CELLULOSE SYNTHASE INTERACTING 1 is required for wood mechanics and leaf morphology in aspen.

Cellulose microfibrils synthesized by CELLULOSE SYNTHASE COMPLEXES (CSCs) are the main load-bearing polymers in wood. CELLULOSE SYNTHASE INTERACTING1 (CSI1) connects CSCs with cortical microtubules, which align with cellulose microfibrils. Mechanical properties of wood are dependent on cellulose microfibril alignment and structure in the cell walls, but the molecular mechanism(s) defining these features is unknown. Herein, we investigated the role of CSI1 in hybrid aspen (Populus tremula × Populus tremuloides) by characterizing transgenic lines with significantly reduced CSI1 transcript abundance. Reduction in leaves (50-80%) caused leaf twisting and misshaped pavement cells, while reduction (70-90%) in developing xylem led to impaired mechanical wood properties evident as a decrease in the elastic modulus and rupture. X-ray diffraction measurements indicate that microfibril angle was not impacted by the altered CSI1 abundance in developing wood fibres. Instead, the augmented wood phenotype of the transgenic trees was associated with a reduced cellulose degree of polymerization. These findings establish a function for CSI1 in wood mechanics and in defining leaf cell shape. Furthermore, the results imply that the microfibril angle in wood is defined by CSI1 independent mechanism(s).

Colloidal stability of aqueous nanofibrillated cellulose dispersions.

Cellulose nanofibrils constitute an attractive raw material for carbon-neutral, biodegradable, nanostructured materials. Aqueous suspensions of these nanofibrils are stabilized by electrostatic repulsion arising from deprotonated carboxyl groups at the fibril surface. In the present work, a new model is developed for predicting colloidal stability by considering deprotonation and electrostatic screening. This model predicts the fibril-fibril interaction potential at a given pH in a given ionic strength environment. Experiments support the model predictions that aggregation is induced by decreasing the pH, thus reducing the surface charge, or by increasing the salt concentration. It is shown that the primary mechanism for aggregation upon the addition of salt is the surface charge reduction through specific interactions of counterions with the deprotonated carboxyl groups, and the screening effect of the salt is of secondary importance.

Potentiometric titrations of five synthetic tetraacids as models for indigenous C80 tetraacids.

The acid/base properties, critical micelle concentrations (cmcs), and pH-dependent solubility of five synthetic tetraacids have been studied at several ionic strengths (20-600 mM NaCl) and in the pH range of 1.5-11 using high precision potentiometric titrations, tensiometer measurements, and UV spectroscopy, respectively. The molecular weight of the tetraacids ranged between 478 and 983 g/mol. The potentiometric titration data was evaluated in terms of thermodynamic equilibrium models, developed in the light of relevant solubility data, Langmuir monolayer compressions and cmc of the different tetraacids. The results indicate that for two of the tetraacids, called BP5 and BP7, two chemical forms fully dominate the speciation of the monomers; the insoluble fully protonated form, and the soluble fully deprotonated form. The partly protonated species, only play a very minor role in the speciation of these tetraacids. For the other tetraacids the results are more complicated; for the smallest tetraacid, called BP1, all species seem to play important roles, and for the most hydrophobic, BP10, the formation of micelles and aggregates severely complicates the evaluation of the speciation. For the tetraacid BP3 one of the partly deprotonated forms seems to be important, thus confirming the structure to properties relationship. In spite of the complicated micelle formation chemistry, and although not actually measured, the acid/base properties for the monomers of BP10 were interpreted by means of surface charge densities of the micellar aggregates. The modeling indicates an increase of the aggregation number of the micelle upon acidification, a result of formation of mixed micelles incorporating the fully protonated and deprotonated species. An intrinsic pK(a) of 5.4 for BP5 was used to model the monomer pK(a) of BP10, and corresponded well with a monolayer acidity constant pK(s)(a) of 5.5 obtained from surface collapse pressures of Langmuir monolayers as a function of pH.

