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 ( b C 7 - b C 9 EO 12 ). Similarly, homogeneous EO-type nonionic surfactants with linear double chains (C 8 -C 8 EO 12 ) and a linear single chain (C 18 EO 12 ) were used. b C 7 - b C 9 EO 12 and C 8 -C 8 EO 12 surfactants with branched hydrophobic chains or double chains increased the foam stability and suppressed the draining. Furthermore, they formed rod-like micelles, and C 18 EO 12 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 b C 7 - b C 9 EO 12 and C 8 -C 8 EO 12 , 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.