Preparation and dilute solution properties of model Gemini nonionic surfactants

摘要

Dimeric poly(ethylene oxide) surfactants (or nonionic gemini surfactants) with the structure (C_(n-2)H_(2n-3)CHCH_2 (CH_2)_6 (or Gem_nE_m),where n is the alkyl length and m 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 m=5,10,15,20,and 30.Water solubilities and cloud temperatures at 1 wt% were determined by measuring turbidity as a function of temperature.Cloud temperatures increase with m and decrease with n,as observed for conventional surfactants.For large m the cloud temperatures were all above 100 deg C.Surfactants with small m (i.e.,n=12,14,m=5 and n=20,m=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 n and small m.CMCs of mixtures with both anionic and nonionic conventional (monomeric) surfactants were well described by an ideal mixing model.