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

技术摘要本提案将弗吉尼亚大学、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与工程公司的一位领先的聚烯烃工业科学家联合起来。 该研究的重点是开发新型聚丙烯合成化学和探索基本的物理现象，潜在的成核和生长在静态和流动诱导结晶的半结晶聚合物。 具体而言，PI将使用支化结构作为控制成核的工具，从而操纵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精通新型聚烯烃合成、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。 等规聚丙烯（iPP）模型材料，包括窄分子量分布的线型、星星型、H型和梳型聚合物，将通过精确控制立构规整性和分支点位置来合成。 静态结晶实验将主要寻求确定：（1）由于支化而增加的链不规则性对均聚物样品中结晶组织水平和α和γ相的相对含量的影响;以及（2）在具有直链的共混物中增强成核的支化结构的类型和构象。直链和支化iPP共混物的流动诱导结晶将寻求确定：（1）对于固定的最长弛豫时间，支化如何影响结晶动力学、成核密度、结晶度和晶体结构;（2）分子结构是否改变局部链段取向以促进成核;以及（3）多晶型和形态如何依赖于臂（星形）的数目、分支与主链分子量的比率（H-聚合物）和分支点（梳）的数目。 非技术总结美国每年生产超过4300万吨热塑性树脂，估计市场价值超过650亿美元。 许多处理都是以特别的方式进行的，没有建模或连贯的混合策略的好处。 由于原材料通常不可再生，加工过程中产生的废物对环境有重大影响。 此外，对结晶度和结晶形态施加更好控制的能力将导致更好的膜、更轻的重量部件，并且由于扩展的材料特性，还将廉价的PP材料注入到新的应用中。 通过提供静态和流动诱导结晶数据定义明确的材料系统，理论工具，允许定量预测半结晶形态，预计将导致这项工作。 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），但他们也将能够参与埃克森美孚的工业研究经验。 PI还将联合收割机结合他们的不同人才和观点，组装一个K12教育计划的“塑料”将在各自的社区采用。 PI也有在其研究工作中包括代表性不足的群体的记录（例如，来自加纳和巴拿马的本科生以及几名女本科生、研究生和博士后）。 此外，FAMU-FSU工程学院是FAMU的联合管理计划，FAMU是一所历史悠久的黑人学院和大学，FSU拥有40%的少数民族和25%的女性入学率，许多非洲裔美国本科生在该机构的PI实验室进行了本科生研究。

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.