Effect of Extreme Nanoconfinement on the Thermodynamics and Transport Phenomena in Multiphasic Nanocomposite Coatings

由于其柔韧性、低密度和可回收性，聚合物薄膜和涂层在调节气体传输方面发挥着越来越重要的作用，在食品、饮料、微电子和医疗器械包装的气体屏障等广泛应用中。添加纳米颗粒和/或混合多种聚合物已被证明是调整纳米复合膜气体输运特性的有效方法。特别是，添加高浓度的纳米颗粒是生产高性能气体屏障和气体分离膜的有力方法。在这项工作中，研究人员将通过溶剂驱动的聚合物渗透（SIP）到纳米颗粒层中来生产具有高纳米颗粒负载的聚合物薄膜。在这个过程中，纳米粒子层，位于聚合物层的顶部，被溶剂填充。其中一些溶剂进入聚合物层，软化或塑化聚合物材料。一旦聚合物被塑化，它就可以通过与溶剂或纳米颗粒的相互作用，进入纳米颗粒层，填补纳米颗粒之间的空隙。研究人员将研究这些相互作用中的哪一种对聚合物渗透最重要，以及如何调整这些相互作用以获得具有高负载纳米颗粒的聚合物薄膜。这些坚硬的固体纳米颗粒保持着限制聚合物膨胀能力的屏障。这些约束聚合物有望表现出改善的气体屏障性能，使它们对各种包装应用具有吸引力。研究人员假设，在极端纳米约束下，纳米颗粒填料间隙中的聚合物链的动力学和热力学将由界面热力学主导。聚合物的溶剂渗透（SIP）为表征聚合物的动力学和热力学以及气体分子在极端纳米约束下通过二元聚合物相的输运提供了理想的平台。这项工作将导致对聚合物-溶剂-纳米颗粒相互作用如何影响渗透机制和动力学的基本理解，以及聚合物在极端纳米约束下的热力学。本文将利用原位椭偏光谱和分子动力学（MD）模拟来研究SIP的动力学和结构。有效的场理论模拟，包括自洽场理论，将用于理解填料中的热力学，并指导实验和MD模拟。通过透射电子显微镜、MD对SIP纳米复合材料的结构进行表征，并通过带耗散的石英晶体微天平测试其输运性能，建立不同聚合物分子量和聚合物-纳米颗粒相互作用下SIP纳米复合材料的结构-输运性能关系。由于目前还没有预测SIP动力学和热力学的理论框架，因此只要有可能，基于计算的方法将为实验条件提供重要的指导。调查人员将通过领导与波多黎各-胡马考大学、推进工程妇女和路易斯-斯托克少数民族参与联盟以及瑞秋莱夫学者计划的合作，支持未被充分代表的少数民族学生的参与。pi还计划开发教育项目和展览，在本科生/研究生的帮助下，展示具有超高天然纳米材料负载的纳米复合材料，用于通过当地高中和科学咖啡馆组织的外展活动。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Due to their flexibility, low density and recyclability, polymer films and coatings are playing an increasingly important role in the regulation of gas transport in a wide range of applications such as gas barriers for food, beverage, microelectronics and medical device packaging. Adding nanoparticles and/or blending multiple polymers together have proven to be effective methods to tune gas transport properties of nanocomposite films. Adding high concentrations of nanoparticles, in particular, is a powerful approach for producing high performance gas barriers and gas separation membranes. In this work the investigators will produce polymer films with high nanoparticle loadings via solvent-driven infiltration of polymers (SIP) into layers of nanoparticles. In this process, layers of nanoparticles, sitting on top of a polymer layer, are filled with a solvent. Some of this solvent moves into the polymer layer and softens or plasticizes, the polymer material. Once the polymer is plasticized, it can move into the nanoparticle layer, filling in the gaps between nanoparticles, by attractive interactions with either the solvent or the nanoparticles. The investigators will study which of these interactions are most important for polymer infiltration and how to tune these interactions to obtain polymer films with high loadings of nanoparticles. These hard, solid nanoparticles maintain barriers which limit polymer's ability to expand. These constrained polymers are expected to exhibit improved gas barrier properties, making them attractive for various packaging applications.The investigators hypothesize the dynamics and thermodynamics of polymer chains in the interstices of nanoparticle packings under extreme nanoconfinement will be dominated by the thermodynamics of the interfaces. Solvent-infiltration of polymers (SIP) provides an ideal platform to characterize the dynamics and thermodynamics of confined polymers and transport of gas molecules through a binary polymer phase under extreme nanoconfinement. This work will lead to fundamental understandings of how polymer-solvent-nanoparticle interactions affect the infiltration mechanism and dynamics, as well as the thermodynamics of polymers under extreme nanoconfinement. The dynamics and resulting structure of SIP will be studied using in situ spectroscopic ellipsometry as well as molecular dynamics (MD) simulations. Efficient field-theoretic simulations, including self-consistent field theory, will be used to understand the thermodynamics in the packings and guide both the experiments and MD simulations. The structure-transport property relationship of SIP nanocomposites for different polymer molecular weight and polymer-nanoparticle interactions will be established by characterizing the structure using transmission electron microscopy, MD, and by testing the transport properties through quartz crystal microbalance with dissipation. Because theoretical frameworks to predict the dynamics and thermodynamics of SIP are not currently available, whenever possible, computation-based approaches will provide important guidelines for experimental conditions. The investigators will support involvement from underrepresented minority students by leading cooperative efforts with University of Puerto Rico-Humacao, Advancing Women in Engineering and Louise-Stoke Alliance for Minority Participation and Rachleff Scholars Program. The PIs also plan to develop educational programs and exhibits that showcase the nanocomposites with ultra-high loadings of natural nanomaterials with the help of undergraduate/graduate students for use during outreach activities organized through local high schools and science cafe events.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.