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This study aims to overcome the challenges of high-value utilization of technical lignins that encounters chemical complexity, heterogeneity and broad molecular mass distribution. Kraft lignin was fractionated through a practical strategy involving sequential dissolution in solvents of different polarities (water, tetrahydrofuran, and water/tetrahydrofuran v/v = 3/7). Lignin self-assembled drawing on the anti-solvent method, generating particles of controllable surface energy. Considering the governing factors in multiphase stabilization, the morphology, wetting characteristics and chemical composition of the kraft lignin particles (KLPs) were examined as a means to achieve controllable Pickering stabilization of oil-in-water (O/W) emulsions. The most anionic and hydrophilic KLPs formed aggregated networks (∼185 nm), which acted as a surfactant-type emulsifier following reversible adsorption at the O/W interfaces. Notably, the particles of the least hydrophilicity (∼146 nm) displayed a characteristic hollow structure. Such particles adsorbed slowly and weakly at the O/W interface, forming a viscoelastic layer around the oil droplets. The smallest lignin particles (∼39 nm) presented an intermediate hydrophilic character. They were uniform in size and formed rigid interfacial layers on the oil droplets. Accordingly, the devised relationship between particle morphogenesis and O/W stabilization capacity enabled the customization of lignin (size and wetting characteristics), allowing broader utilization in multiphase systems. [ABSTRACT FROM AUTHOR]

We introduce Kraft lignin colloids produced by destabilization of a kraft lignin solution by pH shift from 2 to 11. The system includes lignin particles and hydrocolloid aggregates in equilibrium (KLP), which are used to control the emulsifying energy and to stabilize oil-in-water emulsions under high energy at pH 11 and 7, yielding excellent stability (at least three months with no creaming). We investigate emulsify technology (ultrasonication and homogenization), energy input (high energy or low energy), particle desorption, drop size, and rheology on the stability of KLP-based Pickering emulsions according to the system's pH. The ultrasonication leads to fine, stable and homogenous lignin emulsions without observing macroscopic creaming phenomenon, whereas homogenization only limits to alkaline condition. Regarding homogenization process, increasing the energy input helps to reduce the emulsion droplet size and consequently improves emulsion stability. In addition, the emulsion produced at acidic conditions always presented excellent stability, independent of the emulsify parameters. Considering the synergistic effects of emulsification protocol, surface activity, and particle interactions, the results indicate the possibility of extending the applications of kraft lignin as a Pickering stabilizer in neutral and alkaline conditions. It also creates a promising method to control the stability and emulsion microstructure in the industrial KLP based emulsion preparation process. [Display omitted] • Lignin stabilized emulsions were extended from acidic to pH 11. • A synergistic stabilization mechanism at high pH is proposed. • Emulsification process and energy input impact the formation and stability of emulsions. • Emulsions are stable for over three months. • E desorption increases for emulsions stabilized by lignin in the order of pH 11 < 7 < 2. [ABSTRACT FROM AUTHOR]

[Display omitted] The lignin nanoparticles (LNPs) synthesis relies on lignin polymers with heterogeneous molecules and properties, which impose significant limitations on the preparation and property regulation. The multiscale structure of lignin from monomers to oligomers, provides a potential pathway for precise regulation of its physical and chemical properties. The study addresses this challenge by employing coniferyl alcohol and sinapyl alcohol as monomers and separately utilizing the Zulaufverfaren (ZL) and Zutropfverfaren (ZT) methods to synthesize different types of lignin dehydrogenation polymers (DHPs) including guaiacyl (G)-ZL-DHP, G-ZT-DHP, syringyl (S)-ZL-DHP, and S-ZT-DHP. The investigation highlights the chemical bonds as essential components of lignin primary structure. Additionally, the secondary structure is influenced by branched and linear molecular structures. G unit provides some branching points, which are utilized and amplified in the ZL process of DHPs synthesis. The branched DHPs aggregate at the edge and form rod-like LNPs. While linear DHPs aggregate around the center, presenting polygonal LNPs. The study identifies that the branched LNPs, characterized by more surface charges and lower steric hindrance, can form a stable complex with chitin nanofibers. Emulsions with varying oil-to-water ratios were subsequently prepared, opening a new window for the application of LNPs in fields such as food and cosmetics. [ABSTRACT FROM AUTHOR]