Polyolefin Miscibility: New Insights from an Experimental Molecular Perspective

聚烯烃混溶性：实验分子视角的新见解

• 批准号: 0512218
• 负责人: Jeff White
• 金额: --
• 依托单位: North Carolina State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-08-01 至 2006-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0512218&HistoricalAwards=false
• 关键词: Polyolefin; Miscibility; New; Insights; Experimental

Polyolefins comprise an economically and technologically important class of materials.As a subset of all polymers, they are in general well-known, but continuing improvements inmetallocene polymerization catalysis have demonstrated that enhanced physical properties areaccessible through copolymerization, blending, and composites. Consequently, polyolefins andtheir blends span the gamut of possible applications, ranging from low-cost disposable foodpackaging to multicomponent composites for aerospace structural design. In all cases involving more than just a pure polymer, which is the majority, the morphology and local structure of the blend or composite determines the final physical and performance properties of the material.Surprisingly, first-principle mixing rules for polyolefin blends are not known, as thesechemically simple polymers defy like dissolves like solubility conventions. Intellectual Merit. A conspicuous lack of experimental data at the molecular or chain levelsuggests that chain-structure/miscibility relationships in bulk polyolefin mixtures are far frombeing realized. The microscopic to mesoscopic (i.e. angstroms to tens of nanometers) lengthscales accessible by solids NMR experiments can address this deficiency in a non-invasivemanner. Through acquisition of the chain-specific data (dynamics and distance) needed toresolve long-standing questions about the relative importance of chain packing and chainarchitecture, the role of each in determining entropic versus enthalpic contributions to the overallphase behavior may be examined. Broader Impact. The fundamental scientific questions surrounding polyolefin phase behavior,particularly for amorphous polyolefins in the melt or solid states, are far reaching in thatmixtures of these nonpolar, noncrystalline polymers constitute a limiting class ofmacromolecular thermodynamics. As such, polyolefins and their blends are ideal systems for theexperimental study of some long-standing questions in polymer science. For example, bulkamorphous polyolefins are concentrated systems, with many degrees of freedom. Given thevarying chain architectures possible with polyolefins, can distinct degrees of freedom within andbetween molecules (rational introduction of dynamic heterogeneity fluctuations) be identifiedand related to phase behavior/phase transitions? The length-scale and time-scale of phasetransitions in amorphous macromolecules, like those in liquid crystals, have been described inthe context of configurational entropy arguments. Can we, using bulk polyolefins and theirblends, provide non-invasive experimental confirmation of this view at the local chain level (1-10 nm)? If glass formation in non-interacting molecules is driven by loss of configurationalentropy, can molecular level (less than the polymer radius of gyration) experiments detect anddefine local Tg's? Can this data be used to help broaden the scope of current thermodynamicmodels of polymer phase behavior to include configurational entropy contributions? The PI has been, and will continue to be, an active participant at all levels of educationthrough this project. The PI, whose efforts are leveraged through the public outreach director inthe NCSU chemistry department, has presented multiple demonstrations in physical science, andpolymer science, at elementary, middle, and high school venues. Moreover, themultidisciplinary aspect of this project (spectroscopy, polymer chemistry, polymer physics,materials science) continues to attract top undergraduate and graduate students in the department.

聚烯烃包括经济和技术上重要的材料类别。作为所有聚合物的子集，它们是一般众所周知的，但是持续的持续改进的非全新世聚合催化表明，可以通过共聚，混合和混合材料和复合材料来增强物理特性。因此，聚集蛋白和它们的混合物涵盖了可能的应用的范围，从低成本一次性食品包装到航空航天结构设计的多组分复合材料。在所有情况下，不仅涉及纯聚合物，这是大多数混合物或复合材料的形态和局部结构，决定了材料的最终物理和性能特性。可言，对聚烯烃混合物的第一原理混合规则是不知道的，因此不知道，例如，诸如溶解溶解的溶解性诸如溶解的溶解性。 智力优点。在分子或链级别上，缺乏实验数据，即散装聚烯烃混合物中的链结构/混乱关系的距离远未实现。固体NMR实验可访问可访问的长度尺度的介观对介观的显微镜（即埃。通过获取特定于链的数据（动力学和距离），需要对链条填料和链结构的相对重要性进行长期存在的问题，可以检查每个问题在确定熵和焓贡献对整体相过程的贡献中的作用。 更广泛的影响。在这些非极性，非晶体的聚合物的混合物中，围绕聚烯相行为的基本科学问题，尤其是熔体或固态中的无定形聚集素的基本问题，构成了极限分子热力学的限制类别。因此，聚集蛋白及其混合物是对聚合物科学中一些长期问题的实验性研究的理想系统。例如，大晶聚集素是集中系统，具有许多自由度。鉴于可以使用聚芬素的链体结构，可以在分子之间和分子之间的不同自由度（理性的动态异质性波动的理性引入）与相行为/相变相关并相关？在构型熵参数的背景下，已经描述了像液晶中的无定形大分子（如液晶中的长度尺度和时间尺度）。我们可以使用散装聚集素及其蓝色，在局部链级（1-10 nm）上提供无创的实验确认吗？如果非相互作用分子中的玻璃形成是由构型术的丧失驱动的，那么分子水平（小于回旋的聚合物半径）是否可以检测并定义局部TG？该数据是否可以用来帮助扩大聚合物相行为的当前热力学模型的范围，以包括配置熵贡献？ PI曾经并且将继续是该项目通过该项目的各个教育的积极参与者。 PI通过NCSU化学系的公共外展总监竭尽全力，在小学，中学和高中场所提出了物理科学，和聚合物科学的多次演示。此外，该项目的构成学科方面（光谱，聚合物化学，聚合物物理学，材料科学）继续吸引该系的顶级本科生和研究生。