New quaternized cellulose based on hydroxyethyl cellulose (HEC) grafted EDTA: Synthesis, characterization and application for Pb (II) and Cu (II) removal.

In this paper, new quaternized cellulose derivative based on Ethylenediaminetetraacetic acid (EDTA) and hydroxyethyl cellulose (HEC) is successfully prepared in homogeneous medium. The resulted product is characterized using spectroscopy techniques (FTIR, 1H NMR and 13C NMR). At the supramolecular level, the x-ray patterns show that a high hydrogen bond density occurs by grafting EDTA on the HEC fibers. The new adsorbent (HEC-EDTA) shows a high adsorption capacity of heavy metals (Pb (II) and Cu (II)) from aqueous metals solutions. The adsorption of the both metal ions follows the pseudo-second-order kinetic model, while the adsorption isotherms are well described by the Langmuir model. The qm values are determined for Pb (II) and Cu (II), respectively. For each metal, the equilibrium adsorption time is found to be 30min. Moreover, the HEC-EDTA adsorption capacity is strongly dependent on the pH value; and the adsorption is favorable for pH values ​​between 4 and 6. Moreover, the results show a high affinity toward Cu (II) than Pb (II).

Alkalization of dissolving cellulose pulp with highly concentrated caustic at low NaOH stoichiometric excess.

We present a quantitative study, using Raman spectroscopy combined with multivariate data analysis, to determine the degree of activation of softwood sulphite dissolving cellulose pulp by aqueous sodium hydroxide. We have chosen industrially relevant conditions, including low stoichiometric ratio of NaOH/Anhydroglucose Unit (AGU)<2 and highly concentrated caustic (≥45% w/w [NaOH]). A design of experiments is used to investigate the effects of simultaneous variation of a set of key parameters on the degree of activation (i.e. transformation to alkali cellulose, denoted as DoA): (a) the NaOH/AGU stoichiometric ratio, denoted (r); (b) the concentration of NaOH, denoted [NaOH]; (c) temperature, denoted (T); and (d) reaction time, denoted (t). Solid-state 13C CP/MAS NMR spectroscopy was applied to investigate the reproducibility of the experiments and to select the range for (t). According to the model, (r) is found to have a statistically significant effect on DoA (increasing from DoA=6-30% at the lowest (r)=0.8, to DoA=48-87% at the highest (r)=1.8), together with [NaOH]. The influence of [NaOH] depends strongly on (r). The other studied variables are found to be insignificant in the model and has a complicated influence on the activation. In particular, (T) is found to be unimportant in the studied range (30-60°C), but increasing (t) from 5 to 25min shows a positive influence on DoA, depending on both (r) and [NaOH]. A mercerisation mechanism that is controlled by diffusion is proposed to explain these phenomena.

Ionic liquid mediated technology for synthesis of cellulose acetates using different co-solvents.

In this work, cellulose acetate was synthesized under homogeneous conditions. Cellulose was first dispersed in acetone, acetonitrile, 1,5-diazabicyclo(4.3.0)non-5-ene (DBN) or dimethyl sulphoxide (DMSO) and the resulting suspension was dissolved in an ionic liquid, 1,5-diazabicyclo(4.3.0)non-5-enium acetate [HDBN][OAc] at 70°C for 0.5h. It was possible to dissolve more than 12wt% cellulose with a degree of polymerization in the range of 1000-1100. The dissolved cellulose was derivatized with acetic anhydride (Ac2O) to yield acetylated cellulose. As expected, the use of the co-solvents improved the acetylation process significantly. In fact, cellulose acetates with different properties could be obtained in half an hour, thus facilitating rapid processing. When DBN was used as the dispersing agent (the precursor of the ionic liquid), the problems associated with recycling of the ionic liquid were significantly reduced. In fact, additional [HDBN][OAc] was obtained from the interaction of the DBN and the by-product, acetic acid (from Ac2O). However, the cellulose acetate obtained in this manner had the lowest DS. Consequently, the native cellulose and acetylated celluloses were characterized by means of (1)H- and (13)C-NMR, FT-IR, GPC/SEC and by titration. The cellulose acetates produced were soluble in organic solvents such as acetone, chloroform, dichloromethane and DMSO which is essential for their further processing. It was demonstrated that the ionic liquid can be recovered from the system by distillation and re-used in consecutive acetylation batches.

