| Summary: | 博士 === 國立中山大學 === 光電工程學系研究所 === 103 === Controlling arrangement of liquid crystals plays an important role in
manufacturing LC devices. Rubbing polyimide surface which can drive LC molecules
to form uniform arrangement is the conventional way to achieve this goal. The grooved
structures of polyimide surface caused by rubbing process is regarded as the one
mechanism to arrange LC molecules. Therefore, many researches concerning to the
effect of surface topological structures to arrangement of LC molecules have been
proposed.
Polydimethylsiloxane, a silicon-based polymer, is a transparent, flexible and
environment friendly material. Besides, the stable physico-chemical properties makes
it be popular in many applied area. According to our past studies, nematic liquid crystal
molecules can be driven to form homeotropic alignment on polydimethylsiloxane plate
surface. Based on the results, PDMS confinement walls are built to confine liquid
crystals. The arrangement of liquid crystals will be affect by the four PDMS boundaries.
Through varying the depth to width aspect ratio of PDMS confinement structure, the
effect of boundaries of PDMS surfaces will be changed. That is, the arrangement mode
of liquid crystals will be changed.
In this study, imprinting method is involved to produce the PDMS confinement
structure. And we find that the arrangement of calamitic nematic liquid crystals will be
affected by means of varying the depth to width aspect ratio of PDMS confinement.
The aspect ratio is a key factor to obtain different LC arrangement. That is, nematic
liquid crystals favor to form planar arrangement as the larger aspect ratio which is
greater than 0.4. Otherwise, smaller aspect ratio would make liquid crystals to form
vertical arrangement. And for discotic liquid crystals, the PDMS confinement structure
can drive the discotic mesogens to form uniform planar arrangement.
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