含長碳鏈側取代基之可溶性聚醯亞胺之合成與鑑定

Abstract

本研究合成了二系列含長碳鏈取代基之可溶性聚醯亞胺，分別導入烷苯氧基與烷苯酯基側鏈，以提高其溶解度。第一系列聚醯亞胺(簡稱nPOF)係由 hexafluoroisopropylidenediphthalic anhydride 與 4-(4-烷基苯氧基)-1,3-二胺基苯進行縮和聚合反應而得，第二系列聚醯亞胺(簡稱nPEF)，係由 hexafluoroisopropylidene diphthalic anhydride 與4-(4-烷基苯基)-3,5-二胺基苯甲酯進行縮和聚合反應而得，其中烷基分別含有 3, 5, 6, 9, 及 12 個碳，本研究將探討烷基長度對於所合成聚醯亞胺之玻璃轉移溫度、熱安定性及溶解度之影響。 第一系列聚醯亞胺 3POF ~ 12POF 中，玻璃轉移溫度 (Tg)比無烷基取代之 POF 降低了 45 ~ 100℃ ，而分解溫度雖由 POF 的516.0℃ 降至 440 ~ 480 ℃ ，但仍比純粹導入烷基側鏈來得高。第二系列含酯基側鏈聚醯亞胺 3PEF ~ 12PEF 中，其 Tg 介於 210 ~260℃ 之間，且隨著碳鏈的增長而降低，熱分解溫度則在 413 ~ 422 ℃ 之間。兩系列的側鏈型聚醯亞胺經由 X-射線繞射鑑定，均為無定型聚合物，溶解度相當好，皆可溶於一般的有機溶劑如四氫夫喃、氯仿、甲基乙基酮、及丙酮之中，比起無側鏈取代之相似聚亞醯胺都有明顯的改善。研究結果顯示導入長烷基苯取代基於聚醯亞胺側鏈，可以有效的改善聚醯亞胺的溶解度及降低其玻璃轉移溫度，並且維持聚醯亞胺的耐高溫特性。所合成的側鏈聚聚合物皆以旋轉旋轉塗佈法成膜後經摩擦配向製成平行排列之液晶盒，探討其作為LCD 配向材料的可行性。

Two series of soluble polyimides (PI) containing long alkyl side groupsare prepared. The alkylphenoxy and alkylphenyl ester substituents are introduced into the polyimide backbone so as to improve their solubility. Thefirst series of polyimides (abbriviation nPOF) are prepared by polycondensationof hexafluoroisopropylidene diphthalic anhydride and 4-(4-alkylphenoxy)-1,3-phenylenediamine. The second series of polyimides (abbreviation nPEF) areprepared by polyocndensation of hexafluoroisopropylide diphthalic anhydrideand 4-alkylphenyl 1,3-diaminobenzoate. The alkyl groups which containsrespectively 3, 5, 6, 9, and 12 carbons are used as the long side chains. Theeffects of alkyl chain length on the glass transition, thermal stability andsolubility of the obtained poyimides are studied. The first series of polyimides (nPOF) show glass transitions intemperature range of 176 ~ 230℃, which is 40 ~ 100 ℃ lower than that of thecorresponding polyimide without a 4-alkylphenoxy side group. Their thermaldecompositions are in the temperature range 440 ~ 480 ℃. The second series ofpolyimide nPEF reveal glass transitions in the temperature range of 210 ~ 260℃ and thermal decomposition temperature in the temperature of 413 ~ 422 ℃.The results demonstrate that introducing a long alkyl side chain into thepolyimide backbone decreases dramastically the glass transition of the obtainedpolyimide. However, both series of polyimides still present pretty good thermalstability.The X-ray diffraction measurements verify that both series ofpoyimides are amorphous in nature. All of the obtained polyimides are solublein THF, chloroform, methylethyl ketone and acetone. Apparently, they show muchbetter solubility than their corresponding polyimide without the alkylphenoxyside groups. Finally, the synthesized polyimides are evaluated as alignmentmaterials for liquid crystal display. They are spin-coated onto a ITO glass andruubed with a nylon cloth after curing at 100℃. The effect of side chains onthe pretilt angle of the LC cells are discussed.