- 學位論文
側鏈膽固醇液晶於聚醯亞胺膜之接枝合成反應研究
The Graft Synthesis Reaction of Side Chain Cholesterol Liquid Crystal on Polyimide Film
摘要
傳統聚醯亞胺配向層因製作時的機械摩擦常會造成高分子碎屑殘留，導致產品出現瑕疵的問題。解決的方法可以利用液晶接枝於聚醯亞胺（PI）表面，使其具有配向特性。本研究嘗試藉由聚醯亞胺表面改質技術，探討側鏈膽固醇液晶接枝於PI 膜表面之可行途徑。本實驗製備含羥基之3,5-diaminobenzyl alcohol二胺類單體，並合成含羥基（hydroxy group）之可溶性聚醯亞胺。利用聚醯亞胺含有羥基於結構尾端的特點，藉由此官能基之H鍵容易被取代的特性，將含側鏈液晶分子之polysiloxane與PI 膜產生鍵結，達到表面化學接枝目的。經由FT-IR、DSC、TGA、SEM 及POM 進行鑑定及分析，並與一般不含羥基之芳香族聚醯亞胺高分子，相互比較其物性差異，本研究已成功的以聚醯亞胺為主鏈基材，將所合成的側鏈型液晶高分子Cholesteryl 4-（allyloxy）benzoate及Biphenyl 4-（allyloxy）benzoate以共價鍵結的方式接枝到聚亞醯胺薄膜表面。 本研究探討加入3,5-diaminobenzyl alcohol前，PMDA和ODA預聚合的時間（0，2，4hr）及3,5-diaminobenzyl alcohol於含羥基聚醯亞胺之含量（10%，5%，3.3%）對接枝率的影響。由實驗結果顯示，PMDA和ODA預聚合的時間愈少，含羥基聚醯亞胺薄膜所測定出之-OH官能基越多，而在進行接枝過程之接枝量，將隨著含羥基聚醯亞胺薄膜上-OH含量增加而增加。以含羥基聚醯亞胺為主體所合成的側鏈聚亞醯胺均具有不錯的熱安定性，Td介於361℃∼383℃之間，並發現隨著主鏈上3,5-diaminobenzyl alcohol二胺類含量愈高，Td有降低的趨勢。含羥基聚醯亞胺薄膜表面接枝側鏈在加熱後並沒有失去其液晶性，加熱到200℃時，觀察到膽固醇相的broken focal-conic組織，證實其為具有液晶性的高分子材料。由溶解度測試亦可以發現，所有含羥基及接枝後的聚醯亞胺均具可溶性，因主鏈的可撓性增加，而使得聚醯亞胺薄膜容易加工，形成品質優良符合光學要求的透明薄膜。
並列摘要
Traditionally, the preparation of alignment layer requires the machinical rubbing process, which damages the TFT array and reduces the yield. Grafting of liquid crystal on polyimide film provides an alternative means to prepare alignment layer with desired alignment characteristics without rubbing process. This research focused on the surface modification of polyimide film with side-chain cholesterol liquid crystal. In this experiment, 3,5-dinitrobenzyl alcohol, which contains hydroxy group, after reduction process to form 3,5-diaminobenzyl alcohol, was used as co-monomer to synthesiz polyimide that contain hydroxy group. Thus prepared polyimide film containing hydroxy group, in which hydrogen can be easily replaced, can form chaimcal bonding with the polysiloxane that contains side chain liquid crystal. From the analysis of FT-IR, DSC, TGA, SEM and POM, and compaired with polyimide without hydroxy group, it was demonstrated that side-chain liquid crystal, CAB and BAB, has been successfully grafted onto the PI film by covalent bond. The experimental results showed that, the time of prepolymerization of PMDA and ODA before the addition of 3,5-diaminobenzyl alcohol and the amount of 3,5-diaminobenzyl alcohol affect the density of hydroxyl groups on polyimide surface. The amount of hydroxyl group decreased with increasing prepolymerization time. The higher the amount of 3,5-diaminobenzyl alcohol, the higher the amount of hydroxy groups. The grafting density of side-chain liquid crystal increased with increasing amount of –OH groups on the surface of PI film. Polyimide containing side-chain liquid crystal showed reasonable good thermal stability. The temperature of decomposition Td is between 361℃∼383℃. However, as the amount of 3,5-diaminobenzyl alcohol on polyimide backbone increased, Td reduced. POM observation showed that when the grafted PI film was heated to 200℃, there is a broken focal-conic organization of cholesteric phase, indicating that the grafted side-chain cholesterol maintained its liquid crystal characterics after surface modification process. It was also found that the solubility of liquid crystal modified PI film has better solubility in various organic solvents than non-modified PI film. This is also beneficial for the processing of PI alignment layer.