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.
Nieh
Mu-Ping
MP
Neutron Program for Material Research, National Research Council, Chalk River Laboratory, Chalk River, Ontario, Canada K0J 1J0.
Kumar
Sanat K
SK
Fernando
Raymond H
RH
Colby
Ralph H
RH
Katsaras
John
J
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