Kinetic Control of Crystalline Order in Olefin-Based Polymers

烯烃基聚合物晶序的动力学控制

• 批准号: 1105129
• 负责人: Rufina Alamo
• 金额: $ 46万
• 依托单位: Florida State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-06-01 至 2016-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1105129&HistoricalAwards=false
• 关键词: Kinetic; Control; Crystalline; Order; Olefin

TECHNICAL SUMMARYResearch is proposed to advance knowledge of the interplay between chain microstructure, phase structure, crystallization kinetics and morphology of non-oriented bulk crystallized polyolefins. The aim is to understand this interplay using well-characterized systems that serve as models to predict the behavior of more complex commercial systems. Molecules could then be tailored with unique crystalline morphologies and properties. We seek to understand from first principles the role of crystallization kinetics on the development of the ultimate crystalline state. Of interest is the effect of undercooling on nucleus size, nature of folding when enabled, and impact in packing of sequence-specific macromolecules. Using polyethylene-based molecules with exquisite control in halogen substitution as model systems to predict kinetically controlled polymorphic transitions, further insights into primary chain deposition and subsequent arrangements are sought as they relate to classical and novel views of the path to polymer crystallization. In blends of metallocene-made poly(propylene) and higher alpha-olefin random copolymers, the role of sequence length distribution in polymorphic behavior and the crystalline phase structure that evolves will be addressed for a wide range of compositions.NON- TECHNICAL SUMMARYThe main proposed work involves the two leading commercial polyolefins, polyethylenes and polypropylenes. As they comprise over half of the annual production of all synthetic polymers, any improvement in the product, either by branching architecture, rate of processing, or judicious component blending will lead to a significant impact in the US and world economy. Most properties of these polyolefins are directed by the fraction and type of crystalline order that they assemble, which is a function of branching content and distribution. Commercial polyolefins are too complex in chain length and branching distributions to generate fundamental relations between chain-structure and properties. In the work proposed, polyethylenes and polypropylenes synthesized with exquisite control of branching distribution, either at a precise regular spacing or randomly placed will be studied as models to establish fundamental behaviors. Special emphasis is given to the role of crystallization kinetics, as it relates to processing rate, in the type of crystals assembled. Crystals with different degrees of symmetry are predicted with the model systems, thus bringing the opportunity to develop new polyolefins in which polymer primary structure can be manipulated to control physical properties. This fundamental research is also aimed to provide learning opportunities for both graduate and undergraduate students, many of them minority.

技术概要提出的研究旨在增进对非取向本体结晶聚烯烃的链微观结构、相结构、结晶动力学和形态之间相互作用的认识。目的是使用特征良好的系统来理解这种相互作用，这些系统作为模型来预测更复杂的商业系统的行为。然后可以定制具有独特晶体形态和特性的分子。我们试图从第一原理出发理解结晶动力学对最终晶态发展的作用。令人感兴趣的是过冷对核大小的影响、启用时折叠的性质以及对序列特异性大分子堆积的影响。使用对卤素取代具有精确控制的聚乙烯基分子作为模型系统来预测动力学控制的多晶型转变，寻求对主链沉积和后续排列的进一步了解，因为它们与聚合物结晶路径的经典和新颖观点相关。在茂金属制造的聚（丙烯）和高级α-烯烃无规共聚物的共混物中，序列长度分布在多晶型行为和演化的结晶相结构中的作用将针对多种组合物得到解决。非技术概要主要提出的工作涉及两种领先的商业聚烯烃：聚乙烯和聚丙烯。由于它们占所有合成聚合物年产量的一半以上，因此产品的任何改进，无论是通过支化结构、加工速率还是明智的成分混合，都将对美国和世界经济产生重大影响。这些聚烯烃的大多数性能取决于它们组装的晶序的分数和类型，这是支化含量和分布的函数。 商业聚烯烃的链长和支化分布过于复杂，无法在链结构和性能之间产生基本关系。 在所提出的工作中，通过精确控制支化分布（无论是以精确的规则间距还是随机放置）合成的聚乙烯和聚丙烯将作为模型进行研究，以建立基本行为。特别强调结晶动力学的作用，因为它与组装晶体类型中的加工速率有关。通过模型系统预测具有不同对称度的晶体，从而为开发新的聚烯烃提供了机会，其中可以操纵聚合物的一级结构来控制物理性能。这项基础研究还旨在为研究生和本科生（其中许多是少数民族）提供学习机会。