Preparation and dilute solution properties of model gemini nonionic surfactants

Dimeric poly(ethylene oxide) surfactants (or nonionic gemini surfactants) with the structure (Cn-2H2n-3CHCH2O(CH2CH2O)(m)H)(2) (CH2)(6) (or Gem(n)E(m)), where n is the alkyl length and in is the average number of ethylene oxides per head group, were synthesized. Surfactants were synthesized with alkyl chain lengths n = 12, 14, and 20 and in = 5, 10, 15, 20, and 30. Water solubilities and cloud temperatures at I wt% were determined by measuring turbidity as a function of temperature. Cloud temperatures increase with in and decrease with n, as observed for conventional surfactants. For large in the cloud temperatures were all above 100 degreesC. Surfactants with small in (i.e., n = 12, 14, in = 5 and n = 20, in = 10) were insoluble at room temperature, forming two-phase mixtures. Critical micelle concentrations (CMCs) were measured using a pyrene fluorescence method and are all in the range of 10(-7) to 10(-6) M, with the lowest values from the surfactants with large it and small in. CMCs of mixtures with both anionic and nonionic conventional (monomeric) surfactants were well described by an ideal mixing model. (C) 2004 Elsevier Inc. All rights reserved.