Measurement of contact angle relaxation during the deposition of Langmuir-Blodgett films of cadmium stearate and valinomycin

We studied the contact angle relaxation during the Langmuir-Blodgett deposition of cadmium stearate and valinomycin films. For cadmium, we found that the relaxation time of the receding contact angle depends strongly on the deposition type; the static value that the receding angle relaxes to depends on the concentration of Cd²⁺ ions in the subphase. For 4.0 × 10^-2 M Cd²⁺ subphase, the deposition begins and remains Y-type. However, at a lower concentration of 2.5 × 10^-3 M the deposition changes from Y- to X-type. Prior to this transition, the static receding angles for the two different Cd²⁺ concentrations are different but the relaxation times are about the same. After the transition, the relaxation process is more than 20 times faster. For valinomycin, the deposition is predominantly Z-type.