Dynamics of Phase Separation and Mesophase Phase Transition in Liquid Crystal and Rigid-Rod Polymer Mixtures

液晶和刚性棒聚合物混合物中相分离和中间相相变的动力学

• 批准号: 9903519
• 负责人: Thein Kyu
• 金额: $ 28.2万
• 依托单位: University of Akron
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-07-01 至 2002-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9903519&HistoricalAwards=false
• 关键词: Dynamics; Phase; Separation; Mesophase; Transition

9903519KyuThe present proposal deals with polymer composites and electro-optical materials consisting of liquid crystals (LC) and liquid crystalline polymers (LCP). It is a well-known fact that the electro-optical performance of polymer dispersed liquid crystals (PDLC) critically depends on the morphology and dispersion of liquid crystal domains. The present proposal seeks basic understanding of the electro-optical performance of polymer dispersed liquid crystals via controlling the morphology of dispersed LX domains. Emphasis has been placed on determination of the role of thermodynamic phase diagrams of LC/polymer mixtures on the final morphology including the LC dispersion and the emerging domain size. Competition between the dynamics of phase separation and nematic ordering will be investigated as most polymer systems hardly attain an equilibrium state, particularly in the polymerization induced phase separation (PIPS). This proposal covers the experimental and theoretical elucidation of (i) dynamics of phase transitions and critical phenomena in liquid crystals and side-chain liquid crystalline (or rigid-rod) polymers, (ii) effects of chain rigidity on dynamics of phase separation in binary nematics containing side-chain and main-chain liquid crystalline polymers, (iii) competition between the kinetics of mesophase ordering and dynamics of phase separation in smectic LC/polymer blends driven by either thermal quenching or chemical reactions and (iv) phase diagrams and phase separation dynamics of nanocomposites containing rigid rod polymers. To demonstrate how the thermodynamic phase diagrams can guide the kinetic pathway for the emergence of LC domains, a kinetic model for mesophase ordering and phase separation in liquid crystal/polymer mixtures has been developed based on the time-dependent Ginzburg-Landau equation (TGDL - Model C) involving coupling between the concentration and orientational order (liquid crystal ordering) parameters. It is proposed to incorporate the Flory-Huggins (FH) theory for isotropic mixing and Maier-Saupe (MS) free energy functional for nematic ordering (or Maier-Saupe-McMillan (MSM) theory for smectic ordering) into the TDGL equation. The physical significance of all parameters pertaining to the coupled TDGL - Model C equations will be clarified and their predictive capabilities will be demonstrated. The dynamics of pattern formation will be analyzed in comparison with recent experimental observations. Recognizing the possible control of domain morphology and improved understanding of mesogenic interactions, the proposed study will be extended to nano-composites. If successful, the proposed theory would alleviate some of the problems such as the trial and error approach that leads to irreproducibility of the desired domain morphology and low yields in fabrication of PDLC films.During this decade we have witnessed an immense growth in liquid crystal based optical devices such as flat panel displays. The demand for advanced organic and polymeric electro-optical materials is expected to increase in the new millenium. This area of flat panel displays has been dominated by Far East countries, primarily Japan. It is important that the United States maintains its competitive edge through the pioneering basic research in this ever-growing and promising technology. The proposed experimental and theoretical works on liquid crystal/polymeric composites will contribute to the development of new optical devices crucial for US industries through basic scientific understanding. Another important point is that all simulation programs have been written in Visual C++ to display the emergence of LC domain morphology in live-mode with the aid of an LCD projector. Such interactive programs are useful for classroom teaching and thus should be highly beneficial in the training of future scientists and engineers in the US. This new methodology of teaching is in line with the goal of the University of Akron in attaining Carnegie Teaching Academy status.

9903519Kyuthe目前的建议涉及由液晶（LC）和液晶聚合物（LCP）组成的聚合物复合材料和电源材料。 众所周知的事实是，聚合物分散液晶（PDLC）的电流性能严重取决于液晶结构域的形态和分散。 本提案通过控制分散的LX结构域的形态来寻求对聚合物分散液晶电光性能的基本理解。 重点是确定LC/聚合物混合物的热力学相图在最终形态中的作用，包括LC色散和新兴域的大小。 由于大多数聚合物系统几乎无法达到平衡状态，尤其是在聚合诱导的相分离（PIPS）中，因此相位分离和列表有序之间的竞争将进行研究。 该提案涵盖了（i）（i）液晶和侧链液晶晶体晶体（或刚性杆）聚合物（ii）链刚性对二元相分离动力学的影响的实验和理论阐明（i）（i）（i）相变和临界现象含有侧链和主链液晶聚合物的夜生子，（iii）（iii）在晶状体LC/聚合物混合物中，在热淬灭或化学反应驱动的近距离/聚合物混合物中的中循环动力学与相位分离的动力学之间的竞争含有刚性杆聚合物的纳米复合材料的分离动力学。 为了证明热力学相图如何指导LC结构域出现的动力学途径，基于时间依赖性的Ginzburg-Landau方程（TGDL--- TGDL--- c）涉及浓度和取向顺序（液晶有序）参数之间的耦合。 提议将各向同性混合的弗洛里·霍金斯（FH）理论纳入列表秩序（或Maier-Saupe-mcmillan（MSM）理论）的Maier-Saupe（MS）自由能功能，以进行TDGL方程。将阐明与耦合TDGL -C方程有关的所有参数的物理意义，并将证明其预测能力。 与最近的实验观察相比，将分析模式形成的动力学。 认识到对域形态的控制可能控制并提高了对中源相互作用的理解，拟议的研究将扩展到纳米复合材料。 如果成功的话，提出的理论将减轻一些问题，例如试验和错误方法，导致所需域形态的不可重复性和PDLC膜制造中的产量低。光学设备，例如平板显示。 预计新千年对晚期有机和聚合电流材料的需求有望增加。 该区域的平板显示器主要由远东国家（主要是日本）主导。 重要的是，通过这项不断发展且有希望的技术，通过开拓性的基础研究来保持其竞争优势。 提出的关于液晶/聚合物复合材料的实验和理论作品将通过基本的科学理解为美国行业至关重要的新光学设备的发展做出贡献。 另一个重要的一点是，所有仿真程序均已在Visual C ++中编写，以在LCD投影仪的帮助下显示LC域形态的出现。 这种互动计划对于课堂教学很有用，因此在培训美国的科学家和工程师方面应该非常有益。 这种新的教学方法符合阿克伦大学获得卡内基教学学院地位的目标。