Effect of the hydrophilic size on the structural phases of aqueous nonionic gemini surfactant solutions.
Aggregate structures of aqueous nonionic Gemini surfactant solutions, alpha,alpha'-[2,4,7,9-tetramethyl-5-decyne-4,7-diyl]bis[omega-hydroxyl-polyoxyethylene] with three different length polyoxyethylenes (i.e., 10, 20, and 30 ethylene oxide monomers, denoted from now on as S-10, S-20, and S-30, respectively), are investigated using small angle neutron scattering, dynamic light scattering, and fluorescence spectroscopy. For S-10 at low surfactant concentrations (Cs < 0.9 wt %), large "clusters", with an average hydrodynamic radius (RH) > 40 nm, are found to coexist with monomers. At intermediate Cs (0.9 < Cs < 2 wt %), some clusters break down forming micelles, with an (RH) approximately 2-3 nm, while the remaining clusters coexist with micelles. Increasing Cs further (>2 wt %) results in a pure micellar phase with little or no clusters present. S-20 and S-30 mixtures, on the other hand, differ from S-10 in that irrespective of surfactant concentration, large clusters and small monomers/dimers are found to coexist, while there is no direct evidence for the presence of micelles.
Neutron Program for Material Research, National Research Council, Chalk River Laboratory, Chalk River, Ontario, Canada K0J 1J0.
Mu-Ping
MP
Nieh
Sanat K
SK
Kumar
Raymond H
RH
Fernando
Ralph H
RH
Colby
John
J
Katsaras
D008027:Light; D008823:Micelles; D033363:Neutron Diffraction / Q000379:methods; D010316:Particle Size; D011092:Polyethylene Glycols / Q000737:chemistry*; D012542:Scattering, Radiation; D012680:Sensitivity and Specificity; D012996:Solutions / Q000737:chemistry; D013050:Spectrometry, Fluorescence / Q000379:methods; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry*; D014867:Water / Q000737:chemistry
D008823:Micelles; D012996:Solutions; D013501:Surface-Active Agents; C509666:alpha,alpha'-(2,4,7,9-tetramethyl-5-decyne-4,7-diyl)bis(omega-hydroxyl-polyoxyethylene); D014867:Water; D011092:Polyethylene Glycols