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Aiming to improve the poor miscibility between lignin and non-polar materials, alkali lignin (AL) was self-assembled into lignin reverse micelles (LRM) and blended with high-density polyethylene (HDPE) to fabricate composite films. The particle size of AL increased from 3.5 nm to 130 nm after forming LRM, showing a uniform spherical morphology. The water droplet contact angle increased from 54° to 89°. Optimal and rheological analysis revealed that composite films exhibited good transparency, ultraviolet (UV)-blocking performance and low viscoelasticity after adding the nano LRM. Under the optimal dosage of 5 wt% LRM, the composite film can screen 93% UV rays, and the apparent viscosities, complex viscosities, storage and loss modulus of the mixture were the lowest. Atomic force microscopy (AFM) was used to investigate the molecular interactions between lignin and HDPE. The average adhesion force between LRM and HDPE in dry air was 1.07 mN m−1, while that between AL and HDPE was 0.77 mN m−1. AFM experiments fundamentally demonstrated better compatibility between LRM and HDPE, which was beneficial for the improvement of UV-blocking, rheological properties, as well as their processability of LRM/HDPE films. [ABSTRACT FROM AUTHOR]

Owing to its high aromaticity and carbon content, technical lignin as the by-product of chemical pulping and bio-refining industry can be converted into lignin-derived porous carbon (LPC) materials after activation, which is a promising strategy for high-value utilization. In particular, LPC with a higher surface area and graphitization will have a broad prospect as the electrode material for lithium-ion batteries (LIBs). However, the structure of technical lignin varies greatly due to its different industrial processes and botany sources, which remarkably affects the activation process and electrochemical properties of LPC. Herein, we study the effect of oxygen/carbon (O/C) ratio and molecular weight on the structure of LPC by exploring the effect of four kinds of technical lignin on K2CO3 activation. High O/C ratio can promote LPC to maintain a high specific surface area (SSA). High molecular weight and low O/C ratio were beneficial to increase the graphitization degree and keep the porous structure of LPC. The electrochemical performance evaluation showed that high graphitization and stable porous structure were beneficial for lithium-ion storage. Therefore, LPC from enzymatic hydrolysis lignin (EHL) had long cycle performance (490 mAh · g−1 at a current density of 400 mA · g−1) and excellent rate performance compared to lignin from chemical pulping. [ABSTRACT FROM AUTHOR]

Organosolv lignin (OL) extracted from pine wood was self-assembled into uniform nanocolloidal spheres (OLCS) in acetone/water and blended with varnish for better UV-blocking and antioxidant performance. The UV transmittance of the varnish with 1% OL was lower than that of a commercial varnish containing synthetic UVA and UVB blocker. Samples coated with OL-based varnish and UV irradiated for 100 h showed 84 and 69% less color change, respectively, compared to that of pure and commercial varnishes. Due to the higher surface area and better compatibility, the varnish blended with 1% OLCS showed better UV-blocking and photostability than those based on 1% OL additive. The color change of varnish was not perceptible. The lignin-based additives significantly enhanced the hardness and adhesion performance of the varnish and had little influence on the esthetic appearance of the samples. The hardness and modulus of elasticity of varnish increased by 61 and 36%, respectively, in the presence of 1% OLCS. The possible enhancement mechanism was explained by molecular interaction forces. [ABSTRACT FROM AUTHOR]

Phosphorylated kraft lignin (PKL), a novel lignin polymer, has potential application in the preparation and modification of inorganic materials. In this article, the adsorption characteristics of PKL at the solid/liquid interface were investigated under different pH conditions. Quartz crystal microbalance combined with dissipation monitoring (QCM-D), UV spectroscopy, and atomic force microscopy (AFM) were applied for monitoring the adsorption. The adsorbed amount of PKL gradually decreased as a function of pH increment on the gold covered QCM-D crystals, which were pretreated with an adsorbed layer of poly(diallyldimethylammonium chloride) (PDAC). This was also the case for quartz slide substrates pretreated with PKL/PDAC multilayers by the method relying on the layer-by-layer (LBL) electrostatic self-assembly. The hydrophobicity of adsorbed PKL films increased with increasing pH from 3 to 12. In the course of this process, the adsorption morphology changed from a compact rigid state to a less compact soft state. Under acidic conditions, the adsorption is governed mainly by cation-π interaction between PKL and PDAC, and the adsorption configuration is mushroom-like. Under neutral and alkaline conditions, the cation-π interaction is less relevant owing to the longer distances between the anionic groups in PKL and the cation in PDAC. This causes stretching of the molecular chains in PKL, while the adsorption configuration changes to a planar pancake structure so that the electrostatic interaction dominates. The knowledge on adsorption characteristics of PKL at different pH values is helpful to prepare some lignin-based composite materials. [ABSTRACT FROM AUTHOR]

