Lignin supracolloids synthesized from (W/O) microemulsions: use in the interfacial stabilization of Pickering systems and organic carriers for silver metal

Abstract

Taking advantage of the aromatic and cross-linking tendency of lignin macromolecules extracted from plants, we present a novel method for their assembly into supracolloidal structures. Specifically, spherical particles with controllable size (∼90 nm to 1 μm) were obtained from water-in-oil (W/O) microemulsions formulated with a mixture of nonionic surfactants and a colloidal dispersion of a low molecular weight alkali lignin. After spontaneous emulsification, the internal lignin-rich phase was cross-linked to produce the solid particles that could be easily separated by removal of the organic, continuous phase. The efficiency of the fractionated lignin particles to stabilize hexadecane-in-water Pickering emulsions was demonstrated and their properties were compared against those obtained by using traditional inorganic particles. The effect of the particle size of lignin on the emulsion structure is discussed. As a proof of concept we further introduce the use of related emulsions to enable in situ reduction of silver and loading of silver nanoparticles in lignin carriers.

Pickering emulsions: Preparation processes, key parameters governing their properties and potential for pharmaceutical applications

“…For Pickering emulsion stabilization, lignins were used as nanoparticles [213][214][215][216] (see Table 3).…”

“…Lignin nanoparticles can be prepared by numerous preparation methods such as precipitation, emulsification-polymerization [214] and aerosol flow [213]. Lignin can also be modified chemically by, for example, alkylation, acetylation, esterification or polymer grafting.…”

Lignin from Micro- to Nanosize: Production Methods

“…KL particles were synthesized in water-in-oil microemulsions by Nypelö et al [70]. The purified KL was dissolved in a 1 M aqueous NaOH solution.…”

“…Crosslinking and polymerization methods for the production of lignin particles often include toxic and hazardous reaction agents like epichlorohydrin [21,70,71], hydrogen peroxide [20,87] and toluene diisocyanate [35]. However, these production methods show particular advantages for the encapsulation of active substances due to the simple process of crosslinking in mini and macroemulsions.…”

“…in drug delivery or in pickering stabilized emulsions. The size of droplets and therefore, the final size of the capsule in microemulsions can be controlled by adapting the formulation and concentration of surfactants [70,86]. …”