| Research Abstract |
Both investigations of the AFM observation of silica plate hydrophobilized by various methods and the simulation of same system are carried out and following things are obtained.
As a result of in-situ observation of the surface hydrophobilized by the reaction with a coupling agent in water using AFM, a domain with a height of about 50nm is found out on the surface. Also, simultaneously a phase image, which shows the interaction differs from the circumference in the corresponding place, is obtained. The domain size increases and whole coverage also increased as surface hydrophobicity becomes high. When surface roughness is large, though the number of the domain adsorbed increases, each size decreases and whole coverage also decreases. Then, those domains are identified as air bubbles.
Moreover, also for the attraction between hydrophobic surfaces created by adsorption of surfactant molecules, the unique feature such that long-range and the existence of a discontinuous point is found out.
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This feature is similar with the attraction at the time of using a coupling agent, and it is suggested that the trace amount of gaseous phase existing in a system has important influence to the appearance of the attractive force.
On the other hand in the simulation, using various L-J type interaction centers, water molecules, dissolved inactive gas molecules and surfactant molecules are modeled. Using this model, the programs of MD method and MC method to calculate interaction forces are developed, and various systems are examined. Consequently, similar results to the case of AFM measurement, that is, attraction with a discontinuous point are obtained and the reason of these phenomena, being based on the bridging generated by the union of concentrated gas layer existing near the surfaces, is found out. However, gravitation generating distance is at most 2nm very small compared with measured value (several 100nm), it is necessary to take the influence of surface roughness into consideration from now on, for example. Moreover, adsorption of the surfactant on the surface is simulated and the surface fine structure is investigated. The results suggested that it is necessary to setup larger surface area than this simulation to coincide the simulation results with the AFM measurement. Less
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