Collaborative Research: Synthesis and Theology of Strategically-Designed Long-Chain-Branched Polymers

合作研究：战略设计的长链支化聚合物的合成和流变学

• 批准号: 0906893
• 负责人: Jimmy Mays
• 金额: $ 16万
• 依托单位: University of Tennessee Knoxville
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-09-01 至 2013-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0906893&HistoricalAwards=false
• 关键词: Collaborative; Research; Synthesis; Theology; Strategically

TECHNICAL SUMMARY Understanding remains incomplete regarding the relaxation of complex branching structures in entangled polymer melts with multiple branch points, such as H- or comb-branched polymers, or for polymers with branches of differing lengths, such as asymmetric stars and asymmetric H polymers, or for hyperbranched polymers (i.e., with branch-on-branch topology). To address these issues, which are important both scientifically and for applications to commercial polymer manufacture, we are performing a combination of the following tasks: 1. Synthesis of high-quality model branched polymers with branches of the same or different length that are carefully designed to test physical theories. 2. Careful characterization of the molecular weight and branching properties of these polymers. 3. Measurement of the linear rheological properties over a wide frequency range. 4. Comparison of the measured viscoelastic properties with predictions derived from the various alternative proposed theories. We plan to accomplish these tasks through a collaborative framework, involving a collaborator, Jimmy Mays, who will use a novel route to synthesize 1) asymmetric H polymers; 2) asymmetric star-on-star polymers, based on a core star polymer, each branch of which terminates in two unequal length branches; and 3) combs with tetrafunctional branch points. These polymers will be carefully characterized by gel permeation chromatography and TGIC, and studied through rheological measurements, including careful long-time creep rheometry with the help of instrumentations and methods available in the laboratory of Prof. John Dealy, a collaborator at McGill University. Existing computational models for predicting the measured rheology will be employed in collaboration with Chinmay Das in the McLeish group at Leeds University. NON-TECHNICAL SUMMARY:To form advanced plastic fibers or thin plastic sheets used for packaging, molten plastic is pulled or stretched at extremely high speeds. The performance of this process depends on how the polymer molecules in the plastic are entangled with each other, and how they escape those entanglements. Polymers that branch into multiple long strands are exceptionally useful for industry, since they serve as netting that strengthens the plastic so that it does not rip or bursting when blown into shape. Larson?s team has found that changes to as few one branch in a million branch points can significantly impact the properties of the melt relevant to its strength as a melt. The reason for this is that branched polymers entangle extremely well with other branched polymers. To escape these entanglements, they must reconfigure by reeling branches towards the branch point, like Houdini dislocating his shoulder to escape a straight jacket. Therefore, the entanglements are long-lived and make the plastic easier to shape. Larson?s team is chemically synthesizing special branched polymers that are exceptionally useful in determining how branched polymers manage to perform their ?Houdini? acts and how to optimize this for advanced performance. Their measurements of the rates at which polymers escape entanglements is providing knowledge that is of great interest to collaborators at Dow Chemical Company and other plastics manufacturing companies. The research has been highly interdisciplinary and international with collaborators at the University of Tennessee, McGill University, the University of Leeds, and Dow Chemical Company.

技术概要 对于具有多个支化点的缠结聚合物熔体中复杂支化结构的弛豫，如 H 或梳状支化聚合物，或具有不同长度支链的聚合物，如不对称星形和不对称 H 聚合物，或超支化聚合物（即具有支链拓扑结构），了解仍然不完整。 为了解决这些对科学和商业聚合物制造应用都很重要的问题，我们正在执行以下任务的组合： 1. 合成具有相同或不同长度支链的高质量模型支化聚合物，这些聚合物经过精心设计以测试物理理论。 2. 仔细表征这些聚合物的分子量和支化特性。 3. 在宽频率范围内测量线性流变特性。 4. 将测量的粘弹性特性与从各种替代理论得出的预测进行比较。 我们计划通过一个协作框架来完成这些任务，其中包括合作者吉米·梅斯（Jimmy Mays），他将使用一种新颖的路线来合成 1）不对称 H 聚合物； 2)不对称星对星聚合物，基于核心星形聚合物，其每个分支以两个不等长的分支终止； 3)具有四官能分支点的梳。这些聚合物将通过凝胶渗透色谱和 TGIC 进行仔细表征，并通过流变测量进行研究，包括借助麦吉尔大学合作者 John Dealy 教授实验室提供的仪器和方法进行仔细的长时间蠕变流变测量。 将与利兹大学 McLeish 小组的 Chinmay Das 合作使用现有的计算模型来预测测量的流变学。非技术摘要：为了形成用于包装的高级塑料纤维或薄塑料片，熔融塑料以极高的速度被拉动或拉伸。该过程的性能取决于塑料中的聚合物分子如何相互缠结，以及它们如何摆脱这些缠结。分支成多条长链的聚合物在工业上特别有用，因为它们可以充当增强塑料的网，使其在吹塑成型时不会撕裂或破裂。拉尔森的团队发现，一百万个分支点中哪怕只有一个分支的变化都会显着影响与熔体强度相关的熔体特性。其原因是支化聚合物与其他支化聚合物缠结得非常好。为了摆脱这些纠缠，他们必须通过将树枝卷向分支点来重新配置，就像胡迪尼脱臼肩膀以逃脱直筒夹克一样。因此，缠结的寿命很长，并且使塑料更容易成型。拉尔森的团队正在化学合成特殊的支化聚合物，这种聚合物对于确定支化聚合物如何设法发挥其“Houdini”功能非常有用。行为以及如何优化它以获得先进的性能。 他们对聚合物脱离缠结的速率的测量为陶氏化学公司和其他塑料制造公司的合作者提供了非常感兴趣的知识。该研究具有高度跨学科性和国际性，合作者来自田纳西大学、麦吉尔大学、利兹大学和陶氏化学公司。