Constraints in Semicrystalline Polymers During the Transition from the Liquid to the Solid State

技术概述：本课题将研究半晶聚合物从液体到半晶固体转变过程中晶体的限制作用。该研究将回答以下关于结构和弛豫动力学的具体问题。1. 在玻璃化转变处，协同重排区域（crr）的长度（xCRR）是否与固体部分、晶体部分或两者的发展相关？2. α弛豫（玻璃化转变）动力学是否以与这些相同分数的发展相关的方式变化？, 3。凝固过程中形成的纳米相的结构是什么？这些问题的答案将为了解晶体和半结晶聚合物的非晶体部分之间的关系提供一个基本的水平，因为约束发生在从液体到固体的转变过程中。本研究的一个主要和新颖的方面将是使用准等温测量的可逆热容来研究晶体约束形成的时间发展。将分别评估固体部分和结晶部分的时间发展，从结晶的最早阶段，通过球晶撞击，最后完成结晶过程。将使用介电弛豫光谱研究α弛豫（玻璃化转变过程），并使用小角x射线散射和原子力显微镜确定层状结构。非技术概要：塑料是日常生活中无处不在的材料。大多数商业上有用的塑料都是通过加热和加压来加工成所需的形状的。一类重要的塑料包括那些在加工过程中也有结晶能力的塑料。晶体具有非常复杂的形状，并倾向于形成簇状。但在一个非常简单的图片中，晶体就像微型订书钉一样，在纳米尺度上将塑料固定在一起，并防止组成分子四处移动。为了提高塑料的最终性能，重要的是：了解主食何时以及如何形成；描述实际晶体的形状、大小和组织；并确定晶体如何限制其他分子的运动。这项研究将导致塑料的新产品和加工策略，提高我们的全球竞争力。该项目还教育下一代科学家，特别关注聋哑或听力障碍的学生。

TECHNICAL SUMMARY:The confining effect of crystals, during the transformation from liquid to semicrystalline solid of semicrystalline polymers, will be investigated in this research program. The research will answer the following specific questions about structure and relaxation dynamics vis--vis confinement. 1. Does the length, xCRR, of cooperatively rearranging regions, CRRs, at the glass transition correlate with the development of the solid fraction, the crystal fraction, or both? 2. Do the alpha relaxation (glass transition) dynamics vary in a manner correlated with the development of these same fractions? and, 3. What is the structure of the resultant nanophases during solidification? The answers to these questions will provide a fundamental level of understanding about the relationship between the crystals and the non-crystalline portions of the semicrystalline polymer, as confinement occurs during the transition from the liquid to the solid state. A major, and novel, aspect of this research will be the use of quasi-isothermal measurements of the reversing heat capacity to study the time development of formation of the crystal constraints. The time development of the solid fraction, and the crystalline fraction, respectively, will be assessed from the earliest stages of crystallization, through spherulite impingement, and finally to completion of the crystallization process. The alpha relaxation (glass transition process) will be studied using dielectric relaxation spectroscopy, and lamellar structure will be determined using small angle X-ray scattering and atomic force microscopy. NON-TECHNICAL SUMMARY:Plastics are ubiquitous materials in everyday life. The majority of commercially useful plastics are processed using heat and pressure to form them into desired shapes. An important class of plastics comprises those that also have the ability to crystallize during processing. The crystals have very complicated shapes, and tend to form in clusters. But in a very simplified picture, the crystals act like miniature staples, holding the plastic together on the nanometer length scale, and preventing the constituent molecules from shifting around. To improve the ultimate properties of the plastics, it is important to: understand when and how the staples form; characterize the actual crystal shape, size, and organization; and determine how crystals restrict the motion of the other molecules. This research will lead to new products and processing strategies for plastics, improving our global competitiveness. The program also serves to educate the next generation of scientists, with a special focus and outreach to students who are deaf or hard of hearing.