Contact angle of lead stearate-covered water on mica during the deposition of Langmuir-Blodgett assemblies

Abstract

We have measured the dynamic and static contact angles between the monolayer-covered water surface and a mica substrate during the deposition of successive monolayers of lead stearate. The substrate was suspended from a Cahn RG Electrobalance in order to measure the contact angle-dependent force during deposition of the film; both dynamic and static angles were calculated from the output of the balance. The difference between the dynamic contact angles of the film- covered subphase on clean mica and during polar deposition on a lead stearate multilayer is approximately 18°. The static contact angle on the upstroke (polar deposition, StPb/PbSt) averages 6° greater than the dynamic angle. On the other hand, there is very little difference on the downstroke (PbSt/StPb deposition) between the static and the dynamic angles. The contact angles appear to be independent of surface pressure in the range 15–24 dyn cm -1.