Novel cellulose derivatives. Part VI. Preparation and thermal analysis of two novel cellulose esters with fluorine-containing substituents

Two novel cellulose esters were prepared with fluorine (F)-containing substituents using homogeneous phase reaction chemistry in DMAc/LiCl. The partially substituted derivatives and their corresponding perpropionates proved to be thermoplastic polymers. The 2,2-difluoroethoxy and 2,2,3,3,4,4,5,5-octafluoropentoxy substituents were easily identified by ¹H- and ¹⁹F-NMR spectroscopy without disclosing their precise location on the anhydroglucose unit. Thermal analysis revealed modest or no crystallinity; glass transition temperatures between 53 and 113°C; and improved thermal stability as compared to their F-free counterparts.     

Structure and properties of regenerated cellulose fibers from different technology processes

The crystalline and microstructure of the regenerated cellulose fibers prepared from different solvents and technology processes were investigated by synchrotron wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS). WAXD results indicated that the crystal orientation, crystallinity of Lyocell and IL-cell fibers were higher than those of Viscose and Newdal fibers. The size of micro-voids located in the cross-section of regenerated cellulose fibers was analyzed based on the results of SAXS. And the technology process had little effect on the radius of the micro-voids. The micro-voids in Viscose and Newdal fibers have longer length (L) and greater misorientation (B_Φ) than that in Lyocell and IL-cell fibers. This reveals that the average void volumes of Viscose and Newdal fibers were larger. Furthermore, the regenerated cellulose fibers from dry-jet-wet-spinning process exhibited completely a higher E-modulus, tenacity than the fibers spun by wet-spinning method did.     

Oxidation of 2-keto-4-thiomethylbutyric acid (KTBA) by iron-binding compounds produced by the wood-decaying fungus Gloeophyllum trabeum

Abstract The ability of iron-binding compounds isolated from the brown-rot fungus Gloeophyllum trabeum to carry out one-electron oxidation reactions was established using a model substrate, 2- keto -4-thiomethylbutyric acid (KTBA). The oxidation reaction was monitored by measuring the amount of ethylene produced from the substrate by gas chromatography. The extent of the reaction was found to be influenced by the concentration of the chelators, and by iron and manganese.     

Characterization of films made with chayote tuber and potato starches blending with cellulose nanoparticles

The aim of this study was to characterize chayotextle starch films reinforced with cellulose (C) and cellulose nanoparticle (CN) (at concentrations of 0.3%, 0.5%, 0.8% and 1.2%), using thermal, mechanical, physicochemical, permeability, and water solubility tests. C was acid-treated to obtain CN. The films were prepared by casting; potato starch and C were used as the control. The solubility of the starch films decreased with the addition of C and CN compared with its respective film without C and CN. No statistical difference (α = 0.05) was found in the films added with different concentrations of C and CN. In general, the mechanical properties were improved with the addition of C and CN, and higher values of tensile strength and elastic modulus were determined in the films reinforced with CN. The melting temperature and enthalpy increased with the addition of C and CN, and the values of both thermal parameters were higher in the films with CN than with C; the enthalpy value of the film decreased when the concentration of C or CN increased in the composite. Low concentration of C and CN is better distributed in the matrix film. The addition of C and CN in the starch films improved some mechanical, barrier, and functional properties.     

Heat insulation performance,mechanics and hydrophobic modification of cellulose–SiO2 composite aerogels

Cellulose–SiO₂ composite hydrogel was prepared by combining the NaOH/thiourea/H₂O solvent system and the immersion method with controlling the hydrolysis–fasculation rate of tetraethyl orthosilicate (TEOS). The hydrophobic composite aerogels were obtained through the freeze-drying technology and the cold plasma modification technology. Composite SiO₂ could obviously reduce the thermal conductivity of cellulose aerogel. The thermal conductivity could be as low as 0.026 W/(mK). The thermal insulation mechanism of the aerogel material was discussed. Composite SiO₂ reduced hydrophilicity of cellulose aerogel, but environmental humidity had a significant influence on heat insulation performance. After hydrophobic modification using CCl₄ as plasma was conducted, the surface of composite aerogel was changed from hydrophilic to hydrophobic and water contact angle was as high as 132°. The modified composite aerogel still kept good heat insulation performance. This work provided a foundation for the possibility of applying cellulose–SiO₂ composite aerogel in the insulating material field.     

