Self-Assembly and Crystallization in Nanoscale Confinement

概述/摘要分子组装和结晶的尺寸效应已经成为包括制药和保健产品、食品和营养材料、石油化工和有机精细化学品在内的广泛工业领域的关键问题。例如，已知药物胶囊会影响药物的固态形式，从而影响其循环半衰期和生物利用度。薄膜微电子器件的表面图形和缺陷接近临界晶核尺寸，必然会影响薄膜微电子器件的结晶度和电荷输运特性。 随着高通量结晶筛选中的集成流体模式变得越来越小和复杂，理解纳米级的流体通道几何形状和尺寸如何影响成核和结晶过程至关重要。在这些技术实现之前，必须解决纳米限制效应，本项目主要研究当限制尺寸接近临界尺寸时，有机分子在图案上和结构介质中的结晶行为。中心假设是：1）当限制尺寸大于临界核直径时，将发生特定位置的结晶，其形状、尺寸和分布由图案决定; 2）当限制尺寸小于临界尺寸时，图案将阻止成核或捕获预临界团簇。研究将开始与简单的亲脂性苯甲酸作为成核剂和脂质/烷烃双层作为限制介质。封装研究将与马克斯普朗克胶体和界面研究所合作，使用具有化学异质性的逐层（LbL）胶囊模拟脂质双层。将使用原子力显微镜、共焦拉曼显微光谱和选区电子衍射进行结构分析。该研究的目的是：1）监测成核和结晶的早期阶段，2）在临界尺寸处使用限制来控制晶体形态。限制结晶步骤的实验研究是必要的，以更好地了解离散分子簇途中经历的临界核和最终的晶体结构的结构和形态转变。自组装图案化方法使得能够研究组成分子结构与图案结构之间的关系。分子光滑的图案允许一个单独的研究所施加的化学异质性，而不是由topography.The项目解决了基本上悬而未决的问题的稳定性和秩序的前临界集群，尽管最近的证据表明，这种集群可以存在于nanofinition，甚至可能是高度有序的。这种方法与已建立的方法的另一个重要的概念偏差是实现特定位置的成核和定向晶体生长，即，方位角结晶，通过纳米粒子。外延结晶需要客体/主体晶面的尺寸和立体化学匹配。该项目旨在表明，方位角结晶可以实现没有这种严格的限制，并没有事先知道的客体晶体结构。1)技术.分子组装体的限制适用于药物封装、分子电子电路和高通量结晶筛选。2)国际合作的博士学生将受益于在胶体和表面科学的领先国际研究机构工作。3)研究与教育的融合。PI正在努力更新韦恩州基础材料工程课程，并为化学工程B创建纳米技术轨道。

SUMMARY / ABSTRACTThe size effect on molecular assembly and crystallization has emerged as a critical issue in a wide range of industrial sectors including pharmaceutical and healthcare products, food and nutritional materials, petrochemicals, and organic fine chemicals. For example, drug capsules are known to affect a drugs solid-state form and therefore its circulating half-life and bioavailability. Surface patterns and defects approaching the critical nucleus size will certainly influence the crystallinity and charge transport properties of thin film microelectronic devices. As the integrated fluidic patterns in high-throughput crystallization screening become increasingly small and sophisticated, it is essential to understand how fluid channel geometry and size at nanoscale affect the nucleation and crystallization processes. The nanoconfinement effect must be addressed before these technologies can come to fruition.This project focuses on the crystallization behavior of organic molecules onpatterns and in structured media when the confinement size is near the critical dimension. Thecentral hypotheses are 1) when the confinement size is greater than the critical nucleus diameter, site-specific crystallization will occur whose shape, size, and distribution are dictated by the pattern; and 2) when the confinement size is less than the critical size, the pattern will either prohibit nucleation or trap precritical clusters. The research will begin with simple lipophilic benzoic acids as the nucleating agents and lipid/alkane bilayers as the confining media. Encapsulation studies will be conducted in collaboration with the Max Planck Institute of Colloids and Interfaces using layer-by-layer (LbL) capsules with chemical heterogeneity mimicking the lipid bilayer. Structural analysis will be conducted using Atomic Force Microscopy, Confocal Raman Microspectroscopy, and Selected Area Electron Diffraction. The aims of the research are 1) to monitor nucleation and early stages of crystallization, and 2) to control crystal morphology using confinement at the critical dimension.INTELLECTUAL MERIT. Experimental studies of crystallization steps in confinement are necessary for a better understanding of structural and morphological transitions undergone by discrete molecular clusters en route to the critical nucleus and the final crystal structure. The self assembled patterning method enables the investigation of the relationship between the consitituent molecular structure and the pattern structure. The molecularly smooth pattern allows a separate study of confinement imposed by chemical heterogeneity rather than by topography.The project addresses the largely unresolved issue concerning the stability and order of the precritical clusters despite recent evidence that such clusters can exist in nanoconfinement and may even be highly ordered. The other significant conceptual deviation of this approach from the established ones is to achieve site-specific nucleation and oriented crystal growth, i.e., azimuthal crystallization, by nanopatterns. Epitaxy crystallization requires the dimensional and stereochemical match of the guest/host crystalline planes. The project intends to show that azimuthal crystallization can be achieved without such stringent constraints and with no prior knowledge ofthe guest crystal structure.BROAD IMPACTS. 1) Technology. Confinement of molecular assemblies is applicable to drug encapsulation, molecular electronic circuitry, and high-throughput crystallization screening. 2) International cooperation. The Ph.D. students will benefit from working at a leading international research institution in colloids and surface science. 3) Integration of research and education. The PI is leading the efforts to update Wayne States Basic Materials Engineering curriculum and to create a Nanotechnology Track for a Chemical Engineering B.Sc. degree.