Kraft lignin (KL), a by-product in the pulping and papermaking industry, is an abundant, renewable resource. In this work, nanosphere formation of KL has been investigated via self-assembly induced by adding water to a KL/dioxane solution. The KL nanospheres were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), dynamic light scattering (dynLS) and static light scattering (statLS). It was found that the nanoparticles have uniform nanospherical morphologies, including a small hollow cavity space in the interior. The π-π interactions between the aromatic rings of KL are demonstrated to be an important driving force in the self-assembly process. The KL nanosphere sizes can vary by hundreds of nanometers depending upon the preparation conditions. These newly obtained KL nanospheres have the advantages of biocompatibility, biodegradability, low toxicity, easy preparation, and low cost. Thus KL nanospheres are attractive for applications in life science, medicine, biology, food science, and agriculture. This approach presented here is an economically feasible and facile strategy for the sustainable utilization of kraft lignin. [ABSTRACT FROM AUTHOR]

The correlation between the hydrophilicity of sodium lignosulfonate (NaLS) and its dispersing performance towards pesticide particles has been investigated. NaLS was classified into three fractions by adsorption chromatography on macroporous resins. A positive correlation has been found between the hydrophilicity and the contents of phenolic hydroxyl and sulfonic acid groups. On the other hand, the NaLS fraction with high carboxyl content is not strong hydrophilic. With decreasing the hydrophilicity of NaLS, its amounts on pesticide particles surface increased and the dispersing performance of pesticide particles was improved. Obviously, NaLS and pesticides with similar hydrophilicity match better according to the 'similarity-intermiscibility' theory. Carboxymethylated alkali lignin (CML) is not as hydrophilic as NaLS. The adsorption and dispersing performance of CML for hydrophobic pesticide particles are better than those of NaLS, demonstrating that lignin formulations with lower hydrophilicity are an alternative to obtain excellent pesticide dispersants. [ABSTRACT FROM AUTHOR]

A light-colored hydroxypropyl sulfonated alkali lignin (HSAL) was synthesized based on pine alkali lignin (AL) by grafted-sulfonation and crosslinking reaction processes. The reactions were evaluated by gel-permeation chromatography (GPC), infrared (IR) and proton nuclear magnetic resonance (1H-NMR) spectroscopy. The sulfonic group content and the molecular weight ( M w) of HSAL significantly increased, while the phenolic hydroxyl groups diminished by around 80% compared to AL. The color of HSAL turned to light yellow compared to the dark brown color of AL, that is, it stained less the fiber. The dispersity, heat stability, and dye uptake of dye bath with HSAL was significantly improved compared to sodium lignosulfonate, sulfomethylated AL, and dispersants of the naphthalene series. [ABSTRACT FROM AUTHOR]

The process sulfite pretreatment to overcome recalcitrance of lignocelluloses (SPORL) has been the focus of this study. Pilot-scale (50 kg) pretreatment of wood chips of lodgepole pine ( Pinus contorta Douglas ex Loudon) killed by mountain pine beetle ( Dendroctonus ponderosae Hopkins) were conducted at 165°C with a dilute sulfite solution of pH 2 for bioconversion to ethanol and lignosulfonate (LS). The pretreatment duration was optimized in laboratory bench scale experiments with a certain severity based on a combined hydrolysis factor (CHF). The sodium bisulfite loading was 8% and the liquor to wood ratio 3. The pretreated solids were disk milled together with the spent liquid and the resultant slurry with a 25% solids content was directly (without detoxification) submitted to a simultaneous enzymatic saccharification and fermentation (SSF) with Saccharomyces cerevisiae YRH400 at cellulase loading of 35 ml kg-1 of untreated wood. At solids loading of 20%, the alcohol yield was 288 l t-1 wood (with a final concentration of 52.2 g l-1), which corresponds to a 72.0% theoretical yield based on total glucan, mannan, and xylan. The LS from SPORL was highly sulfonated and its molecular weight was lower than that of a purified commercial softwood LS, and therefore it has a high potential as a directly marketable co-product. [ABSTRACT FROM AUTHOR]

