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Lignin-based azo polymer (AL-azo-H) was prepared from alkali lignin (AL) and then used to prepare uniform colloids via self-assembly. Due to the unique UV-blocking performance, AL-azo-H colloids were applied to encapsulate photosensitive pesticide avermectin (AVM). The self-assembled structure of AL-azo-H colloids and their controlled release and anti-photolysis performances for AVM were investigated by dynamic light scattering (DLS), static light scattering (SLS), transmission electron microscopy (TEM) and high performance liquid chromatography (HPLC). Results show that AL-azo-H colloids are hollow spheres. Hollow AL-azo-H colloidal spheres have remarkable AVM encapsulation efficiency as high as 61.49% (w/w). The cumulative release amount of AVM encapsulated by AL-azo-H (AL-azo-H@AVM) after 120 h was 84% and the release was still going on. The decomposition rate of AL-azo-H@AVM was less than 41% even after 72 h of UV irradiation. Hollow AL-azo-H colloidal spheres showed excellent UV-blocking and controlled release performance for AVM. [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 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]

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 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]