Spectroscopic and Electrokinetic Study of the pH-Dependent Ionization of Langmuir-Blodgett Films. 2

Abstract

The pH titration of the spectroscopic probe molecule 4-octadecyl oxy-1-naphthoic acid (ONA) cast in Langmuir-Blodgett films with the neutral diluent molecules polyvinyl octadecyl ether (PVOE) and eicosan-1- ol, onto hydrophobic silica, has been examined via the technique of attenuated total internal reflection spectroscopy and streaming potential measurements. The ONA molecules exhibited pronounced pH dependent aggregation when cast onto hydrophobic silica plates. Neutralization (titration from high to low pH) of charged ONA films was in agreement with the behavior predicted by the Gouy-Chapman equation. Reionization (titration from low to high pH) of the ONA molecules proceeded much more sl..