Lignosulfonic acid (LS) has been applied both as dispersant and dopant for chemical polymerization of 3,4-ethylenedioxythiophene (EDOT). EDOT is successfully polymerized in LS aqueous solutions, resulting in a water-dispersive poly(3,4-ethylenedioxythiophene) (PEDOT) conductive nanoparticle (PEDOT:LS). The structure, intermolecular interaction, and performance of the PEDOT:LS were investigated by ultraviolet-visible-Near-infrared spectrophotometry, Fourier transform infrared spectroscopy, thermogravimetric analysis, dynamic light scattering, transmission electron microscopy, X-ray photoelectron spectroscopy, and surface resistivity tester. Results were interpreted in a way that PEDOT:LS is a polyelectrolyte complex, in which the highly hydrophobic PEDOT is in the inner part of the particle and the LS-rich layer with high hydrophilicity is on its surface. During oxidizing reaction of EDOT to PEDOT in LS, the water-insoluble PEDOT product is adsorbed on the surface of water-soluble LS by electrostatic attraction and forms PEDOT:LS polyelectrolyte complexes. In this process, excess LS is needed to be adsorbed on the surface of PEDOT:LS complexes. The process is driven by π-π interaction to increase the water solubility and contributes to a continuous polymerization. The PEDOT:LS as coating has a good conductivity, transparency, humidity resistance, water resistance, and thermal stability and can be used as high-performance antistatic agents. [ABSTRACT FROM AUTHOR]

The solution behavior and molecular conformation of sodium lignosulfonates (NaLS) in saline solution has been studied by means of static and dynamic light scattering (LSstat and LSdyn). Results show that the salt content must be larger to eliminate the slow mode in LSdyn analysis of NaLS than that of the theory, and this discrepancy can only be explained by a modified microgel model. The higher salt amount is needed for the formation of a strong ionic gradient field between surface and the inner part of NaLS, which forces counter ions to penetrate into the inner part of NaLS to screen the small amount of charges. The NaLS single molecular shape can be described by an oblate spheroid based on the absolute molecular weight Mw and diffusion coefficients D. The best fitting result is semiaxis a=1.6 nm and axial ratio r=3.5, D=5.73×10-7 cm2 s-1, and the corresponding Mw=1.7×105 g mol-1. [ABSTRACT FROM AUTHOR]

Concentrated sodium lignosulfonate (NaLS) solutions have wide industrial applications. Therefore, the viscoelastic properties of NaLS in concentrations of 55%-63% have been investigated between 5°C and 55°C by means of a dynamic rheological technique, namely, the oscillatory rheological experiments were conducted in a rheometer in the small amplitude oscillatory mode. All solutions showed 'shear-thinning' behavior over frequency. The complex viscosity ( η*) increased and the loss tangent (tanδ) decreased with increasing concentrations. Both the storage modulus ( G′) and the loss modulus ( G″) increased with increasing frequencies and concentrations. The change in viscoelastic behavior was probably caused by stronger aggregation effects. However, the effects of temperature on the viscoelastic properties are more complex. For 60% NaLS, G′, G″, and η* decreased, but tanδ increased with increasing temperatures. When the temperature exceeded 20°C, G′, G″, and η* increased, but tanδ decreased, and the relaxation times were increased as a function of temperature. The change in viscoelasticity as a function of temperature may also be related to intermolecular aggregation and the swelling of aggregates. The conductivity experiments indicated that the formation of a greater strength of network structures at higher levels of concentrations between 55% and 63% and temperatures between 20°C and 55°C was probably responsible for elasticity enhancement. [ABSTRACT FROM AUTHOR]

