Supramolecular Assembly of Charged Nanoparticles: Understanding the Nucleation Process that Connects Kinetic and Equilibrium Behaviors

纳米粒子的许多技术应用依赖于我们控制纳米粒子相互作用的能力，以利用它们的有序结构和集体性质。在这个由化学系大分子、超分子和纳米化学项目资助的项目中，康涅狄格大学的姚林教授和他的学生正在进行研究，以了解使纳米颗粒与不同类型的分子（配体）接枝在溶液中的可控组装成为可能的物理机制，并预测进一步聚集和分散的趋势在哪里平衡，从而达到平衡。一个目标是预测和控制从大量纳米粒子形成更大的“超分子”结构的一般方法。了解组装过程的机制有助于生成分层的多组分材料和系统，最终接近自然界中发现的复杂程度。利用生物启发机制合成超分子结构为化学研究和教育提供了新的机遇和挑战。PI旨在满足学生在这一新兴领域的跨学科教育和高质量研究经验的需求。拟议的研究将纳入课程材料和外联活动，为不同层次的学生提供跨学科培训和充满活力的研究经验。分子间的相互作用决定了大规模超分子结构形成的自组装途径和动力学。在自然界中，许多球状蛋白质可以通过明确的成核生长机制“聚合”成特定的螺旋或管状组件，如肌动蛋白丝和微管的形成。受复杂组装机制的启发，PI正在开发一种用于配体接枝的带电纳米颗粒的受控组装的通用策略。在热力学分析的指导下，在初步研究中成功地创建了由多肽接枝的带电纳米颗粒组装的纤维状超分子结构。以这些纳米粒子为模型体系，研究重点是：（1）进行动力学分析，以了解带电纳米粒子的纤维状超分子组装中涉及的成核机制;（2）确定带电纳米粒子自缔合的相图，并阐明不同超分子结构之间的转变机制。通过模仿自然界的组装方法，该研究正在开发一种将纳米颗粒构建块组装到可预测的超结构的通用策略，并提供对连接纳米颗粒自缔合的动力学和平衡行为的关键成核过程的见解。特别是，热力学和动力学过程中所涉及的纳米粒子的纤维组装测试的适用性从蛋白质聚合的研究中获得的经典理论的理解，导致需要开发一个更广义的模型。

Many technological applications of nanoparticles rely on our ability to control the interactions of nanoparticles to exploit their ordered structures and collective properties. In this project funded by the Macromolecular, Supramolecular and Nanochemistry Program of the Chemistry Division, Prof. Yao Lin and his students at University of Connecticut are conducting studies to understand the physical mechanisms that make possible the controlled assembly in solution of nanoparticles with different types of molecules (ligands) grafted onto them, and to predict where the tendencies to aggregate further and to disperse are balanced so that equilibrium is reached. A goal is a general approach for prediction and control of the formation of bigger "supramolecular" structures from a large set of nanoparticles. Understanding the mechanism of the assembly process can contribute to the generation of hierarchical, multicomponent materials and systems, eventually approaching the level of sophistication found in nature. Using biologically inspired mechanisms to synthesize supramolecular structures provides new opportunities and challenges in chemical research and education. The PI aims to address students needs for interdisciplinary education and high quality research experience in this emerging field. The proposed research will be integrated into curriculum materials and outreach activities, providing interdisciplinary training and vibrant research experiences for students at different levels. Intermolecular interactions define the self-assembly pathways and the kinetics of the formation of large-scale supramolecular structures. In nature, numerous globular proteins can be "polymerized" into specific helical or tubular assemblies via a well-defined nucleation-growth mechanism, as exemplified by the formation of actin filaments and microtubules. Inspired by the sophisticated assembly mechanism, the PI is developing a general strategy for controlled assembly of ligand-grafted, charged nanoparticles. Guided by a thermodynamic analysis, fibrous supramolecular structures assembled from polypeptide-grafted, charged nanoparticles have been successfully created in the preliminary study. Using these nanoparticles as a model system, the research focuses on: (1) conducting kinetic analysis to understand the nucleation mechanism involved in the fibrous supramolecular assembly of charged nanoparticles, and (2) determining the phase diagram for the self-association of charged nanoparticles and elucidating the transition mechanism between different supramolecular structures. By mimicking nature's assembly approaches, the research is developing a general strategy for assembling nanoparticle building blocks to predictable superstructures, and providing insights into the critical nucleation process that connects kinetic and equilibrium behaviors of nanoparticles self-associations. Particularly, the understanding of thermodynamic and kinetic processes involved in the fibrous assembly of nanoparticles tests the applicability of classic theories obtained from the studies of the protein polymerizations, leading to the need for development of a more generalized model.