Quaternary ammonium dimeric surfactant micelles in aqueous micellar behavior and characteristics
|Course||Physical and chemical|
|Keywords||Dimeric quaternary ammonium surfactants Micellization Behavior Thermodynamics Micellar properties Spacer group influence Solubilization Binary mixtures|
Dimeric surfactant is a quaternary ammonium salt by a coupling of the two ionic groups of the ionic surfactant head group coupled in chemically bonded together, which changes the \shape, which strongly influence the aggregation of surfactant molecules to form micelles, and the characteristics. This work investigated electrical conductivity method quaternary ammonium dimeric surfactant C m -sC m · 2Br (m = 8,10,12,14; s = 2, 6 and m = 12; s = 3,4) in aqueous micellar behavior, including micellization temperature effects and enthalpy / entropy compensation phenomena; summarize C m -sC m · 2Br surfactant micelle process of the main driving factors; steady-state fluorescence and Viscosity Method C 12 -sC 12 · 2Br molecule intermediate spacer group chain length (s = 2,3,4,6) aggregation behavior in aqueous solution of its impact. On this basis, the use of Moroi continuous association micelle equilibrium model (Stepwise association equilibrium model), with naphthalene, anthracene, pyrene as a model hydrophobic compounds studied by UV spectrophotometry at C 12 - sC 12 · 2Br aqueous micellar solubilization, from a thermodynamic point of view summary C 12 -sC 12 · 2Br solubilization law; simultaneously The effects of C 12 -sC 12 · 2Br micelles with naphthalene, anthracene, pyrene interactions. In addition, also inspected the C 12 -sC 12 · 2Br surfactant alkyl chains with ordinary non-ionic surfactant C 12 E n of complex behavior. C m -sC m · 2Br (m = 8,10,12; s = 2,6 and m = 12; s = 3,4) in aqueous solution micellization tendency was stronger in its \spacer group between the ionic head groups under the action closer than static equilibrium distance, thereby strengthening the hydrophobic interaction between alkyl chains. C m -sC m · 2Br aggregation mechanism and C m TABr similar, are mainly from the entropy driven. s small and m is large for C m -sC m · 2Br easy to form a stable micelle structure. C 12 -sC 12 · 2Br micellar aggregation number N C with surfactant concentration increases, which, when s = 2 when N value at C = 7.7mmol · L -1 sup> after a sharp increase, the results indicating that micelle shape has changed significantly, the formation of spheroidal micelles. Viscosity measurement results confirmed this. When C 12 -sC 12 · 2Br concentration is fixed, the aggregation number N with s increases. Naphthalene, anthracene, pyrene were solubilized in C 12 -sC (12) · 2Br micelle palisade layer area, and with the same area in the palisade layer of quaternary ammonium cations exist between the head groups - π electron interaction. Pyrene monomer and dimer forms were added Luo in s = 2 s = 3,4,6 and the micelle. C 12 -sC 12 · 2Br micellar solubilization of individual alkane chain molecules with prime micelle aggregation number is inversely proportional to illustrate a single head group corresponding alkane chains The palisade layer region of space that affect the size of solubilization of the main factors. Polycyclic aromatic hydrocarbons and the first step in the cavity regiment association equilibrium constant K 1 are with naphthalene, anthracene, pyrene order increases. C 12 -sC 12 · 2Br and non-ionic surfactant C 12 E 10 or C 12 E 23 in aqueous solution to generate mixed micelles. Its critical micelle concentration cmc T values between two yuan each component complex system critical micelle concentration cmc 1 0 sup> and cmc 2 0 sup> between. When you add a small amount of non-ionic surfactants (eg a 2 = 0.1), mixed micelles C 12 E 10 or C < sub> 12 E 23 are more than 0.35 mole fraction; With the solution of non-ionic surfactant content increases, the mixed micelles gradually to C 12 E 23 or C 12 E 23 -based ingredients.