Highly Concentrated Emulsions Based on the Reverse Micellar Cubic Phase

Abstract

The phase behavior of commercial lipophilic poly(oxyethylene)-poly(dimethylsiloxane) copolymer (PEOS), Me₃SiO(Si(Me)₂O)_x-(SiMe(C₃H₆(OCH₂CH₂)_nOH)O)_ySiMe₃ (x= 50-100, y= 1-5, n= 7-15, HLB value= 5), in water and water + oil systems was investigated by phase study and small angle X-ray scattering (SAXS). The lipophilic PEOS forms a reverse hexagonal liquid crystal (H₂) phase in water, and the H₂ + excess water phase exists at a low concentration. The H₂ phase changes to a reverse micellar cubic (I₂) phase with addition of oil. The I₂ structure is identified to the Fd3m space group by SAXS. An excess water phase is also coexisted with I₂ phase beyond the solubilization limit of water in the I₂ phase and a large amount of water can be dispersed in I₂ phase as emulsion droplets. As a result, highly viscous or stable gel-emulsion over 96% water as the internal phase could be formulated.