Mutual interactions between nonionic surfactants and gelatin — investigations in cubic liquid crystalline systems and micellar systems

Abstract

The mutual interactions between nonionic surfactants such as polyoxyethylene cetyl ethers (C₁₆EO _n ,n=15, 20) especially their cubic lyotropic liquid crystalline phases of typeI ₁ and polymer gelatin were investigated. The colloidal microstructure of such anI ₁-phase consisting of close-packed globular surfactant aggregates was shown by transmission electron microscopy (TEM). The diameter of the globules found by TEM correlated well with the periodic distance of about 7.5 nm obtained by small angle x-ray diffraction (SAXD). In ternary systems consisting of surfactant, gelatin, and water cubic liquid crystalline structures were also proved by polarized light microscopy, TEM, and SAXD. The polymer did not participate in the cubic structure but formed, at least in part, anisotropic spherulites. In diluted surfactant systems however, interactions between polymer and surfactants were clearly found by polarimetry. The nonionic surfactants caused an accelerated coil-helix transition of the polypeptid gelatin.