Confined and Directed Polymer Crystallization at Curved Liquid/Liquid Interface

非技术摘要：雪花和钻石等常见晶体有趣的几何形状是由规则的分子堆积决定的。晶体的最小单位，单位细胞，在三维直线上重复自己，生长出这些令人惊叹的物体。但是，如果晶体形成的可用空间是非平坦的，即弯曲的，该怎么办？如何容纳单元格，结构将如何扭曲？当分子填充到晶格中时，它们必须轮换，生成的晶体的形状和性质将发生变化。这个项目关注这样的场景，旨在了解聚合物晶体是如何在非常小的和弯曲的空间中形成的基本原理。等电点最近表明，聚合物在液滴表面结晶可以形成中空晶体胶囊。这些独特的胶囊被称为“结晶体”。在这个项目中，溶液中的结晶将在小液滴中进行。结晶条件和聚合物的分子结构将被系统地改变，以控制结晶体的形状和大小，其结构将使用一些先进的仪器技术来研究。控制良好的晶体小体有望在纳米电机、药物输送和基因治疗等领域得到应用。该提案的教育部分包括：(1)开发将用于高级聚合物表征课程的两个课程单元；(2)指导研究生和本科生；(3)让高中生和教师，特别是来自代表性不足的人群，参与拟议的研究活动；以及(4)参与当地的外联活动，以提高人们对科学和技术的更广泛兴趣。技术综述：结晶本质上是一种普遍存在的自组装过程。根据定义，结晶意味着单位晶胞在平移对称后在三维(3D)晶格中自我重复。另一方面，弯曲的空间本质上与3D平移对称不相称。最近，PI的研究小组在微乳液体系中观察到了一种独特的结晶形态。聚合物结晶被限制在弯曲的液/液界面内，并受其指引。得到了聚合物单晶胶囊，其结构模拟了常见的聚合体。为了描述这种独特的结构，人们创造了“结晶体”一词，这项拟议工作的目标是系统地研究这些特殊的结晶体的结构和结晶行为。该方案的具体目的是为了了解1)微乳液-溶液结晶体系中单晶的生长机理，以及2)这些弯曲晶体中的晶体结构和链堆积。在这个项目中，将使用新型的微乳液溶液结晶方法来制备各种量身定制的晶状体。利用X射线散射、差示扫描量热法、电子显微镜和扫描探针显微镜对这些晶体小体的晶体形态和结构进行了系统的研究。预计该项目将使人们更清楚地了解聚合物在纳米级和弯曲的液/液界面上结晶的机理。

NON-TECHNICAL SUMMARY:The intriguing geometrical shapes of familiar crystals such as snowflakes and diamond are dictated by regular molecular packing. The smallest unit of the crystal, the unit cell, repeats itself in straight lines across three dimensions to grow these stunning objects. But what if the available space for the crystals to form is non-flat, i.e. curved? How could the unit cells be accommodated and how will the structure be distorted? The molecules have to make turns as they pack into the crystalline lattice, and the shape and properties of the resultant crystals will vary. This project is concerned with such a scenario, and aims to understand the fundamentals on how polymer crystals are formed in a very small and curved space. The PI has recently shown that hollow crystal capsules can be formed by crystallizing polymers on the surface of liquid droplets. These unique capsules are termed "crystalsomes". In this project, crystallization from solution will be conducted in small liquid droplets. Crystallization conditions and the molecular structure of the polymers will be systematically varied to control the shape and size of the crystalsomes, whose structure will be studied using a number of advanced instrumental techniques. It is anticipated that well-controlled crystalsomes may find applications in the fields of nanomotors, drug delivery and gene therapeutics. The educational component of the proposal includes: (1) Developing two class modules which will be used in an Advanced Polymer Characterization course; (2) Mentoring graduate and undergraduate students; (3) Involving high school students and teachers, particularly from under-represented populations, in the proposed research activities; and (4) Engaging in local outreach activities to enhance broader interest in science and technology. TECHNICAL SUMMARY: Crystallization is a ubiquitous self-assembly process in nature. By definition, crystallization implies that a unit cell self-repeats in a three-dimensional (3D) lattice following translational symmetry. A curved space, on the other hand, is intrinsically incommensurate with 3D translational symmetry. Recently, the PI's group observed a unique type of crystalline morphology in a miniemulsion system. Polymer crystallization was found to be confined within and directed by the curved liquid/liquid interface. Polymer single crystal-like capsules were obtained and the structure mimics the familiar polymersomes. The term "crystalsome" was coined to describe this unique structure, and the goal of the proposed work is to systematically investigate the structure and crystallization behavior of these peculiar crystalsomes. The specific aims of the proposal are to understand 1) the single-crystal growth mechanism in miniemulsion-solution crystallization systems, and 2) the crystal structure and chain packing in these curved crystalsomes. In this project, a variety of tailor-designed crystalsomes will be fabricated using the novel miniemulsion solution crystallization method. The crystalline morphology and structure of these crystalsomes will be systematically investigated using X-ray scattering, differential scanning calorimetry, electron microscopy, and scanning probe microscopy. It is anticipated that this project will lead to clearer understanding of the mechanism of polymer crystallization at nanosized and curved liquid/liquid interfaces.