## 4 Discussion
Isononyl isononanoate shows the lowest molecular weight and viscosity, while logP (increasing with decreasing polarity) does not seem to vary much compared to coco-caprylate/caprate. Depending on the oil composition of the emulsions, variations in the partial occlusive effect would be expected with the most likely contribution for E1, probably followed by E2 and E3 combining caprylic/capric triglyceride (highest viscosity and molecular weight) with other emoliments. E4, containing coco-caprylate/caprate alone (at 10% only), would be expected to bring the lowest occlusive contribution. However, E2, E3 and E4 significantly reduced the TEWL, compared to baseline and compared to the untreated area. Further investigation of the film-forming capacity through advanced scanning electron microscope observation (i.e., SEM-EEG) and characterization of the eventual film formed using the atomic force microscopy (AFM) technique could be an interesting perspective to support the hypotheses discussed. All the formulations demonstrated a significant moisturizing effect, regardless of the chosen oils phase, including one that only contains 10% of the isononyl isononanoate, which is most quickly absorbed during spreading. Microscopic examination with an optical microscope (ECLIPSE NI-U; Nikon, Tokyo, Japan) did not show significant differences between emulsions: oil droplet size ranged from 1 um to around 8 um for larger ones. Birefringent structures around the oil droplets observed under polarized light indicated the presence of lamellar liquid crystalline bilayers regardless of chosen oils phase (examples of microscopic appearance with oils having the highest and lowest molecular weight can be seen in Appendix B, Figure A2). The droplet size is relatively small compared to a previous publication in combination with a C20-C22 APG that showed a size from around 10 um to 50 um [22] and a second work with C16-C18 APG that reported a size from around 5 um to around 40 um [14]. Although C12-C20 glucolipid emulsifier was used alone and at a much lower dosage than that reported in previous publications [21; 22], the lamellar phases could play a role in the moisturizing effect. Another formulation adjustment related to the dose of rheology modifier used to ensure optimum stability of the formulation. This type of widely used polymer is not known to trigger any moisturizing effect. Polymer concentration was also reported to have no significant impact on emulsion skin capacitance containing an increasing concentration of three acrylate-based polymers [46]. In addition, in the study conducted in France, \begin{table}
\begin{tabular}{c c c c} \hline
**Ingredient (INCI Name)** & \
\begin{tabular}{c} **Average Molecular Weight** \\ **(g\(\cdot\)mol\({}^{-1}\))** \\ \end{tabular} &
\begin{tabular}{c} **Viscosity \$ at 20 \({}^{\circ}\)C** \\ **(mPa-s)** \\ \end{tabular} & **LogP \({}^{\text{h}}\)** \\ \hline Caprylic/Capric Triglyceride & 500 & 30 & 8.2–10.9 \\ Cetaaryl Ethylhexanoate & 369 & 14.5 & \textgreater{}10 \\ Coco-caprylate/caprate & 335 & 11 & 6.76–8.72 \\ Isononyl Isononanoate & 285 & 5 & 6.92–7.90 \\ \hline \end{tabular}
\end{table} 
Table 4: Emolient characteristics. the control formulation E0, containing the highest dose of oil (20%) combined with this stabilizer but without the glucolipid emulsifier, did not show any significant effect on skin capacitance, compared to the untreated area. A rapid effect was observed compared to baseline, but was no more significant after 5 h. This finding suggests that the emulsion organization provided by the glucolipid surfactant is necessary to obtain a significant moisturizing effect a few hours after application. As E1 emulsion represents the most favorable structure to a possible effect of the oil due to the highest rate of oily phase and its nature (ester with the longest fatty chain), this deduction can likely be extended to other tested formulations.