Confined and Directed Polymer Crystallization at Curved Liquid/Liquid Interface

非技术概要：我们熟悉的晶体，如雪花和钻石，其迷人的几何形状是由规则的分子排列决定的。晶体的最小单位，单位细胞，在三维空间中以直线重复自身，从而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，即弯曲的呢？如何容纳单元格，结构将如何扭曲？当分子进入晶格时，它们必须进行旋转，形成的晶体的形状和性质也会发生变化。这个项目关注的是这样一个场景，旨在了解聚合物晶体如何在一个非常小的弯曲空间中形成的基本原理。PI最近表明，通过在液滴表面结晶聚合物可以形成空心晶体胶囊。这些独特的胶囊被称为“晶体体”。在这个项目中，溶液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，以控制晶体体的形状和大小，其结构将使用一些先进的仪器技术进行研究。可以预见，控制良好的晶体体在纳米运动、药物传递和基因治疗等领域可能会有应用。该提案的教育部分包括：(1)开发两个课程模块，将用于高级聚合物表征课程；(2)指导研究生和本科生；(3)让高中学生和教师，特别是来自代表性不足人口的学生和教师参与拟议的研究活动；（四）在本地开展外展活动，提高公众对科技的兴趣。技术概述：结晶是自然界中普遍存在的自组装过程。根据定义，结晶意味着一个单位细胞在三维（3D）晶格中遵循平移对称自我重复。另一方面，弯曲空间本质上与三维平移对称不相称。最近，PI的研究小组在微乳液体系中观察到一种独特的晶体形态。聚合物的结晶被限制在弯曲的液/液界面内并受其支配。获得了聚合物单晶状胶囊，其结构与常见的聚合体相似。术语“晶体体”是用来描述这种独特的结构，而提出的工作的目标是系统地研究这些特殊晶体体的结构和结晶行为。本研究的具体目的是了解1)微乳-溶液结晶体系中单晶的生长机制，以及2)这些弯曲结晶体的晶体结构和链式排列。在本项目中，将使用新型的微乳液溶液结晶方法制备各种量身定制的晶体体。这些晶体体的晶体形态和结构将使用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进行系统的研究。预计该项目将有助于更清楚地了解聚合物在纳米级和弯曲的液/液界面上的结晶机理。

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.