Critical phenomenon of nonaqueous microemulsion (AOT/DMA/decane)

The critical phenomenon of nonaqueous microemulsion was studied for the first time. The coexistence curves of (T,n), (T,ϕ), and (T,ψ) (n and ϕ are refractive index and volume fraction, respectively; ψ is defined as ψ=ϕ/[ϕ+ϕc(1−ϕ)/(1−ϕc)]) for a ternary microemulsion [ϕ (AOT-DMA)+(1−ϕ) decane] at constant pressure and a constant molar ratio (ω=2.86) of DMA to AOT have been determined within about 7 K from the critical temperature Tc by measurements of refractive index. The critical exponent β has been deduced from (T,n), (T,ϕ), and (T,ψ) coexistence curves within 1 K below Tc. They all were 0.329±0.005 and were consistent with the 3D Ising value. The experimental results in a temperature range of (Tc−T)<7K also have been analyzed to obtain critical amplitudes and the Wegner correction terms, to examine the diameters of the coexistence curves.