A morpholinium ionic liquid for cellulose dissolution.

A series of substituted morpholinium ionic salts and allyl ammonium acetates were prepared. Amongst those, N-allyl-N-methylmorpholinium acetate ([AMMorp][OAc]) was found to dissolve cellulose readily without any pre-processing of native cellulose. At 120°C, [AMMorp][OAc] could dissolve 30 wt%, 28 wt% and 25 wt% of cellulose with degree of polymerization (DPn) - 789, 1644 and 2082 respectively, in 20 min. Importantly, SEC analysis indicated that no discernible changes occurred in terms of the degree of polymerization of the different celluloses after regeneration. Furthermore, when comparing the cellulose dissolution capability of these newly synthesized ionic liquids, it is evident that the combination of all three constituents - the morpholinium cation, the existence of an allyl group and choosing the acetate anion are essential for efficient cellulose dissolution. The structure and morphology of the regenerated cellulosic materials were characterized by SEM, XRD, TGA, CP/MAS (13)C NMR and FTIR, respectively.

Multilayers of cellulose derivatives and chitosan on nanofibrillated cellulose.

The aim of this work was to study the effect of solution conditions and polysaccharide structure on their Layer-by-Layer (LbL) deposition on nanofibrillated cellulose (NFC). Multilayer build-up of cellulose derivatives and chitosan on NFC model surfaces was studied using Quartz Crystal Microbalance with Dissipation (QCM-D) and Colloidal Probe Microscopy (CPM). The type of cationic polysaccharide was found to significantly affect the multilayer build-up and surface interactions. Cationic cellulose derivative quaternized hydroxyethyl cellulose ethoxylate (HECE) formed highly water-swollen layers with carboxymethyl cellulose (CMC), and the build-up was markedly influenced by both the ionic strength and pH. The ionic strength did not significantly influence the multilayer build-up of chitosan-CMC system, and adsorbed chitosan layers decreased the viscoelasticity of the system. Based on the results, it was also confirmed that electrostatic interaction is not the only driving force in case of the build-up of polysaccharide multilayers on nanofibrillated cellulose.

Interactions between GaO4Al12(OH)24(H2O)12(7+) and cellulosic materials.

The adsorption qualities of GaO(4)Al(12)(OH)(24)(H(2)O)(12)(7+), a polycation with ε-Keggin structure, and its stability in contact with anionic cellulosic materials, was investigated under different concentration and ionic strength conditions. The cellulosic materials employed were two different fully bleached fibre materials, carboxyl methyl cellulose (CMC), and a spin-coated cellulose model surface. As analytical techniques, pH-measurements, potentiometric titrations, ICP-OES, QCM-D, equilibrium calculations and Extended X-ray Absorption Fine Structure (EXAFS) were used. The adsorption is substantial and the addition of GaO(4)Al(12)(OH)(24)(H(2)O)(12)(7+) to a fibre suspension results in a rapid decrease in pH, followed by a small and slow increase in pH. This behaviour can be explained as due to a rapid and strong (log ß>2) equilibrium adsorption of intact GaO(4)Al(12)(OH)(24)(H(2)O)(12)(7+) ions, followed by a slow, and minor, 3-8%, decomposition into different monomers. Alternative layer by layer adsorption of this ion, and CMC, on a spin-coated cellulose model surface constitutes further evidence for the strong interactions between the anionic cellulose materials and GaO(4)Al(12)(OH)(24)(H(2)O)(12)(7+). It is shown that the adsorption observed could not be described as due to an unspecific Donnan adsorption behaviour, neither of GaO(4)Al(12)(OH)(24)(H(2)O)(12)(7+) nor Ga and Al monomers, and specific surface complex formation is therefore discussed and applied. The (≡COO)(7)GaO(4)Al(12)(OH)(24)(H(2)O)(12) species found to explain the pH- and metal adsorption data should be considered strictly as a stoichiometric entity.

