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Pickering/Non‐Pickering Emulsions of Nanostructured Sulfonated Lignin Derivatives
Author(s) -
Ghavidel Nasim,
Fatehi Pedram
Publication year - 2020
Publication title -
chemsuschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.412
H-Index - 157
eISSN - 1864-564X
pISSN - 1864-5631
DOI - 10.1002/cssc.202000965
Subject(s) - pickering emulsion , quartz crystal microbalance , chemical engineering , adsorption , emulsion , lignin , nanoparticle , oil droplet , materials science , pulmonary surfactant , contact angle , desorption , surface energy , chemistry , organic chemistry , nanotechnology , composite material , engineering
Sulfoethylated lignin (SEKL) polymeric surfactant and sulfoethylated lignin nanoparticles (N‐SEKL) with a size of 750±50 nm are produced by using a facile green process involving a solvent‐free reaction and acidification‐based fractionation. SEKL forms a liquid‐like conventional emulsion with low viscosity that has temporary stability (5 h) at pH 7. However, N‐SEKL forms a gel‐like, motionless, and ultra‐stable Pickering emulsion through a network of interactions between N‐SEKL particles, which creates steric hindrance among the oil droplets at pH 3. The deposition of SEKL and N‐SEKL on the oil surface is monitored by a using a quartz crystal microbalance. Experimentally, the formation of emulsions at pH 7 is found to be reversible owing to the low adsorption energy Δ E of SEKL on the oil droplet (Δ E ≈15 k B T ), which is determined with the help of three‐phase contact‐angle measurements. However, the high desorption energy (Δ E ≈6.0×10 5 k B T ) of N‐SEKL makes it irreversibly adsorb on the oil droplets. SEKL is too hydrophilic to attach to the oil interface (Δ E ≈0) and thus does not facilitate emulsion formation at pH 11. Therefore, it is feasible to apply SEKL for the formulation of Pickering or non‐Pickering emulsions in the form of nanoparticles or polymeric surfactants, depending on the targeted application.