Spatio-Temporal Emergence of Morphological Patterns in Liquid Crystalline Polymer and Rigid-Rod Polymer Systems during Solidification

液晶聚合物和刚性棒聚合物体系在凝固过程中形态模式的时空出现

• 批准号: 0209272
• 负责人: Thein Kyu
• 金额: $ 30万
• 依托单位: University of Akron
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-07-01 至 2005-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0209272&HistoricalAwards=false
• 关键词: Spatio; Temporal; Emergence; Morphological; Patterns

The present proposal entails experimental and theoretical elucidation of (i) dynamics of hollow fiber (or nano-tube) formation during solidification of main chain liquid crystalline polymers (MCLCP) and/or rigid-rod polymer solution, (ii) dynamics of nano-porous membranes of monomeric mesognes during pattern polymerization, (iii) dynamics of microfibril formation during dry-jet spinning, and (iv) hybrid-composites. The well-established time-dependent Ginzburg-Landau TDGL (Model C) will be applied in conjunction with the advection term for the tracking of solvent evaporation and flow. The physical significanace of all parameters pertaining to the governing non-linear reaction-diffusion equations will be clarified, and their predictive capabilitieis will be demonstrated. The dynamics of pattern formation will be investigated by comparison with the recent experimental observations made in dry-jet and/or electro-spinning. Recognizing the possible control of domain morphology and improved understanding of mesogenic interactions, the proposed study will be extended to microporous membranes and nano-composites. The theoretical scheme proposed here demonstrates the spation-temporal evolution of the order parameters (such as density, concentration and orientation fluctuations) based on the local free energy and non-local gradient (diffusive) terms. The numerical simulation further illustrates the emergence of the local internal structures during solidification. Moreover, this methodology can applied to elucidating the microfibrillation dynamics in spinning of semicrystalline polymers and hydrogen bonding systems.It is encouraging to discern unique morphological features encompassing (i) nano-tube formation, (ii) concentric rings/spiral-breakup leading to microfibrillation and (iii) viscous fingering patterns. The observed phenomenon of spiral breakup is one of the most debated topics in the no-linear dynamics of excitable media and biological systems. Furthermore, it clearly demonstrates a new approach to the decades-old problem of predicting morphology development in solution-spun fibers such as rough skin/core structures, collapsed kidney shape morphology, and microfibrils. This methodology has potential for modern technological applications including electro-spinning of nano-fibers/tubes, microporous membranes through pattern photopolymerization induced phase separation, and nano-hybrid composites. It is anticipated that these microporous membranes have widespread applications usch as fuel cell membranes, filtration, and drug delivery. Furthermore, some of the simutaion programs have been written in C++ and can be shown on live-mode with the aid of an LCD projector. Such interactive programs are proven to be useful for classroom teaching and demonstration to the public.

本文从实验和理论上阐述了(I)主链液晶聚合物(MCLCP)和/或刚性棒状聚合物溶液固化过程中中空纤维(或纳米管)的形成动力学，(Ii)模式化聚合过程中单体介孔纳米多孔膜的动力学，(Iii)干法喷气纺丝过程中微原纤维的形成动力学，以及(Iv)混杂复合材料。已建立的依赖时间的金兹堡-朗道TDGL(模型C)将与平流项一起用于跟踪溶剂的蒸发和流动。将阐明与控制非线性反应扩散方程有关的所有参数的物理意义，并展示它们的预测能力。花纹形成的动力学将通过与最近在干喷和/或电纺中所做的实验观察相比较来研究。认识到结构域形态的可能控制和对介观相互作用的更好理解，拟议的研究将扩展到微孔膜和纳米复合材料。本文提出的理论方案展示了基于局域自由能和非局域梯度(扩散)项的有序参数(如密度、浓度和取向涨落)的时空演化。数值模拟进一步说明了凝固过程中局部内部组织的出现。此外，这种方法还可以用来解释半结晶聚合物和氢键体系纺丝过程中的微纤颤动力学。这是令人鼓舞的，它包括(I)纳米管的形成，(Ii)导致微纤化的同心环/螺旋断裂和(Iii)粘性指进模式。观察到的螺旋破裂现象是可激发介质和生物系统非线性动力学中最具争议性的话题之一。此外，它清楚地展示了一种新的方法来预测溶液纺丝纤维中几十年来的形态发展问题，例如粗糙的皮肤/核心结构、塌陷的肾脏形状形态和微纤维。这种方法具有潜在的现代技术应用，包括纳米纤维/管的电纺丝，通过模式光聚合诱导相分离的微孔膜，以及纳米混杂复合材料。可以预见，这些微孔膜在燃料电池膜、过滤和药物输送等方面有着广泛的应用。此外，一些仿真程序是用C++编写的，可以在LCD投影仪的帮助下以实时模式显示。这种互动节目被证明对课堂教学和向公众演示很有用。