Effect of Surfactant Molecular Structure on Emulsion Stability Investigated by Interfacial Dilatational Rheology

Abstract

Polyglycerol polyricinolate (PGPR) and polyglycerol-2 dioleate were selected as model surfactants to construct water-in-oil (W/O) emulsions, and the effect of interfacial rheological properties of surfactant film on the stability of emulsions were investigated based on the interfacial dilatational rheological method. The hydrophobicity chain of PGPR is polyricinic acid condensed from ricinic acid, and that of polyglycerol-2 dioleate is oleic acid. Their dynamic interfacial tensions in 15 cycles of interfacial compression-expansion were determined. The interfacial dilatational viscoelasticity was analyzed by amplitude scanning in the range of 1–28% amplitude and frequency sweep in the range of 5–45 mHz under 2% amplitude. It was found that PGPR could quickly reach adsorption equilibrium and form interfacial film with higher interfacial dilatational viscoelastic modulus to resist the deformation of interfacial film caused by emulsion coalescence, due to its branched chain structure and longer hydrophobic chain, and the emulsion thus presented good stability. However, polyglycerol-2 dioleate with a straight chain structure had lower interfacial tension, and it failed to resist the interfacial disturbance caused by coalescence because of its lower interfacial dilatational viscoelastic modulus, and thus the emulsion was unstable. This study reveals profound understanding of the influence of branched structure of PGPR hydrophobic chain on the interfacial film properties and the emulsion stability, providing experimental reference and theoretical guidance for future design or improvement of surfactant.

Protein nanoparticles directed cancer imaging and therapy

“…Mild conditions, without surfactants, and simple process [72] Unstable particle size [34] pH [72] Emulsification Uniform size [99] Necessary surfactants, complex preparation process [96,97] Monodisperse droplets [99] Salting out Simple and green preparation [67] Wide size distribution [102] pH [102] Spray drying Good particle dispersion, convenient operation and control, and suitable for mass production [104,106] Equipment support required [107] Surfactant concentrations and spray mesh sizes [107] Self-assembly Reversible [110] Limited scope of application pH [112] hydrophilic drugs due to the hydrophobic binding sites of albumin as well as the hydrophilic binding sites of HA [93]. The binding strength between HSA and drug is significant because it determines when the drug is released in vivo.…”

“…The basic types of emulsions include oil-in-water (O/W) and water-in-oil (W/O). Surfactants have an important influence on the process of emulsification to form an emulsion [ 96 ]. In the emulsion constituted by oil and water, the phase with a high surfactant solubility is generally the continuous phase of the emulsion.…”

Magnetic Hyperbranched Molecular Materials for Treatment of Oily Sewage Containing Polymer in Oilfield Compound Flooding

“…In addition to oil droplets, underground minerals, and solid impurities, the output sewage after oil–water separation also contains a certain amount of polymers, surfactants, and alkalis ( Li et al, 2021 ). The synergistic action of oil droplets, polymers, surfactants, and alkalis in water will form stable emulsions, even microemulsions ( Jin et al, 2021 ). The emulsion is stable in nature, difficult to break demulsification, slow to settle mechanical impurities in the water body, and difficult to flocculate ( Chen et al, 2018 ; Huang et al, 2019 ).…”

Pickering Emulsions Stabilized by Chitosan/Natural Acacia Gum Biopolymers: Effects of pH and Salt Concentrations

“…Ideally, traditional emulsions are stabilized by surfactants or by amphiphilic molecules, such as polysaccharides and proteins with sizes less than 5 nm [ 1 , 2 ]. It was Ramsden and Pickering who reported in the early 1990s an alternative approach to stabilizing emulsions by utilizing small particles in the range of 5 nm to several microns [ 1 ].…”

“…AG is commonly utilized as a stabilizer, thickener, emulsifier, surface-finishing material, and flavoring agent [ 22 ]. Just like CT, AG has also been investigated as a promising emulsifier for different types of emulsion [ 2 , 5 , 6 , 8 , 21 , 23 ]. According to the aforementioned studies, both CT and AG have been used independently as stabilizers to produce different emulsion systems.…”