Molecular Architecture Studied by the Surface Forces Measurement.

This feature article reviews the surface forces measurement as a tool for studying molecular architecture chemistry. The history of the measurement is briefly described in the Introduction. The general overview covers specific features of the surface forces measurement as a tool for studying and using molecular architecture. This measurement is powerful for understanding interaction forces and for characterizing and discovering the phenomena at solid-liquid interfaces and soft complex matter. An apparatus for opaque samples was developed, which can be used to study not only opaque samples in various media but also electrochemical processes under various electrochemical potentials. Our studies of molecular architecture are reviewed; they include biological molecular recognition especially involved in the enzyme-substrate interaction; polyelectrolyte brushes exhibiting steric repulsion, which can be reproduced by the osmotic pressure of the counterions, and a density-dependent transition; the hydrogen-bonded molecular macrocluster formation of alcohol and carboxylic acids adsorbed on silica in nonpolar solvents such as cyclohexane; and surface forces between ferrocene-modified electrodes under various applied potentials. These studies demonstrate how the forces measurement is used to identify interacting species such as in biological systems to reveal unknown phenomena and to characterize soft complex matter and the effective potential of the electrodes. Readers will be introduced to the broad applications of the force measurement.