Thermodynamics and Dynamics of Mesophases from Novel Self-Assembling Building Blocks

新型自组装砌块的中间相的热力学和动力学

• 批准号: 1033349
• 负责人: Fernando Escobedo
• 金额: $ 25.72万
• 依托单位: Cornell University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-09-01 至 2013-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1033349&HistoricalAwards=false
• 关键词: Thermodynamics; Dynamics; Mesophases; Novel; Self

1033349EscobedoIntellectual Merit:Motivated by the growing ability to experimentally produce particles of almost any imaginable shape in the nano- to micro-size range, the goal of this proposal is to develop and apply novel molecular simulation methods to study the thermodynamic and dynamic properties of partially ordered phases (mesophases) of systems containing rigid colloidal particles of polyhedral shapes. This goal lies within the scope of nanotechnology that seeks to achieve greater control of orderly assembly of nanoscale objects; specifically, by elucidating how multifaceted building blocks form novel self-assembled structures. In this context, particle shape complementarity plays the role of an ?entropic bonding? that helps orient and position particles in regular patterns (even in the absence of chemical selectivity). The particle shapes to be investigated are convex space filling polyhedrons such as polygonal prisms, truncated octahedron, and rhombic dodecahedron.Selected binary mixtures of these particle types will also be studied, including mixtures of triangular and hexagonal prisms (which may template photonic band-gap materials), and mixtures of octahedra and tetrahedra (which would lead to model nano assembled 3D compounds). The models used are coarse grained representations of colloidal particles whose effective inter-particle interactions can be tuned by surface functionalization or by the composition of the solvent media. It is expected that many of these systems will exhibit a liquid crystalline phase or a plastic solid in between the isotropic phase (at low concentrations) and crystal phase (at high concentrations). To identify such mesophases, advanced Monte Carlo methods and order parameters will be used to outline their phase boundaries and characterize their structure. To elucidate how such mesophases form and melt, the kinetics and mechanism of isotropicmesophase transitions will be investigated via novel path sampling methods. To elucidate how particles and defects move in such phases, molecular dynamic simulations will be performed to track and characterize their motion at equilibrium conditions and under steady shear flow. Some of these mesophases may exhibit unusual shear response like flow directionality and yield stress.The methodological developments to be pursued are: (i) optimization of novel forward flux sampling to study the kinetics of order disorder phase transitions and to identify good orderparameters to characterize mechanism, and (ii) extension of expanded ensemble methods to simulate mesophase transitions in pure and binary systems using suitable order parameters. The proposed research can thus be seen as having a dual scope. The primary goal is to elucidate the thermodynamic and dynamic behavior of model rigid building blocks that have potential uses in the nanotechnology of self assembly. The secondary goal is to formulate novel numerical statistical mechanics techniques that have potentially widespread applications.Broader Impacts:This work is complementary to experimental efforts by collaborators who will try to realize the predicted novel phases and test their mechanical, optical, and rheological properties. In the long term, the results could impact the ceramic, plastics, and semiconductor industries by helping broaden the approaches available to develop strong nano composites with high particle loadings, sieves with regular topology, liquid armors, colloid based mesocrystals for light control in photonic materials, sensors and lubricants sensitive to stress directionality, and nanocrystal arrays for photovoltaics. Advances in simulation methods should also help materials modelers to improve product properties by predicting and exploiting meso-scale, entropy aided self-assembly.The graduate and undergraduate students involved with this project will get ample exposure to the physics and engineering of colloids while acquiring a significant expertise on multiple molecular and mesoscopic modeling techniques. They will also coordinate with the Cornell Centerfor Material Research (CCMR) to create a teaching module on Nano-Lego engineering: harnessing entropy to create order? for use in local high schools. Our scientific results will be disseminated through professional meetings and an industrial outreach program organized by CCMR. Results of this investigation will be used in at least two courses: a new course on molecular simulations and the advanced Chemical Engineering thermodynamics core course.

1033349 escobedInclectual功绩：由实验生成纳米尺寸至微型范围中几乎所有可想象形状的颗粒的能力的增长，该提案的目标是开发和应用新颖的分子模拟方法来研究研究的热力学和动力学特性含有多面体形状的刚性胶体颗粒的系统的有序相（中间）。这个目标在于纳米技术的范围，该纳米技术试图更加控制纳米级对象的有序组装；具体而言，通过阐明多方面的构建块如何形成新型的自组装结构。在这种情况下，粒子形状互补性起着？熵键的作用？这有助于定期和定位粒子以常规模式（即使在没有化学选择性的情况下）。待研究的粒子形状是凸出空间填充多面体，例如多边形棱镜，截短的八面体和菱形十二面体。这些粒子类型的二进制混合物也将进行研究，包括三角形和六边形的棱镜的混合物（这可能会模板（可能会模板光子频道浮雕）材料），以及八面体和四面体的混合物（这将导致纳米组装的3D化合物）。所使用的模型是胶体颗粒的粗粒子表示，其有效的颗粒间相互作用可以通过表面功能化或溶剂培养基的组成来调节。预计许多这些系统将在各向同性相（低浓度）和晶相（在高浓度下）之间表现出液晶相或塑性固体。为了识别此类中间相，将使用先进的蒙特卡洛方法和顺序参数来概述其相边界并表征其结构。为了阐明这种中间酶的形成和熔体如何，将通过新型的路径采样方法研究各向同性食管相变的动力学和机制。为了阐明颗粒和缺陷如何在此类阶段移动，将进行分子动态模拟，以跟踪和表征其在平衡条件下和稳定剪切流下的运动。这些中间酶中的一些可能表现出异常的剪切反应，例如流动方向性和产生应力。要追求的方法论发展是：（i）优化新型的前向通量采样以研究有序障碍相变的动力学，并确定良好的订单参数以识别机制以表征机制，和（ii）扩展扩展的集合方法，以使用合适的订单参数模拟纯和二进制系统中的中间机过渡。因此，提出的研究可以看作是具有双重范围。主要目标是阐明在自组装的纳米技术中具有潜在用途的模型刚性构件的热力学和动态行为。第二个目标是制定具有潜在广泛应用的新型数值统计力学技术。Boader的影响：这项工作与合作者的实验努力相辅相成，他们将试图实现预测的新阶段并测试其机械，光学和流变学特性。从长远来看，结果可能会通过帮助扩大具有高颗粒负荷的强纳米复合材料的方法来影响陶瓷，塑料和半导体行业，对应力方向性敏感的传感器和润滑剂，以及对光伏的纳米晶体阵列。模拟方法的进步还应通过预测和利用中级，熵辅助自组装来帮助材料建模者提高产品性能。与该项目有关的研究生和本科生将获得充分的胶体物理和工程的影响，同时获得胶体的物理和工程多重分子和介绍建模技术的重要专业知识。他们还将与康奈尔中心（Cornell Center）进行材料研究（CCMR）协调，以创建一个关于纳米级工程学的教学模块：利用熵来创建订单？用于当地高中。我们的科学结果将通过专业会议和CCMR组织的工业外展计划进行传播。该研究的结果将在至少两个课程中使用：分子模拟的新课程和高级化学工程热力学核心课程。