Carboxymethylated lignin (CML) is well suited as a dispersant or natural adsorbent applied in ceramics, gypsum paste, graphite suspension, and water treatment. In this paper, the effects of COOH content in CML on its behavior in water and the dispersion stability of aqueous graphite suspension has been investigated by means of viscosimetry, surface tension measurement, fluorescence spectrometry, dynamic light scattering (DLS), Turbiscan Lab Expert (TLE) stability analysis, and ζ potential measurement. Viscosimetry clearly revealed the polyelectrolyte effect in diluted aqueous solution of CML. With a higher COOH content of CML, the surface tension of water is reduced. Moreover, the aggregation behavior of CML was strengthened with increasing COOH content, leading to a more compact molecular structure of the aggregates. Based on the results, an aggregation model was proposed to illustrate the variations in the solution behavior of CML with different COOH contents at various concentrations. The dispersion stability of aqueous graphite suspension was improved by adding CML with high COOH content. [ABSTRACT FROM AUTHOR]

Sodium lignosulfonate (NaLS) was dissolved in saline solutions, and the dissolving process was examined by a combination of static and dynamic light scattering. When NaLS was dissolved in 1.2 mol l-1 NaCl solution for 24 h and filtered through a 0.45 μm syringe filter, only a fast relaxation mode was observed, which was attributed to the co-diffusion of NaLS molecular ions and counterions. When the concentration of NaCl was below 1.2 mol l-1 or the dissolving time was <24 h, an additional slow relaxation mode (SRM) appeared due to hindered motions of electrostatically interacting chains. Without filtering or filtering followed by rising temperature to 38°C, SRM appeared due to aggregation, which occurred at a position similar to that caused by electrostatic interaction. For poly(sodium styrenesulfonate) (NaPSS) and modified bamboo lignin derivate with open polyelectrolyte structures, 0.1 mol l-1 NaCl was enough to inhibit the electrostatic interaction. For NaLS with a closed polyelectrolyte structure, the SRM could not be removed until the concentration of NaCl reached 1.2 mol l-1. Above observations give insights for the first time into the relationship between the SRM caused by electrostatically interacting chains and the diffusion mode due to NaLS aggregation, and the influence of the closed polyelectrolyte structure on the SRM. [ABSTRACT FROM AUTHOR]

Single molecules of sodium lignosulfonate (NaLS) were prepared and their aggregation behavior was studied as a function of temperature. The molecular dispersity of the NaLS solutions were confirmed by dynamic light scattering (DLS), and the aggregation behavior was studied by DLS and static light scattering (SLS), fluorescence spectrometry (FS), and atomic force microscopy (AFM). It was demonstrated that NaLS molecules started to aggregate above a critical temperature and the aggregation behavior was related to their spherical microgel conformation and hydrophobic interaction. During the DLS measurement, when NaLS was dissolved in 1.2 mol·l-1 NaCl aqueous solution and then filtered with 0.45 μm syringe filter, the slow-mode diffusion (smD) corresponded to the polyelectrolyte effect and the original aggregates disappeared and the fast-mode diffusion (fmD) corresponded to the monomolecular NaLS (not yet aggregated) in the solution. When the temperature of the NaLS solution was raised to 38°C, the disappeared smD in DLS analysis appeared again, indicating that NaLS molecules started to form new aggregates. Due to the aggregation at 38°C, molecular weight ( Mw) obtained from the SLS had a sharp increase, intensity ratio (I1/I3) of pyrene in FS suddenly decreased, and the adsorption of NaLS on a solid substrate and the corresponding roughness of the surface increased significantly. [ABSTRACT FROM AUTHOR]

