| Summary: | 碩士 === 國立成功大學 === 化學工程學系碩博士班 === 94 === In this study, the surface hydrophobicity of silica particles was controlled through surface modification by butanol, octanol, and hexadecanol, respectively. The Langmuir layer behavior and Langmuir-Blodgett (LB) film morphology of the mixed silica particle/poly(dimethylsiloxane) (PDMS) systems were then investigated.
Experimental results demonstrated that for the mixed Langmuir layer of PDMS and silica particles with surface modification by butanol, the surface pressure-area per particle isotherm shifted to the left in comparison with that of a silica particle Langmuir layer. This probably resulted from a loss of particles during the compression stage due to the less hydrophobic characteristic of the silica particle surface. Strong hydrophobic surface characteristic was found for silica particles with surface modification by octanol or hexadecanol. For the mixed Langmuir layer of PDMS with the more hydrophobic silica particles, the lift-off point of the isotherm shifted to the right in the presence of PDMS.
The Langmuir layers at the air/liquid interface were transferred onto glass substrates by the Langmuir-Blogett (LB) deposition technique, and the LB films were analyzed by scanning electron microscopy (SEM). It was found that a mixed C4H9-SiO2/PDMS LB film with a high surface coverage could be fabricated on a glass substrate. Since only a weak interaction was available between particles, no phase separation occurred in the mixed Langmuir layer. For the mixed C8H17-SiO2/PDMS system, strong interactions between particles might result in phase separation in the mixed layer with the PDMS expulsion during the compression stage, and a LB film with more holes was obtained. The surface morphology of a mixed C16H33-SiO2/PDMS LB film was similar to that of a C16H33-SiO2 LB film. It appeared that a phase separation occurred in the mixed Langmuir layer and PDMS molecules aggregated around the inhomogeneous structures of the C16H33-SiO2 layer when they were expelled from the air/liquid interface.
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