ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
Multicomponent surfactant system, sodium dodecyl sulfate and butanol in an aqueous NaCl solution, which exhibits a closed-loop type reentrant phase separation, was investigated by light scattering experiments focusing on the double critical behaviors and the finite micellar size effect on the dynamic critical behavior. The loop size decreased with the decrease of NaCl concentration, and the double critical point appeared. Approaching the double critical point, the critical exponents ν for the long-range correlation length ξ and γ for the isothermal osmotic compressibility χT determined by use of the spinodal divergency theory showed a crossover behavior from Fisher's renormalized Ising model values to the doubling of them. ξ and χT formed master curves as a function of εUL=|(TU−T)(TL−T)|/TUTL, and had the effective critical exponents ν=0.73 and γ=1.41 ascertaining the validity of Fisher's renormalized Ising model. Here, TU and TL are the upper and lower critical solution temperatures, respectively. Dynamic critical behaviors were well explained in a unified manner over the hydrodynamic and critical regions by the modified dynamical droplet model taking the finite micellar size into account, which assumes that the local fluctuations activated thermally behave as the physical clusters with a fractal dimension of df=2.49 and a polydispersity exponent of τ=2.21. The evaluated monomer unit sizes are in good agreement with the micellar sizes obtained independently. © 2000 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.1288004