The adsorption behavior and dispersion efficiency of sodium lignosulfonate (NaLS) on Al2O3 particles at different pH values were investigated by UV-Vis spectroscopy, zeta potential measurement, X-ray photoelectron spectroscopy, and viscosity measurements. The effects of the additives urea, Na2SO4, and NaCl were tested. At low pH values, NaLS adsorbed on the Al2O3 particles in the form of aggregates and at high pH values as separated single molecules. At pH 3-11, the adsorption was not affected through addition of urea, ruling out hydrogen bond as a controlling factor. By adding Na2SO4 and NaCl, the main driving force was the synergistic effect of the electrostatic interaction and the metal cation-π interaction at pHIEP (IEP, isoelectric point), whereas the metal cation-π interaction was dominant at pH>pHIEP. The dispersing mechanism was mainly attributed to the steric hindrance (at pHIEP) and the electrostatic repulsive force (at pH>pHIEP) owing to the differences in the aggregation state of the adsorbed molecules. [ABSTRACT FROM AUTHOR]

Carboxymethylated lignin (CML) as a water-soluble lignin derivative is a multipurpose adsorbent and dispersant. In this article, the aggregation and adsorption behaviors of CML have been investigated in aqueous solution using fluorescence spectroscopy, dynamic light scattering, and a quartz crystal microbalance combined with dissipation monitoring techniques. It was found that CML forms aggregates when its concentration exceeds the critical aggregation concentration (CAC). The CAC of CML1 with a carboxylic (COOH) group content of 2.8 mmol g-1 was 0.022 g l-1, and that of CML2 with a COOH group content of 2.0 mmol g-1 was 0.026 g l-1. The adsorption behavior of CML on the gold surface was strongly dependent on the pH and ionic strength of the solution. At low pH and ionic strength, more CMLs were adsorbed at the gold/water interface, and the layers were rigid. The results could be used not only from the theoretical but also from the application point of view. [ABSTRACT FROM AUTHOR]

The problems related to the determination of the absolute molecular weight ( Mw) of sodium lignosulfonate (NaLS) are the focus of the present work. Four narrow-dispersed NaLS fractions were collected by filtration, ultrafiltration, and gel permeation chromatography (GPC), and their Mw measured by laser light scattering (LLS Mw) was compared with that obtained by GPC (GPC Mw). The LLS Mw values were much larger than GPC Mw, and this Mw difference increased with increasing Mw of NaLS. This finding confirms the known polyelectrolyte and aggregation effects of NaLS. The deviation is also partly due to the conformation differences between the GPC standard (sodium polystyrene sulfonate) and the NaLS molecules. The effects of polyelectrolytes and NaLS aggregates could be inhibited by adding enough NaCl salt in the NaLS solution and filtering the NaLS/NaCl solution through a syringe filter. As a result, the slow mode in dynamic LLS measurement disappeared. By this approach, the absolute LLS Mw values were only slightly larger than that determined by GPC due to the conformation differences between the GPC standard and the NaLS molecules. [ABSTRACT FROM AUTHOR]

The ability of commercial laccase for improvement of the physicochemical properties of sodium lignosulfonate (NaLS) without any mediator has been investigated. Surface tension, adsorption characteristics, rheological behaviors and fluidity of cement pastes were in focus. Gel permeation chromatography (GPC) shows an initial decrease and then an extensive increase of molecular weight (MW) of NaLS after incubation with laccase. Parallel to MW decrement, the content of phenolic groups is increasing, while an MW increment has the opposite effect. The UV-Vis spectra and the zeta potential of NaLS do not indicate further modification of the substitution pattern on the aromatic ring. The surface tension of NaLS and the adsorbed amount of NaLS on MgO particles is elevated after laccase treatment. The electrostatic attraction between MgO particles and NaLS is the main driving force during this adsorption process. The dispersion efficiency of laccase modified NaLS on the MgO slurry and cement paste is improved. [ABSTRACT FROM AUTHOR]

Soda lignin was converted into sulfonated lignin by oxidation, hydroxymethylation, and sulfonation assisted by microwave irradiation. Oxidation and hydroxymethylation under these circumstances led to lignins with much higher reactivity toward subsequent sulfonation, and the sulfonation degree could be elevated up to 2.75 mmol g-1. A suitable microwave irradiation time is beneficial to obtain oxidized lignin with small molecular size, but the irradiation time must be selected adequately. Under optimal conditions, the sulfonated lignin exhibits a good dispersive effect to TiO2 suspension. Compared to conventional water bath heating, microwave irradiation not only increases the sulfonation degree of lignin, but also sharply shortens the reaction time. [ABSTRACT FROM AUTHOR]