Structure and Interfacial Energy Control by Semifluorinated Polymers, as a Mechanistic Tool to Orient Liquid Crystals

该奖项旨在发展一类新型半氟化聚合物的分子结构与其界面结构和能量之间的关系。从长远来看，它试图测试这些聚合物作为液晶薄膜定向支撑层的潜力。这将使用一种新型含氟聚合物，其主链上有一个介生基团（即液晶分子）-甲基二苯乙烯，由全氟环丁基环（PFCB）桥接。桥接基团用于控制聚合物的表面能和柔韧性。原子力显微镜（AFM），偏振光学显微镜，接触角测量，x射线/中子散射和反射率将被使用。对于任何基于液晶的设备，液晶分子必须与表面对齐，然而，它们必须快速响应，对外部刺激没有任何记忆效应。两个相反的因素，表面方向和微弱的方位角锚定之间需要一个微妙的平衡。这个问题的重要性体现在大量的研究中，这些研究都涉及到这个问题。在过去的十年中，氟作为表面锚定的改性剂被引入。在本研究中，我们建议利用聚合物的化学结构来构建定向层。它们的表面相互作用将完全取决于聚合物的性质，无需进一步的外部处理。聚合物的设计包括纳入介生基团，或类似的化学骨架，其有望作为诱导有序的“成核位点”，由一个可以修改聚合物表面能以改变锚定能的基团桥接。包括差示扫描量热法、x射线散射核磁共振和偏振光学显微镜在内的标准技术将用于表征新合成聚合物的总体性质。然后将薄膜浇铸在不同的支架上，并通过原子力显微镜、偏振光显微镜、接触角测量、x射线/中子散射和反射率来研究它们的结构和表面能。随着能量控制界面的形成；将形成具有良好表征的液晶分子的复合材料。将研究LC在聚合物层上的取向及其对电刺激的响应。本研究的意义在于对聚合物界面特性的基本认识及其与液晶界面排列的相关性，从而带来深远的技术应用，从新的快速响应LC器件到光波导和新型光纤。

This award seeks to develop the relationship between the molecular structure of a novel class of semifluorinated polymers, and their interfacial structure and energies. Long term it seeks to test the potential of these polymers as support layers to orient liquid crystal thin films. This will be attained using a novel fluoropolymer with a mesogenic group (i.e. liquid crystal molecule), beta-methylstilbene on its backbone bridged by a perfluorocyclobutyl ring (PFCB). The bridging groups are used to control the surface energy and flexibility of the polymer. Atomic Force Microscopy (AFM), polarized optical microscopy, contact angle measurements, and X-ray/neutron scattering and reflectivity will be used. For any liquid crystal based device, the liquid crystal molecules have to be aligned by the surface, however, the have to respond quickly, without any memory effects to an external stimuli. A delicate balance between two opposing factors, surface orientation and weak azimuthal anchoring is requires. The significance of the problem is manifested in the large number of studies, which address the issue. In the last 10 years fluorine has been introduced as a modifier for the surface anchoring. In the present study we propose to utilize the chemical structure of a polymer confined to construct orienting layers. Their surface interactions will depend solely on the nature of the polymer with no further external treatments. The design of the polymer includes incorporating a mesogenic group, or similar chemical backbone, which are expected to serve as a "nucleation site" for inducing ordering, bridged by a group that can modify the surface energy of the polymer to alter the anchoring energy. Standard techniques including differential scanning calorimetry X-ray scattering NMR and polarized optical microscopy will be utilized to characterize the bulk properties of the newly synthesized polymers. Films will then be cast on different supports and will be studied by atomic force Microscopy polarized optical microscopy, contact angle measurements, and X-ray/neutron scattering and reflectivity, to study their structure and surface energies. Following the formation of the energy controlled interfaces; composites with well-characterized liquid crystalline molecules will be formed. The orientation of the LC cast on the polymer layers and its response to electrical stimuli will be studied.The significance of the proposed research lies in the basic understanding of interfacial characteristics of polymers and its correlation with interfacial alignment of liquid crystals leading to far-reaching technological applications, ranging from new fast responding LC devices, to optical wave-guides and new fiber optics.