamic anhydride to xylans. The ionic liquid used was 1-allyl-3-methylimidazolium chloride (AMIMCl) ionic liquid. Xylans with degrees of substitution (DS) between 0.11 and 0.57 were accessible in a completely homogeneous system by changing catalysts (NaOH, KOH and LiOH), time, reaction temperature, and cinnamic anhydride/xylan molar ratio. The chemical structure and the thermal stability of the derivatives were characterized by Fourier transform infrared spectroscopy (FT-IR), ¹³C-NMR spectroscopy, and thermogravimetry. The thermal stability of the derivatives was reduced compared with the original xylan. Possible applications of the cinnamic anhydride-acylated xylan derivatives include wet-end papermaking, organic–inorganic composite films, and hydrogels.

Novel hydrophobic hemicelluloses: synthesis and characteristic

Novel hydrophobic hemicelluloses possessing hydrophobic groups were prepared by the benzylation of wheat straw hemicelluloses with benzyl chloride under the presence of catalyst in an ethanol/water system. In particular, the progress of the benzylation reaction was studied as a function of the volume ratio of ethanol/water from 4:1 to 6:4, the molar ratio of NaOH/anhydroxylose unit in hemicelluloses from 0.6:1 to 1.5:1, the molar ratio of benzyl chloride/anhydroxylose unit in hemicelluloses from 0.5:1 to 2.0:1, reaction temperature 50-80 °C, and reaction time 4-20 h Benzylated hemicelluloses with the low degree of substitution from 0.09 to 0.35 were obtained depending on the experimental conditions. The incorporation of benzyl groups into the backbone of hemicelluloses was confirmed by FT-IR and (13)C NMR spectroscopies. The thermal stability increased after the modification of hemicelluloses due to the introduction of benzyl groups. The introduction of benzyl groups endows hemicelluloses with the hydrophobicity, which could be potentially applied in plastic industries.