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.

本提案需要实验和理论阐明（i）主链液晶聚合物（MCLCP）和/或刚性棒聚合物溶液固化过程中中空纤维（或纳米管）形成的动力学，（ii）图案聚合过程中单体介晶纳米多孔膜的动力学，（iii）干喷射过程中微纤维形成的动力学 纺纱，以及（iv）混合复合材料。 完善的时间相关的 Ginzburg-Landau TDGL（模型 C）将与平流项结合应用，用于跟踪溶剂蒸发和流动。 与控制非线性反应扩散方程有关的所有参数的物理意义将被阐明，并且它们的预测能力将被证明。 将通过与最近在干喷射和/或静电纺丝中进行的实验观察进行比较来研究图案形成的动力学。 认识到域形态的可能控制和对介晶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。 这里提出的理论方案展示了基于局部自由能和非局部梯度（扩散）项的有序参数（例如密度、浓度和方向涨落）的时空演化。 数值模拟进一步说明了凝固过程中局部内部结构的出现。 此外，这种方法可以应用于阐明半结晶聚合物和氢键系统纺丝中的微纤化动力学。令人鼓舞的是辨别独特的形态特征，包括（i）纳米管形成，（ii）导致微纤化的同心环/螺旋破裂和（iii）粘性指状模式。 观察到的螺旋破裂现象是可兴奋介质和生物系统的非线性动力学中最具争议的话题之一。 此外，它清楚地展示了一种新方法，可以解决数十年来预测溶液纺丝纤维形态发展的问题，例如粗糙的皮/芯结构、塌陷的肾形形态和微纤维。 该方法具有现代技术应用的潜力，包括纳米纤维/管的静电纺丝、通过图案光聚合诱导相分离的微孔膜以及纳米混合复合材料。 预计这些微孔膜具有广泛的应用，如燃料电池膜、过滤和药物输送。 此外，一些模拟程序是用 C++ 编写的，可以借助 LCD 投影仪以实时模式显示。 事实证明，此类互动程序对于课堂教学和向公众演示非常有用。