Effects of chemical inhomogeneity of corn stalk on solvolysis liquefaction

Structural characterization of corn stalk (CS) factions including whole stalk, ear husk, leaf blade, stem bark and stem pith was conducted. Different fractions were liquefied by solvolysis liquefaction method. Acid number, hydroxyl number and insoluble residues ratios (IRR) of liquefied products from CS factions were monitored. Results showed chemical compositions of CS fractions had remarkable difference. Cellulose, hemicellulose and lignin accounted for 36.9-41.43%, 21.77-37.3% and 3.38-7.52% of the raw material, respectively. Acid numbers increased with increasing time from 30 to 90 min, whereas hydroxyl numbers decreased gradually, IRR decreased and then increased. However, properties of liquefied products differed remarkably. Higher acid number, higher hydroxyl number, and lower IRR were detected from ear husk liquefied products. This is coincident with the higher content of hemicelluloses in ear husk. This work proved that whole utilization process is unsatisfactory in solvolysis liquefaction and different fractions of CS should be given themselves optimum applications.     

The mechanism of formation of Cellulose-like microfibrils in a cell-free system from Acetobacter xylinum

The mechanism of formation of cellulose-like microfibrils by a non-soluble, particulate enzyme and uridine diphosphoglucose (UDPG) in a cell-free system from Acetobacter xylinum was studied by transmission electron microscopy and X-ray diffraction. The suspension of particles to which the enzyme is adsorbed is composed of whole, dense ovoids, 50–250 nm long when wet, of fragments of the ovoids, and amorphous substance. There is a typical unit membrane around each ovoid but initially there is no trace of fibrillar material in the suspension. When the suspension of particles is incubated with UDPG, linear wisps of fibrils are produced which associate rapidly to form longer and wider threads, especially in 0.01 M NaCl. There is no visible attachment of the wisps to the particles. After 20 min incubation, threads with the typical morphology of cellulose microfibrils are formed that later tend to become entangled in clumps. The microfibrils are insoluble in hot, aqueous, alkaline solutions and resistant to the action of trypsin, but may be degraded by glusulase. After treatment with 1 M NaOH at 100° C or with cold 18% NaOH they show an X-ray diffraction pattern which resembles that of Cellulose II from mercerized, authentic bacterial cellulose. Incorporation of radioactive glucose into the insoluble residue is enhanced by drying of the cellulose microfibrils before alkaline digestion and especially by the addition of a gross excess of carrier cellulose after incubation. In this system there is no evidence for participation of linear, axial, synthesizing sites on the cell wall of the bacterium or for ordered, organized granules in the assembly of the microfibrils. That is, cellulose-like microfibrils may be formed in a cell-free system without the action of any of the previously suggested cell organelles. In addition, these observations are consistent with a previously described notion of a transient, hydrated, nascent, bacterial cellulose microfibril. The possibility that cellulose microfibrils of green plants may be formed in the same way is considered.N.R.C.C. 18314     

Cellulose and pectin localization in roots of mycorrhizalAllium porrum: labelling continuity between host cell wall and interfacial material

Two different types of contacts (or interfaces) exist between the plant host and the fungus during the vesicular-arbuscular mycorrhizal symbiosis, depending on whether the fungus is intercellular or intracellular. In the first case, the walls of the partners are in contact, while in the second case the fungal wall is separated from the host cytoplasm by the invaginated host plasmamembrane and by an interfacial material. In order to verify the origin of the interfacial material, affinity techniques which allow identification in situ of cell-wall components, were used. Cellobiohydrolase (CBH I) that binds to cellulose and a monoclonal antibody (JIM 5) that reacts with pectic components were tested on roots ofAllium porrum L. (leek) colonized byGlomus versiforme (Karst.) Berch. Both probes gave a labelling specific for the host cell wall, but each probe labelled over specific and distinct areas. The CBH I-colloidal gold complex heavily labelled the thick epidermal cell walls, whereas JIM 5 only labelled this area weakly. Labelling of the hypodermis was mostly on intercellular material after treatment with JIM 5 and only on the wall when CBH I was used. Suberin bands found on the radial walls were never labelled. Cortical cells were mostly labelled on the middle lamella with JIM 5 and on the wall with CBH I. Gold granules from the two probes were found in interfacial material both near the point where the fungus enters the cell and around the thin hyphae penetrating deep into the cell. The ultrastructural observations demonstrate that cellulose and pectic components have different but complementary distributions in the walls of root cells involved in the mycorrhizal symbiosis. These components show a similar distribution in the interfacial material laid down around the vesicular-arbuscular mycorrhizal fungus indicating that the interfacial material is of host origin.