Lee Isaac C, Frank Curtis W, Yamamoto Tohru, Tseng Hsian-Rong, Flood Amar H, Stoddart J Fraser, Jeppesen Jan O
Center on Polymer Interfaces and Macromolecular Assemblies and Department of Chemical Engineering, Stanford University, Stanford, California 94305-5025, USA.
Langmuir. 2004 Jul 6;20(14):5809-28. doi: 10.1021/la0361518.
A series of amphiphilic bistable [2]rotaxanes--in which a ring-shaped component, the tetracationic cyclophane, cyclobis(paraquat-p-phenylene), has been assembled around two recognition sites, a tetrathia-fulvalene (TTF) unit and a 1,5-dioxynaphthalene (DNP) ring system, situated apart at different strategic locations within the central polyether section of an amphiphilic dumbbell component that is terminated by a hydrophobic tetraarylmethane-based stopper (near the TTF unit) at one end and by a hydrophilic tetraarylmethane-based stopper (near the DNP ring system) at the other end--has been designed and synthesized. The effects of systematic changes in the constitutions of the three ethylene glycol tails (diethylene or tetraethylene glycol) and end groups (hydroxyl or methoxyl functions) attached to the hydrophilic stoppers on Langmuir film balance and surface rheology experiments at 20 degreesC were examined to determine the monolayer stabilities and co-conformations of the [2] rotaxanes and their free dumbbell counterparts. These experiments allow us to propose a model for the rotaxane's structures at different surface pressures. All the [2]rotaxanes form stable Langmuir films. These films typically pass from a liquid-expanded region to a liquid-condensed region. The transition between the two regions was either directly observed or ascertained using film stability experiments. Film balance and surface rheology experiments showed that the addition of the tetracationic cyclophane component and hydroxyl end groups markedly increased the stabilities and viscoelasticity of the films.
一系列两亲性双稳态[2]轮烷已被设计并合成出来。在这些[2]轮烷中，一个环状组分，即四阳离子环番，环双（对苯二酚对苯撑），围绕两个识别位点组装而成，这两个识别位点分别是四硫富瓦烯（TTF）单元和1,5 - 二氧萘（DNP）环系，它们位于两亲性哑铃状组分中心聚醚段内不同的关键位置，该哑铃状组分一端由基于疏水四芳基甲烷的封端基（靠近TTF单元）终止，另一端由基于亲水四芳基甲烷的封端基（靠近DNP环系）终止。研究了连接到亲水封端基上的三个乙二醇链尾（二甘醇或四甘醇）和端基（羟基或甲氧基官能团）的组成系统变化对20℃下的朗缪尔膜天平及表面流变学实验的影响，以确定[2]轮烷及其游离哑铃状对应物的单分子层稳定性和共构象。这些实验使我们能够提出一个在不同表面压力下轮烷结构的模型。所有的[2]轮烷都形成稳定的朗缪尔膜。这些膜通常从液膜扩张区域转变为液膜凝聚区域。通过膜稳定性实验直接观察或确定了这两个区域之间的转变。膜天平及表面流变学实验表明，添加四阳离子环番组分和羟基端基显著提高了膜的稳定性和粘弹性。
