https://scholars.lib.ntu.edu.tw/handle/123456789/62566
標題: | 向列型液晶4-n-pentyl-4’-cyanobiphenyl在具微溝槽結構的表面上之排列行為研究 Nematic liquid crystal 4-n-pentyl-4’-cyanobiphenyl alignment on micro-grooved surfaces |
作者: | 邱大任 Chiou, Da-Ren |
關鍵字: | 向列型液晶;微溝槽結構;液晶排列;Nematic liquid crystal;micro-grooved surfaces;liquid crystal alignment | 公開日期: | 2006 | 摘要: | 在本研究中,我們以軟性模板壓印法(soft embossing)製備聚亞醯胺微溝槽表面。此法提供了相當方便迅速的方式於高分子表面上製作線路圖案(pattern)。而吾人將聚亞醯胺微溝槽表面合成液晶盒(liquid crystal cell)之後發現,甚至在溝槽寬達3微米的情況之下4-n-pentyl-4’-cyanobiphenyl (5CB) 液晶分子仍舊可以沿溝槽方向呈現均勻的水平排列。而我們也發現其錨附能(anchoring energy)大於利用定向摩擦法(rubbing)所處理的表面。此外,我們也利用水平配向與垂直配向之聚亞醯胺前驅物(prepolymer)的混摻,來調整表面的親疏水性以調控液晶預傾角(pretilt angle)。 另外,我們也同樣利用軟性模板壓印法壓印二氧化矽的溶膠-凝膠前驅物(silica sol-gel precursor)以製備二氧化矽微溝槽表面。此二氧化矽微溝槽表面可誘導5CB液晶分子沿溝槽方向呈現均勻的水平排列,但其缺乏預傾角。故吾人進一步使用不同末端官能基的有機矽烷在二氧化矽微溝槽表面上形成自聚性分子膜(self-assembled monolayers, SAMs),以進行5CB液晶分子的預傾角調控。 吾人也同時觀察5CB液晶分子於具有微溝槽結構的有機矽烷自聚性分子膜表面的排列行為。我們先使用軟性模板壓印法壓印出二氧化矽微溝槽表面,接著在在二氧化矽微溝槽表面形成有機矽烷的自聚性分子膜。藉著軟性模板壓印法及具有各種不同末端官能基的有機矽烷材料,吾人可獨立地探討表面起伏(surface topography)與表面極性(surface polarity)對於液晶分子排列的影響。而藉由表面極性的調整,我們可以在固定的表面起伏與液晶種類條件下控制液晶預傾角。吾人成功地於0o到90o的區間範圍內調控了5CB液晶分子的預傾角,且經由其與水前進角的關聯,我們更進一步確定了在固定的液晶種類及表面起伏(surface topography)條件下,表面化學性質的確是影響液晶分子排列的主因。 最後,我們使用微觸印刷法(micro-contact printing)製備出具有不同化學性質的微米級圖案複合表面及具微米級圖案的聚苯胺表面。藉由交錯的表面性質,我們可控制在某特定區域內5CB液晶分子的排列。經過正交偏光顯微鏡的觀察,吾人發現5CB液晶分子在玻璃、n-phenylaminopropyltrimethoxysilane (PMTS) 自聚性分子膜及聚苯胺的表面上皆呈現水平排列,而其在octadecyltrichlorosilane (OTS) 自聚性分子膜表面上呈現垂直排列。此乃因其表面能量或表面極性的差異所造成。利用此現象,我們成功地利用微觸印刷法達成5CB液晶分子的多域(multi-domain)配向。 In this work, the soft embossing method is proposed to fabricate grating structure on polyimide surfaces. This method provides a convenient and rapid way to pattern polymer surfaces. These grating polyimide surfaces are assembled to form liquid crystal cells. It is found that the liquid crystal 4-n-pentyl-4’-cyanobiphenyl (5CB) director uniformly aligns along the groove direction even when the grating width is up to 3 μm. The anchoring energy of these grating polyimide surfaces is higher than that of the typical rubbed surfaces. We also mixed the planar alignment type polyimide prepolymer and homeotropic alignment type one to modify the surface property to successfully adjust the liquid crystal pretilt angle. The square-wave grating silica surfaces are also fabricated by soft embossing silica sol-gel precursor on glass substrates with an elastomeric polydimethylsiloxane mould. The patterned silica surface could induce the planar alignment of liquid crystal 5CB along the direction of micro-grooves but with no pretilt angle. The pretilt angle of 5CBs is adjusted from 0o to 90o by the further deposition of organosilane self-assembled monolayers with different functional end-groups on the patterned silica surfaces. Liquid crystal alignment was also investigated on the micro-grooved silica surfaces covered with organosilanes. We fabricated micro-grooved silica surfaces by soft embossing method followed by forming self-assembled monolayers (SAMs) of organosilanes on these micro-grooved silica surfaces. Using the soft embossing method and the broad range of the end-groups of the organosilanes, we could investigate the surface topography and surface polarity effects on the supported liquid crystals independently. By means of the surface polarity effects, we could control the liquid crystal pretilt angles by the modifications of surface chemical properties under fixed surface topography and liquid crystal type. We successfully adjusted the liquid crystal pretilt angle over the whole range from 0o to 90o by tuning the hydrophobicity of the surfaces. The correlations between water contact angle and liquid crystal pretilt angle further confirm that the liquid crystal pretilt angle is indeed only affected by the surface polarity under the same surface topography and liquid crystal type. Finally, we fabricated patterned chemical functionality surfaces and patterned polyaniline surfaces by micro-contact printing method. With the resulting alternative surface polarity, we can control the alignment of nematic liquid crystals 5CBs on these specific regions. It is found that 5CBs show planar alignment on glass surfaces, n-phenylaminopropyltrimethoxysilane (PMTS) SAMs and polyaniline surfaces according to the polarized optical microscopy, whereas homeotropic alignment on octadecyltrichlorosilane (OTS) SAMs. This is due to the differences of the surface energies or surface polarities between the polar SAMs as well as polyaniline and the OTS SAMs. From this viewpoint, we could make multi-domain alignment of nematic liquid crystals by micro-contact printing method. |
URI: | http://ntur.lib.ntu.edu.tw//handle/246246/52312 | 其他識別: | zh-TW |
顯示於: | 化學工程學系 |
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ntu-95-D88524017-1.pdf | 23.53 kB | Adobe PDF | 檢視/開啟 |
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