Collaborative Research: Integrated experiments and simulations to understand the mechanism and consequences of polymer adsorption in films and nanocomposites

合作研究：综合实验和模拟来了解薄膜和纳米复合材料中聚合物吸附的机制和后果

• 批准号: 2312324
• 负责人: David Simmons
• 金额: $ 32.62万
• 依托单位: University of South Florida
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-07-01 至 2026-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2312324&HistoricalAwards=false
• 关键词: Collaborative; Research; Integrated; experiments; simulations

NON-TECHNICAL SUMMARY: From lightweight materials to flexible solar panels, the materials opening the door to tomorrow’s technologies frequently exhibit “nanostructure”: they are comprised of two finely intermixed domains only hundreds to thousands of atoms across. In many cases, one of these domains consists of polymers, which are long chains of molecules that plastics, rubber, and many biological materials are made of. In parallel, the second domain often consists of tiny inorganic nanoparticles – rigid regions that can dramatically enhance the polymers’ properties. Over the past decade, scientists have found evidence that something strange happens at the interfaces between these domains: the polymer molecules become tightly ‘glued’ to the particles at the molecular level. This process, known as “irreversible adsorption”, seems to dramatically alter these materials’ properties, with the potential to imbue tolerance of higher temperatures, to alter permeability, and perhaps to enhance mechanical strength. However, the cause of this effect – or even why it should occur at all – remains unknown. Even more practically, there is little understanding of how to control this irreversible adsorption phenomenon in order to obtain the best possible properties for next-generation materials. This collaborative project (co-supported by the Polymers Program and the Condensed Matter and Materials Theory Program in the Division of Materials Research) will combine experiments and computer simulations to understand why this adsorption effect occurs and how scientists and engineers can control it to optimize material properties. Experiments will employ a nanoscale characterization method wherein fluorescent probe molecules, localized to the nanoscale domain near the interface, report on the properties of the adsorbed layer and how it forms. Molecular simulations performed on supercomputers will zoom in to the molecular scale to understand how molecules move and evolve during irreversible adsorption, making it possible to link changes in material properties with underlying causes in molecular structure and motion. Together, these approaches aim to provide the fundamental scientific understanding needed to enable more rational engineering and design of these materials, with relevance to economic sectors ranging from infrastructure to energy. This research will be coupled with a new high-school internship program that will support broadening the pipeline of students moving into STEM professions.TECHNICAL SUMMARY: In polymer films and nanocomposites, the formation of an irreversibly adsorbed layer from the polymer melt can dramatically alter the properties of the interfacial domains that dominate the overall properties of these materials. Unlike in polymer adsorption from solution, which is driven by a combination of an energetic mismatch and an entropic size asymmetry between solvent and polymer, the thermodynamic mechanism of adsorption from the melt (where these factors are absent) remains unresolved. Moreover, numerous properties are reported to co-evolve during adsorption, challenging the development of a theory of adsorption accounting for all of them. A central challenge has been the difficulty of probing the evolution of near-substrate and near-particle properties in a temporally and spatially resolved manner during adsorbed layer formation. To overcome these challenges, this work will employ fluorescence experiments to locally probe the evolution of multiple properties near substrates and particles during adsorption. These experiments will be combined with molecular dynamics simulations that will provide spatially resolved insight into how segmental packing, chain conformations, and polymer dynamics co-evolve during adsorbed layer formation. Synergistic experiments and simulations will take an integrated approach to systematically probe the layer formation process, the behavior of isolated adsorbed layers, and the ultimate impact of the adsorbed layer presence on material properties, all across a matrix of key controlling variables. This strategy will establish an understanding of how multiple mechanisms may interact to drive adsorbed layer formation and mediate its impact on polymer properties..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：从轻巧的材料到柔性太阳能电池板，材料为明天的技术打开了经常暴露的“纳米结构”的材料：它们由两个细微的混合域组成，只有数百至数千原子。在许多情况下，这些结构域之一由聚合物组成，聚合物是塑料，橡胶和许多生物学材料的分子的长链。同时，第二个结构域通常由微小的无机纳米颗粒组成 - 刚性区域可以显着增强聚合物的性质。在过去的十年中，科学家发现证据表明这些域之间的界面发生了一些奇怪的事：聚合物分子在分子水平上紧密地“粘合”到颗粒上。这个被称为“不可逆吸附”的过程似乎会极大地改变这些材料的特性，并有可能赋予较高温度的耐受性，以改变渗透性，并可能提高机械强度。但是，这种效果的原因 - 甚至是为什么要发生的原因 - 仍然未知。更重要的是，几乎没有了解如何控制这种不可逆转的吸附现象，以便获得下一代材料的最佳特性。这个合作项目（由聚合物计划和材料研究部中的凝聚的物质和材料理论计划共同支持）将结合实验和计算机模拟，以了解为什么会出现这种增加的吸附效应以及科学家和工程师如何控制其以优化材料属性。实验将采用纳米级表征方法，其中荧光探针分子位于界面附近的纳米级结构域，报告吸附层的性质及其形成方式。在超级计算机上进行的分子模拟将缩小到分子尺度，以了解分子在不可逆的过程中如何移动和进化，从而可以将材料特性的变化与分子结构和运动中的基本原因联系起来。这些方法一起，旨在提供基本的科学理解，以实现这些材料的更多理性工程和设计，与从基础设施到能源的经济部门相关。这项研究将与一项新的高中实习计划结合起来，该计划将支持扩大进入STEM专业的学生的管道。技术摘要：在聚合物膜和纳米复合材料中，从聚合物融化的不可逆吸附层的形成可以极大地改变构造这些材料的属性属性的属性。与溶液的聚合物吸附不同，溶液是由溶解度和溶解性和聚合物之间的熵不匹配和熵尺寸不对称的组合驱动的，溶解度和聚合物之间的熵不对称性是从熔体中添加吸附的热力学机制（在这些因素不存在的情况下）保持尚未分辨。此外，据报道，许多属性在增加吸附过程中共同进化，挑战了对所有这些理论的发展。一个核心挑战是在吸附层形成期间以临时和空间分辨的方式探测近地基和近粒子特性的发展。为了克服这些挑战，这项工作将采用荧光实验来局部探测在吸附过程中底物和颗粒附近的多个特性的演变。这些实验将与分子动力学模拟结合使用，这些模拟将提供有关在吸附层形成过程中如何共同分段堆积，链构象和聚合物动力学共同进化的空间洞察力的。协同实验和仿真将采用一种集成的方法来系统地探测层的形成过程，隔离吸附层的行为以及吸附层的存在对材料属性的最终影响，这既跨越密钥控制变量的矩阵。该策略将对多种机制进行相互作用以推动吸附层的形成并调节其对聚合物特性的影响。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的知识分子和更广泛的影响来审查标准来支持的。