側鏈液晶聚合物之介電研究

Abstract

本研究之主要目的是以寬頻介電光譜來探討側鏈液晶聚合物之分子運動行為。本研究第一部份首先探討兩種含有(23,3S)—2—氯—3甲基戊酸(4—己烷氧基雙苯基)酯側鏈液晶之聚環氧丙烷。含有9個亞甲基間距之聚合物IP，其具有層列A相以及旋光層?c相，在介電光譜上除了玻璃轉移溫度外，遠出現Goldstone emode緩和波峰，聚合物2P含有l2個亞甲基做為間距，其在層?'A相．及層列B相中各呈現了一個緩和波峰。在第二系列中則以(2S,3S)—:2—氯—3—甲基戊酸(4—烷氧基雙苯基)酯側鏈液晶聚環氧丙烷及1—【（4—己烷基苯）偶氮】—4'—硝基苯側鏈之環氧丙烷，此兩種含偶氮染料在介電光譜上，出現了α、β、γ及δ緩和波峰，除了玻璃轉移溫度轉移（α 緩和）外，β和γ緩和則分別為偶氮及間距分子旋轉所造成，δ緩和則是由側鏈液晶繞著主鏈旋轉所造成。 本研究第二部份合成了含有4—己烷氧基—4'—氰基聯苯液晶基之側鏈液晶聚甲基丙烯酸酯5P，共聚甲基丙烯酸酯6P∼8P，聚丙烯酸酯9P，和共聚丙烯酸酯10P∼12P。其中共聚甲基丙烯酸酯6P∼8P則分別含有74.1、39.6及17.1莫耳％的側鏈液晶團基，而共聚丙烯酸酯10P∼12P則分別含有75.3、48.6及26.7莫耳％的側鏈液晶團基。聚合物5P和6P具有SA和N液晶相，5P其介電光譜出現了五個緩和波峰，除了玻璃轉移點（α緩和）及G-SA相轉移波峰外，另外三個是β、γ和δ緩和，其中β緩和係由柔軟間距醚基所造成，γ緩和係由氰基旋轉所造成，δ緩和是由整個側鏈液晶基繞著主鏈旋轉所造成，而6P則具有α、β、γ和δ四個緩和波峰。聚合物7P和8P不具液晶相，其介電光譜則只出現α、γ和δ四個緩和波峰，聚合物9P和1OP呈現SA和N液晶相，而聚合物11P和12P則不具液晶相，然而聚合物9P∼12P之介電光譜則皆亦呈現α、β、γ和δ四個緩和波峰，其中β緩和大部份情形皆和α緩和重疊，只有在聚合物10P時，可以明顯看出β緩和波峰。

Broad band dielectric spectroscopy has been used to investigate the molecular dynamics of side-chain hquid crystaljine(LC) polymers. In the first part of this study, two side-chain LC polyoxetane containing 4-alkanyloxy biphenyl-4'-yl(2S, 3S)-2-chloro-3-methylvalerate side group are measured. Polymer 1P which contains 9 methylene units in the spacers, reveals Sc* and SA phase and shows a Goldstone mode relaxation besides the glass transition in the dielectric spectra. Polymer 2P which contains 12 methylene units in the spacers, reveals SA and SB phases and presents two relaxation peaks besides the glass transition in the dielectric spectra. The second series of copolyoxetanes containing 4-hexoxybiphenyl-4'-yl (2S,3S)-2-chloro-3-methylvalerate and 1-[(4-hexoxyphenyl)azo]-4-nitro benzene side groups. Both dye containing LC copolyoxetanes reveals α、β、γand δ relaxations in the dielectric spectra. Besides the glass transition (α relaxation), β and γ relaxations belong to the huldered rotations of azo and ether group in the side chains, and δ relaxation is attributed to the rotation of the LC side groups around the main-chains. The second part of this study, polymetbacrylate(5P), copolymethacrylates (6P∼8P), polyacrylate(9P), copolymethacrylates(1OP∼12P) containmg 4-hexoxy-4'-cyanobiphenyl side groups are prepared and characterized. Copolymethacrylates 6P∼8P contain 4.1, 38.7 and 17.1 mole % of 4-hexoxy-4'-cyanobiphenyl side group. Polymers 5P and 6P reveal SA and N phases. Polymer 5P shows five relaxatior peaks in the dielectric spectra, beside the glass transition (α relaxation) and glassy-SA transition, it present a β relaxation which is attributed to the rotation of the ether group of spacer, a γ relaxation which belongs to hindered rotation of cyano group, and a δ relaxation which is attributed to the rotation of the LC side groups around the main-chain. Polymer 6P reveals α、β、γ and δ relaxations in the dielectric spectra. Polymers 7P and 8P show no mesomorphic behavior and reveal only α、β、γ and δ relaxations in the dielectric spectra. Both polymers 9P and 10P present SA and nematic phases while polymer 11P and 12P show no mesomolphic behavior. All of polymers 9P∼12P reveal also α、β、γ and δ relaxations in the dielectric spectra. In the most of the cases, the β relaxation is overlapped with α relaxation and is observed only in the dielectric spectrum of 10P.