FRG: GOALI: Collaborative Research: The Role of Polymer Molecular Architecture in Controlling Morphology in Quiescent and Flow-Induced Crystallization

技术总结这项提议将弗吉尼亚大学、康奈尔大学和佛罗里达州立大学的学术研究小组与埃克森美孚研究和工程公司的一位领先的聚烯烃工业科学家联合起来。这项研究的重点是开发新型的聚丙烯合成化学，探索半结晶聚合物在静态和流动诱导结晶中成核和生长的基本物理现象。具体地说，PI将使用支化结构作为控制成核的工具，从而控制最终的结晶形态和宏观材料性能。为实现这一目标而组建的团队擅长于新型聚烯烃的合成、结晶动力学和结构表征、流变学和流动诱导结晶，以及工业聚合物加工。模型等规聚丙烯(IPP)材料，包括窄分子量分布的线形、星形、H-和梳形聚合物，将被精确地控制立体规整性和支化点的位置。静态结晶实验将主要试图确定：(1)支化引起的链不规律性增加对均聚物样品中α相和伽马相的结晶组织水平和相对含量的影响；(2)支化结构的类型和构象增强线性链共混物的成核。流动诱导共混物的流动诱导结晶将试图确定：(1)支化固定最长驰豫时间对结晶动力学、成核密度、结晶度和晶体结构的影响；(2)分子结构是否改变局部链段取向以促进成核；以及(3)多态和形态如何依赖于臂的数量(星)、支链与主链的分子量比(H-聚合物)和支点的数量(梳子)。非技术性SUMMARYO美国每年生产超过4300万吨热塑性树脂，估计市场价值超过650亿美元。许多处理是以特别的方式执行的，没有建模或连贯的混合策略的好处。由于原材料往往是不可再生的，加工过程中的废物对环境有重大影响。此外，更好地控制结晶度和结晶形态的能力将导致更好的薄膜、更轻的部件，并由于材料性能的扩展而将廉价的PP材料注入到新的应用中。通过提供定义明确的材料体系的静态和流动诱导结晶数据，这项工作有望产生能够定量预测半结晶形态的理论工具。化学和化学工程专业的学生不仅将接触到现代聚合物合成和表征、流变学和材料表征技术(例如X射线散射、双折射、光学和透射电子显微镜)，还将能够参与埃克森美孚的工业研究经验。PIs还将结合他们不同的才华和观点来组织一个关于“塑料”的K12教育计划，并在他们各自的社区中采用。私人投资机构也有将代表性不足的群体纳入其研究工作的记录(例如，来自加纳和巴拿马的本科生以及几名女本科生、毕业生和博士后)。此外，FAMU-FSU工程学院是由FAMU和FSU共同管理的项目，FAMU是一所历史上的黑人学院和大学，FSU有40%的少数民族和25%的女性入学，许多非裔美国本科生在该机构的PI实验室进行本科生研究。

TECHNICAL SUMMARYThis proposal unites academic research groups at the University of Virginia, Cornell University, and Florida State University with a leading polyolefin industrial scientist at ExxonMobil Research and Engineering Corporation. The research focuses on the development of novel polypropylene synthetic chemistry and an exploration of the fundamental physical phenomena underlying nucleation and growth in quiescent and flow-induced crystallization of semicrystalline polymers. Specifically, the PIs will use branching architecture as a tool to control nucleation and thereby manipulate the final crystalline morphology and macroscopic material properties.The team assembled to achieve this goal is skilled in novel polyolefin synthesis, crystallization kinetics and structural characterization, rheology and flow-induced crystallization, and industrial polymer processing. Model isotactic polypropylene (iPP) materials, including narrow molecular weight distribution linear, star, H-, and comb polymers, will be synthesized with precisely controlled stereoregularity and location of branch points. Quiescent crystallization experiments will principally seek to ascertain: (1) the influence of increasing chain irregularity due to branching on the level of crystalline organization and relative content of the alpha and gamma phases in homopolymer samples; and (2) the type and conformation of branching architecture that enhances nucleation in blends with linear chains.Flow-induced crystallization of linear and branched iPP blends will seek to determine: (1) how crystallization kinetics, nucleation density, degree of crystallinity, and crystalline structure are influenced by branching for fixed longest relaxation time; (2) if molecular architecture alters the local segmental orientation to promote nucleation; and (3) how polymorphism and morphology depend upon the number of arms (stars), ratio of branch to main chain molecular weight (H-polymers), and number of branch points (combs). NON-TECHNICAL SUMMARYOver 43 million tons of thermoplastic resins are produced in the U.S. each year with an estimated market value of over $65 billion. Much processing is performed in an ad hoc manner without the benefit of modeling or coherent blending strategies. Since the raw materials are often not renewable, waste in processing has a significant environmental impact. Moreover, the ability to exert better control over crystallinity and crystalline morphology will lead to better films, lighter weight parts, and also inject inexpensive PP materials into novel applications due to extended material properties. By providing quiescent and flow-induced crystallization data on well-defined material systems, theoretical tools allowing quantitative predictions of semicrystalline morphology are expected to result from this work. Students in Chemistry and Chemical Engineering will be not only be exposed to modern polymer synthesis and characterization, rheology, and material characterization techniques (e.g., X-ray scattering, birefringence, optical and transmission electron microscopy), but they will also be able to participate in industrial research experiences at ExxonMobil. The PIs will also combine their diverse talents and perspectives to assemble a K12 educational program on "Plastics" to be adopted in their respective communities. The PIs also have a record of including underrepresented groups in their research efforts (e.g., undergraduates from Ghana and Panama and several female undergraduates, graduates, and postdocs). Additionally, the FAMU-FSU College of Engineering is a jointly managed program of FAMU, a historically black college and university, and FSU with 40% minority and 25% female enrollment, and numerous African-American undergraduates have conducted undergraduate research in the laboratory of the PI at that institution.