Stability and Structural Analysis Using Small-Angle Neutron Scattering for Foam of Homogeneous Polyoxyethylene-Type Nonionic Surfactants with Multibranched Chains.

Small-angle neutron scattering can provide insight into the microstructure of the surfactant-stabilized foam. In this study, small-angle neutron scattering in combination with other techniques was employed to determine the microstructure of the foams stabilized using novel homogeneous polyoxyethylene (EO) alkyl ether-type nonionic surfactants with multibranched double chains (C-CEO). Similarly, homogeneous EO-type nonionic surfactants with linear double chains (C-CEO) and a linear single chain (CEO) were used. C-CEO and C-CEO surfactants with branched hydrophobic chains or double chains increased the foam stability and suppressed the draining. Furthermore, they formed rod-like micelles, and CEO formed spherical micelles in the bulk solution. The foam film containing the plateau border contained micelles identical with those found in the bulk solution. For C-CEO and C-CEO, the average radius of the bubbles immediately after foaming was of the order of hundreds of μm. Finally, these radii grew to the order of thousands of μm. Thus, a significant correlation was observed between the micellar structure and the stability of these foams.