Use of nanoparticular and soluble anionic celluloses in coagulation-flocculation treatment of kaolin suspension.

In this work, the effectiveness of a novel, combined coagulation-flocculation treatment based on alum and soluble or nanoparticular anionic derivatives of dialdehyde cellulose, ADAC, was evaluated by studying the removal of colloidal material in a model suspension containing kaolin. Four different ADACs with varying degrees of substitution, size and water solubility were synthesized by periodate oxidation and sulfonation of cellulose. The effects of ADAC dosage, solution pH and temperature on flocculation were studied by measuring residual turbidity of the settled suspension. Moreover, the charge densities, sizes, ζ-potentials and stability of the ADACs in aqueous solutions were studied. The combined treatment was effective in the removal of colloidal particles, as demonstrated by reduced residual turbidity with remarkably lower total chemical consumption compared with coagulation with alum alone. Of the ADACs, samples with lower solubility that contained cellulose nanoparticles performed better than the fully water-soluble sample. Due to the restricted pH tolerance of alum, the combined treatment was effective only at acidic conditions (pH < 5), although the ADACs were found to be stable in a much broader pH range (pH of 3 to about 9). ADACs also retained strong activity at higher temperatures (30-60 °C) and after several days of storage in aqueous solution.

Flocculation performance of a cationic biopolymer derived from a cellulosic source in mild aqueous solution.

The flocculation behavior of cationic, quaternary ammonium groups containing cellulosic biopolymers, CDACs, synthesized by cationizing dialdehyde cellulose in mild aqueous solution was studied in a kaolin suspension. In particular, the role of CDAC dosage and solution pH, NaCl concentration, and temperature were clarified. In addition, the initial apparent charge densities (CDs), particle sizes, ζ-potential, and stability of CDs were determined. CDACs possessed a high flocculation activity in neutral and acidic solutions, but a significant decrease was observed in alkaline solutions (pH >9). This was also seen as a decline in the apparent CD and particle size of the CDACs in alkaline conditions. The measurements also indicated that the apparent CD decreased to a constant level of 3 mmol/g in aqueous solutions. However, no notable decrease in flocculation performance was obtained after several days of storage. Moreover, the variation of NaCl concentration and temperature did not affect the flocculation activity.

A multitechnique study of the interactions between H+, Na+, Ca2+ and Cu2+, and two types of softwood Kraft fibre materials.

Aiming for a better understanding of the interactions between water suspended cellulose fibres and metal ions, this study was focused on characterising the interactions between Ca2+, Cu2+ and two different fibre materials--a fully bleached softwood Kraft pulp, and a chemically modified fully bleached softwood Kraft fibre material. The study was conducted as a function of pH (2-7), and both in the absence and presence of an excess of Na+ ions, 0-100 mM Na(Cl). For both fibre materials, adsorption data collected in the absence of Na+ were fully explained by the unspecific Donnan ion-exchange model. However, in an excess of Na(Cl), data clearly indicated that higher amounts of divalent metal ions adsorbed, than predicted by the Donnan model. Therefore, to model these data, specific metal ion-fibre surface complexes were assumed to form, in addition to the Donnan ion-exchange. A neutral surface species involving two surface carboxylate groups and one metal ion was, for both metal ions, found to yield a good description of data at all ionic strengths. In the case of Cu2+, the existence of this complex was corroborated by Cu K-edge EXAFS data, suggesting that copper ions interacts directly with carboxyl groups present int the fibres. EXAFS data also indicate that one Cu2+ interacts with two carboxyls.