Understanding the Impact of Confinement on the Dynamics of Entangled Chains

了解约束对纠缠链动力学的影响

• 批准号: 1808059
• 负责人: Gerald Schneider
• 金额: $ 36万
• 依托单位: Louisiana State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-08-01 至 2022-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1808059&HistoricalAwards=false
• 关键词: Understanding; Impact; Confinement; Dynamics; Entangled

NON-TECHNICAL SUMMARY:The variety and flexible properties of plastic materials (polymers) has changed our lives. The emergence of particles with a size as tiny as a billionth of a meter (nanoparticles) can provide even more flexible and stronger materials with superior properties as billions of these particles can be incorporated into polymers to yield nanocomposite materials. Modern chemistry can modify these nanoparticles at the molecular level, which leads to a substantial impact on their material behavior, often with unknown and novel properties. The challenge is to develop a relationship between molecular manipulations and macroscopic properties. This project approaches this task by controlling and varying the spatial distribution of the nanoparticles and by modifying the polymer molecules attached to the surfaces of these particles. The effects of nanoparticle confinement under these conditions will then be studied using advanced experimental techniques. The project includes the understanding of the relationship between mechanical properties of the nanocomposite materials and the spatial distribution of the nanoparticles, as well as the theoretical description at the molecular length-scale. This research is also integrated with education of students and exposing them to a variety of advanced experimental techniques.TECHNICAL SUMMARY:The effects imposed by nanoconfinement on polymer melts will be studied in this research. Emphasis will be on the manipulation of the chain dynamics by nanoparticle dispersion, surfaces, and the influence of chains grafted to surfaces. The current understanding is limited by knowledge gaps, which include a missing theoretical understanding of chain dynamics and how to distinguish effects of the particle dispersion and polymer chains. A holistic approach involving small-angle X-ray scattering (SAXS), dielectric spectroscopy (DS), and rheology, will be used to develop a theory based on recent progress to simultaneously describe the dielectric properties and rheology of polymer melts. Composites of NTPs (tethered chains on nanoparticles) dispersed in polymer matrices will be studied. The dispersion of the NTPs can be controlled by the grafting density, the molecular weight of free chains, and the corresponding characteristics of the NTPs. The static structure factor by SAXS can be used to obtain a phase map of systems with agglomerated and non-agglomerated particles, and to provide information on the length-scale of the confinement. The influence of the additional confinement imposed by nanoparticles on the chain dynamics will be explored, together with a change of the tube diameter of the polymer caused by surfaces.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

非技术摘要：塑料材料(聚合物)的种类和弹性改变了我们的生活。微小到十亿分之一米大小的颗粒(纳米颗粒)的出现可以提供更灵活、更坚固的材料，具有优越的性能，因为数十亿个这样的颗粒可以并入聚合物中，生成纳米复合材料。现代化学可以在分子水平上对这些纳米颗粒进行修饰，这会对它们的材料行为产生实质性的影响，往往具有未知和新颖的性质。挑战在于发展分子操纵和宏观性质之间的关系。该项目通过控制和改变纳米颗粒的空间分布，以及通过修改附着在这些颗粒表面的聚合物分子来实现这一任务。然后将使用先进的实验技术来研究在这些条件下纳米颗粒限制的效果。该项目包括了解纳米复合材料的力学性能与纳米颗粒的空间分布之间的关系，以及在分子长度尺度上的理论描述。这项研究还与学生的教育相结合，使他们接触到各种先进的实验技术。技术摘要：本研究将研究纳米限制对聚合物熔体的影响。重点将放在通过纳米粒子的分散、表面和接枝到表面的链的影响来操纵链的动力学。目前的理解受到知识差距的限制，包括缺乏对链动力学的理论理解，以及如何区分粒子分散和聚合物链的影响。小角X射线散射(SAXS)、介电能谱(DS)和流变学将被用来发展一种基于最新进展的同时描述聚合物熔体的介电性能和流变学的理论。我们将研究分散在聚合物基质中的NTP(纳米栓链)复合材料。接枝密度、自由链的相对分子质量以及相应的性质可以控制NTPs的分散性。SAXS的静态结构因子可以用来获得凝聚和非凝聚粒子系统的相图，并提供关于限制的长度-尺度的信息。我们将探讨纳米粒子施加的额外限制对链动力学的影响，以及表面引起的聚合物管径的变化。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

Uniqueness of relaxation times determined by dielectric spectroscopy

• DOI: 10.1088/1361-648x/acbcb8
• 发表时间: 2023-05-10
• 期刊: JOURNAL OF PHYSICS-CONDENSED MATTER
• 影响因子: 2.7
• 作者: Wu，Mengchun;Bichler，Karin J.;Schneider，Gerald J.
• 通讯作者: Schneider，Gerald J.

End block dynamics in unentangled polymers by dielectric spectroscopy

通过介电谱分析未缠结聚合物的末端嵌段动力学

• DOI: 10.1088/1361-648x/acdbf7
• 发表时间: 2023
• 期刊: Journal of Physics: Condensed Matter
• 作者: Wu, Mengchun;Bichler, Karin J;Jakobi, Bruno;Grzesiowski, Alyssa;Schneider, Gerald J
• 通讯作者: Schneider, Gerald J