Adsorption and Aggregation Properties of Homogeneous Polyoxypropylene–Polyoxyethylene Alkyl Ether Type Nonionic Surfactants

Homogeneous polyoxypropylene (PO)–polyoxyethylene (EO) alkyl ether type nonionic surfactants comprising alkyl, EO, and PO chains with identical chain length distributions (CnEOxPOy; alkyl chain length n = 10, 12, 14, or 16; EO chain length x = 4, 6, or 8; and PO chain length y = 1, 2, or 3) were synthesized from homogeneous polyoxyethylene alkyl ether bromide and monosodium polyoxypropylene by Williamson ether synthesis. The adsorption and aggregation properties of these surfactants were characterized (cloud point, surface tension, dynamic light scattering, small-angle X-ray scattering, polarization microscopy, and cryogenic transmission electron microscopy) and compared to those of conventional homogeneous EO alkyl ether type nonionic surfactants (CnEOx). The introduction of a PO chain to the EO terminal group of the CnEOx species lowered the cloud points, especially for x = 6. Contrary to our expectations, the CnEOxPOy surfactants adsorbed efficiently at the air/water interface, despite their complex st...