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

Abstract

The ionization of the spectroscopic probe molecule 4-heptadecyl-7-hydroxycoumarin (HHC) cast in Langmuir-Blodgett (L-B) films with the neutral diluent molecules polyvinyl octadecyl ether) (PVOE) and octadecan- l-ol (OA) has been examined via the techniques of attenuated internal reflection spectroscopy and streaming potential measurements. For the HHC/PVOE system, cast onto fused silica made hydrophobic with octadecyltrichlorosilane (OTS), the anomalous titration results obtained earlier from this laboratory were confirmed by both techniques. A detailed theoretical examination, including consideration of the possible effects of ion binding, probe aggregation, and probe-substrate interactions..