Characterization of the Solutol® HS15/water phase diagram and the impact of the Δ9-tetrahydrocannabinol solubilization

Here, the phase behavior of the commercial non-ionic surfactant Solutol® HS15 in water was investigated. The focus was on the evolution of the system nanostructure at low water content. Particularly, it was demonstrated that spherical micelles found in dilute surfactant solutions coalesce at a surfactant volume fraction close to 0.5. As consequence, a heterogeneous pseudo-binary mixture occurs. No liquid crystalline phases were detected even at the highest HS15 concentrations in water. Alteration of the micellar morphology induced by the addition of Δ9-tetrahydrocannabinol to the surfactant/water binary system was also investigated. It was found that the cannabinoid molecules become entrapped within the surfactant hydrophobic tails, thus increasing the surfactant effective packing parameter and inducing a radical change of the micelle shape. At sufficiently low water content (18–35 wt.%), such alteration of the interfacial packing results in a lamellar organization of the surfactant molecules.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (117 K)Download as PowerPoint slideHighlights► The phase behavior of the surfactant Solutol HS15 in water was investigated. ► At low water content, spherical micelles are present. ► Micelles coalesce at a surfactant volume fraction close to 0.5. ► A morphological change of the micelles occurred on addition of the cannabinoid THC. ► THC entraps within the surfactant tails modifying the micelle shape.