Rheo-optical properties of silicone oil emulsions in the presence of polymer emulsifiers

Oil-in-Water Emulsions Stabilized by Hydrophilic Homopolymers

Most of the polymeric emulsifiers have diblock and triblock copolymer architecture containing hydrophilic and hydrophobic domains. In this work, we show that hydrophilic homopolymers can be effective stabilizers of oil-in-water emulsions. Using polyethelyne oxide and poly(vinylpyrrolidone) as model hydrophilic homopolymers and n-decane and n-hexane as model nonpolar phases, we show that high-molecular weight polymers can stabilize emulsions over 24 h beyond a threshold concentration. We highlight the role of the molecular weight and concentration of the polymer in the stability of emulsions through kinetic measurements of emulsion volume, microscopic analysis, interfacial tension, and dilational rheology. We explain the mechanism of stabilization to stem from buoyancy-driven creaming of emulsion drops and film drainage and dilational elasticity of the interface in relation to the molecular weights and concentrations of polymers. This study demonstrates that water-soluble homopolymers can stabilize oil-in-water emulsions and open avenues for the use of eco-friendly biopolymers, which are inherently hydrophilic, as an alternative to synthetic emulsifiers.

Highly stable, electrostatically attractive silicone nanoemulsions produced by interfacial assembly of amphiphilic triblock copolymers

This article presents a useful and promising approach for fabricating extremely stable silicone oil nanoemulsions, whose liquid-liquid interface is structured with a thin film of amphiphilic triblock copolymers. For this, two types of amphiphilic triblock polymer, poly(2-methacryloyloxy ethyl phosphorylcholine)-block-poly(ε-caprolactone)-block-poly(2-methacryloyloxy ethyl phosphorylcholine) (PMPC-PCL-PMPC) and poly(2-aminoethyl methacrylate)-block-poly(ε-caprolactone)-block-poly(2-aminoethyl methacrylate) (PAMA-PCL-PAMA), were synthesized by atom transfer radical polymerization. Employing the phase separation technique was critical for the formation of thin polymer interfaces, of less than 10 nm, thus eventually producing structurally stable silicone oil nanoemulsions. The co-assembly of PAMA-PCL-PAMA with PMPC-PCL-PMPC enabled the patching of positive charges on the surface of the emulsion drops. We show that these charged silicone oil nanoemulsions could be used to form a multilayer emulsion thin film by layer-by-layer deposition. Finally, we experimentally demonstrate that the silicone oil nanoemulsions fabricated in this way were highly stable and had the ability to electrostatically interact with hair, which enabled complete coating of the hair surface with a layer of silicone oil.

Silicone oil emulsions stabilized by polymers and solid particles

Silicone oil emulsions stabilized by various emulsifiers such as polymers, solid particles alone, and solid particles with pre-adsorbed surfactants or polymers are reviewed, focusing on their emulsion stability and rheological properties as a function of the emulsifier concentration. An increase in the concentration of the emulsifier leads to a decrease in the droplet size and an increase in the emulsion stability, irrespective of the emulsifier. Moreover, the overlapping concentration of polymer can be regarded as a criterion for the preparation of emulsions using polymeric emulsifiers. Changes in the emulsion stability and rheological responses of the emulsions prepared by the solid particles with pre-adsorbed polymers are discussed in terms of the amounts of the emulsifiers adsorbed. For emulsions prepared from hydrophilic silica particles with pre-adsorbed polymers, a decrease in the droplet size of an order of magnitude can be controlled by an increase in the concentration of polymer, whereas hydrophilic silica particles alone cannot produce stable silicone oil emulsions.

Silicone oil emulsions: strategies to improve their stability and applications in hair care products

Silicone oils have wide range of applications in personal care products due to their unique properties of high lubricity, non-toxicity, excessive spreading and film formation. They are usually employed in the form of emulsions due to their inert nature. Until now, different conventional emulsification techniques have been developed and applied to prepare silicone oil emulsions. The size and uniformity of emulsions showed important influence on stability of droplets, which further affect the application performance. Therefore, various strategies were developed to improve the stability as well as application performance of silicone oil emulsions. In this review, we highlight different factors influencing the stability of silicone oil emulsions and explain various strategies to overcome the stability problems. In addition, the silicone deposition on the surface of hair substrates and different approaches to increase their deposition are also discussed in detail.

Emulsion intercalation of smectite clays with comb-branched copolymers consisting of multiple quaternary amine salts and a poly(styrene-butadiene-styrene) backbone

Layered silicates were intercalated with comb-branched copolymers consisting of a hydrophobic polystyrene-b-poly(ethylene/butylene)-b-polystyrene (SEBS) backbone and multiple pendants of poly(oxyalkylene) (POA) quaternary ammonium salts. The requisite intercalating agents were synthesized by grafting POA amines on the maleated SEBS. The corresponding SEBS-POA amine salts were found to have two functions, the capability to emulsify toluene/water mixtures to fine particle sizes of 60-70 nm in diameter and to exchange ions with sodium montmorillonite. The resulting silicate hybrids were characterized by X-ray diffraction and transmission electron microscopy. Two types of intercalations with silicate d spacing of 18 and 50 A were obtained, in which the dissimilarity is attributed to disparate polymer incorporations, POA pendants only or the combination of both the SEBS backbone and POA in the gallery. Furthermore, the two conformations of polymer-intercalated silicates are reversibly transformable by varying emulsion conditions, micelle sizes, and solvents.