Figure 1

Coefficient of ellipticity $\overline{\rho }$ as a function of temperature for the interface between a 0.6-mM solution of CTAB and tetradecane. $\overline{\rho }$ is defined as $\mathrm{Im}(r_p/r_s)$ at the Brewster angle ${\theta }_B$, where $r_p$ and $r_s$ are the reflection coefficients for $p$- and $s$-polarized light, respectively, and ${\theta }_B$ is the angle where $\mathrm{Re}(r_p/r_s)=0$. Data were acquired with a phase modulation ellipsometer (Beaglehole Instruments, Wellington, NZ) equipped with a HeNe laser ($\lambda =633\mathrm{nm}$). CTAB (Fluka, 99%) was recrystallized 3 times from an acetone/ethanol mixture. Solutions were prepared in ultrahigh purity water (Elga UHQ). Tetradecane (Aldrich, 99%) was percolated twice through neutral alumina and stored under nitrogen. 8 ml of tetradecane was poured onto 7 ml of the CTAB solution in a 5-cm diameter Petri dish and allowed to equilibrate for several hours before measurements began. The temperature was changed at a rate of $1–2°\mathrm{C}$ per hour. The measured values of $\overline{\rho }$ have been corrected for the transmission coefficients at the alkane-air interface. Random errors lie within the data symbols. Reproducibility is to within the data symbols except at the phase transition temperature (value from an independent repeat shown with a cross). Systematic errors arising from the calibration procedure are $<5\%$.Reuse & Permissions

Figure 2

Interfacial tension $\sigma$ between tetradecane and aqueous solutions of CTAB with concentration, $c=0.6\mathrm{mM}$ (○), 0.45 mM (■), 0.3 mM (◇), 0.2 mM (▲), 0.15 mM (□), and 0.1 mM (●), as a function of temperature $T$. Data were acquired by axisymmetric drop shape analysis on tetradecane drops formed at the end of an inverted needle in solutions of CTAB (Tracker tensiometer, ITConcept, Longessaigne, France). Fresh drops were formed at each temperature and allowed to equilibrate for times of 5–30 min until the surface tension was stable. Random errors are within the data symbols.Reuse & Permissions

Figure 3

Calculated contributions to the coefficient of ellipticity $\overline{\rho }$ for the interface between a 0.6-mM CTAB solution and tetradecane (see text for model), together with experimental values (right-hand column). White bars, liquid phase; shaded bars, solid phase.Reuse & Permissions

Figure 4

Surface transition temperature $T_s$ as a function of the surface excess $\Gamma$ of CTAB at the tetradecane-water interface.Reuse & Permissions