Surface Activity of ABA-Type Nonionic Oligosaccharide Surfactants

We report on the surface activity of two novel ABA-type nonionic oligosaccharide surfactants: N,N '-dodecamethylene-bismaltonamide and N,N '-dodecamethylene-bis(dextran aldonamide) (DEX-C12-DEX). Surface active properties, determined from surface tension measurements, were compared with results for AB-type counterparts containing the same hydrophobic segment, N -dodecylmaltonamide and N -dodecyl dextran aldonamide (DEX-C12). Surface tension measurements, including analysis of binary surfactant mixtures of DEX-C12 and DEX-C12-DEX show that the DEX-C12-DEX does not form micelles, but induces micelle formation of DEX-C12 at a critical total surfactant concentration and diblock mole fraction. We show the effects of oligosaccharide chain length and molecular geometry on surface activity and packing density and, with the aid of molecular models, discuss our results from the viewpoint of surfactant conformation.