ABSTRACT
As a simple example of an autonomous motor, the characteristic features of self-motion coupled with the acid-base reaction were numerically and experimentally investigated at the air/aqueous interface. Oscillatory and uniform motion were categorized as a function of the reaction order by numerical computations using a mathematical model that incorporates both the distribution of the surface active layer developed from a material particle as the driving force and the kinetics of the acid-base reaction. The nature of the self-motion was experimentally observed for a boat adhered to a camphor derivative with a mono- or di-carboxylic acid on a phosphate aqueous phase as the base.
Subject(s)
Models, Chemical , Motion , Camphor/chemistry , Carboxylic Acids/chemistry , Hydrogen-Ion Concentration , KineticsABSTRACT
Control of the self-motion of a camphanic acid disk on water was investigated upon the addition of different kinds of surfactants (Triton X-100 and Brij58 as neutral surfactants, cetyltrimethylammonium bromide (CTAB) as a cationic surfactant, and sodium dodecyl sulfate (SDS) as an anionic surfactant) to the water phase. With an increase in the concentration of surfactant, continuous motion changed to no motion via intermittent motion (repetition between motion and rest), and the concentration regions of these motions were different among these surfactants. Although the concentration regions of these motions were determined by the surface tension for neutral surfactants, they were different than those for CTAB and SDS. These characteristics of self-motion are discussed in relation to the surface tension, depending on the concentration of individual surfactants, and the hydrophilic effect of the surfactants.
Subject(s)
Bridged-Ring Compounds/chemistry , Lactones/chemistry , Surface-Active Agents/chemistry , Cetrimonium , Cetrimonium Compounds , Motion , Octoxynol , Sodium Dodecyl Sulfate , Static Electricity , Surface Tension , WaterABSTRACT
As a simple autonomous motor, the self-motion of a camphanic acid disk on the aqueous phase with a neutral surfactant (Triton X-100) was investigated. Whereas only continuous motion was observed on water, intermittent motion (alternating between motion and rest) was observed upon addition of Triton X-100. Under the experimental conditions that gave intermittent motion, the surface tension of the aqueous phase changed periodically, synchronous with the contact angle around the camphanic acid disk. These characteristics of self-motion are discussed in relation to the surface tension depending on the concentration of camphanic acid with or without Triton X-100 as the driving force of the motion.
