Novel Behavior in Shear Flow Orientation of Side-Chain Polymethacrylate Nematic Liquid Crystals
Novel Behavior in Shear Flow Orientation of Side-Chain Polymethacrylate Nematic Liquid Crystals
复制标题
侧链聚甲基丙烯酸酯向列液晶剪切流取向的新行为
DOI：
10.1021/ma3006763
复制
发表时间：
2012
期刊：
影响因子：
5.5
通讯作者：
& Matsuoka T.
中科院分区：
文献类型：
--
作者：
Tokita M.;Ikoma A.;Ishii T.;Kang S.;Watanabe J.;& Matsuoka T.
研究了具有相同甲氧基偶氮苯介元但具有四个(PM4MA)或六个(PM6MA)亚甲基不同间隔基的两种侧链聚甲基丙烯酸酯向列型液晶(LCS)的剪切流动取向。这两种聚合物向列型液晶显示出不同的取向行为。PM4MA沿速度方向(b方向)排列向列型引向器，而PM6MA根据剪切速率和摩尔质量将引向器指向中性(a方向)或速度梯度(c方向)方向。降低剪切速率或增加摩尔质量都会引起取向转变。这种异常的向列取向行为与波动的近晶团的存在有关，并且可以解释，如果与切变流耦合以诱导a取向的涨落具有随着主链长度增加而缩短的寿命，从而足够短，从而在切变流下被平均。
Shear flow orientation of nematic liquid crystals (LCs) has been investigated for two side-chain polymethacrylates having the same methoxyazobenzene mesogens but different spacers of either four (PM4MA) or six (PM6MA) methylene groups. These two polymer nematic LCs exhibited orientation behaviors distinct from each other. PM4MA arranged the nematic director in the velocity direction (theb-orientation), whereas PM6MA pointed the director to the neutral (thea-orientation) or velocity gradient (thec-orientation) directions depending on both shear rate and molar mass. Decreasing shear rate or increasing molar mass gave rise to an orientation transition fromatoc. Such anomalous nematic orientation behavior is related to the presence of fluctuating smectic clusters, and explainable if fluctuations, which couple to shear flow to induce thea-orientation, have a lifetime which decreases with increasing backbone chain length so as to be sufficiently short to be averaged out under shear flow.