NATURALS 57
Oil Phase (tot. 30%) Emulsifier
A Polyglyceryl-3 Oleate B Polyglyceryl-2 Isostearate
C Diisostearoyl Polyglyceryl-3 Dimer Dilinoleate
D Polyglyceryl-2 Dipolyhydroxystearate E PolyAquolTM
-OS2 5% 25% Lipophilics1
Viscosity (cPs)2
– –
7150
2550 3950
Stability
(1 month at 50ºC) Unstable Unstable
✓Stable3
Unstable ✓Stable
1 Simmondisa Chinensis (Jojoba) Seed oil, Isononyl Isononanote, Paraffinum Liquidum, Coco-Caprylate/Caprate, Magnesium Stearate 2 Brookfield, RVDV-1, SP 92, 10 rpm 3 separation after 3 months @ 25°C
PolyAquolTM -OS2
Optical microscopy analysis (600X)
Figure 4: Comparison of PolyAquol-OS2 with other polyglycerol-based emulsifiers in cold-process formulating conditions. Emulsions were made with 5% of emulsifiers added individually in a total 30% oil phase (jojoba seed oil, isononyl isononanoate, liquid paraffin, coco-caprylate/caprate and magnesium stearate) mixed with 70% water phase including 1% MgSO4
. Emulsions were made at
25°C. Stability was visually assessed (phase homogeneity or separation) after 1 month at 50°C or for longer periods at room temperature as indicated. Viscosity was measured with a Brookfield apparatus, RVDV-I Prime, Sp 92, 10 rpm. Micrographs were taken with a Motic microscope BA3110E equipped with a LED light source and a Moticam 5 (5.0 MegaPixel) camera. Magnification 600X.
particles with a similar refractive index – similar polarisability – will tend to attract each other.3
In a W/O emulsion
environment, the smaller the difference between refractive index of a water droplet and the oil phase, the smaller the attraction between two water droplets. The addition of electrolytes in the water phase will increase its refractive index to be slightly closer to that of the oil phase. Thereby, the difference in polarisability potential between water droplets and the oil phase will be less making water droplets more “comfortable” in the continuous oil phase.5 This would contribute to lower the van der Waals attraction forces between adjacent water droplets and lessen coalescence.
PolyAquolTM
3% 5% 5%
-OS2
Oil Phase (tot. 30%) Cyclomethicone 10% 10% 15%
Another action of electrolytes is to favour the adsorption density of emulsifier at the water/oil interface.6,7
The unique
composition of the polyglycerol-based emulsifier allows for electrostatic interactions between each of its components (Fig 1). Moreover, this configuration would lead to a more functional interplay between the oligomeric polyglycerol-based emulsifier and electrolytes. This action will be intensified by the ‘branched’ oligomeric molecular configuration of the polyglycerol-based emulsifier. Electrolytes could positively influence the electrostatic interaction especially between hydroxyl residues bridging the polyglycerol-based emulsifier
Lipophilics1
17% 15% 10%
1 Isodecyl Neopentanoate, Paraffinum Liquidum, Magnesium Stearate 2 Brookfield, RVDV-1, SP 92, 10 rpm
Figure 6: Compatibility of the polyglycerol-based emulsifier with silicone oils. Emulsions were made with the indicated concentration of the polyglycerol-based emulsifier in a total oil phase of 30% made of isodecyl neopentanoate, liquid paraffin, magnesium stearate and various concentrations of cyclomethicone. Emulsions were made at 25°C. Stability was visually assessed (phase homogeneity or separation) after 1 month at 50°C. Viscosity was measured with a Brookfield apparatus, RVDV-I Prime, Sp 92, 10 rpm.
June 2018
Viscosity (cPs)2
6950
11300 13150
Stability
(1 month at 50ºC) ✓Stable
✓Stable ✓Stable
Figure 5: Schematic representation of the interactions between the polyglycerol-based emulsifier and electrolytes in a W/O emulsion. Electrolytes (positively “+” and negatively “-“ charged ions) dissolved in the water phase would create an ionic environment favourable to electrostatic interactions between the polyglycerol heads. Collateral packing of the oligomeric polyglycerol-based emulsifier at the interface would reinforce the steric stabilization by preventing adjacent water droplets from coalescing.
components reducing interfacial tension. This collateral reinforcement of the oligomeric structure of the polyglycerol- based emulsifier could also play a role in steric stabilisation (Fig 5). Steric stabilisation acts a volume restriction keeping apart two neighbouring water droplets.8,9
the protruding oligomeric lipophilic chains would attract more oil phase in between water droplets repelling them away from each other. Altogether, the interplay between the polyglycerol-based emulsifier and electrolytes would help reduce coalescence and support the emulsion stability.
Compatibility with silicone oils and enhancement of silicone-emulsifier performance
The compatibility of the polyglycerol-based emulsifier has been tested in the presence of silicone oils. A stable emulsion (1 month at 50°C) could be achieved in conditions where cyclomethicone represents half of the total oil phase (Fig 6). Not only does the polyglycerol-based emulsifier work with silicone oils, it is also compatible with silicone-emulsifiers. In fact, it enhances the emulsifying properties of such emulsifiers. When tested alone, the polyglycerol-based emulsifier produced stable emulsions with the usual homogenous micro-structure (Fig 7). However, in the conditions tested, the
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