Chain Dynamics and Layering within Polyelectrolyte Multilayer Films

技术概述：逐层聚电解质膜的分层是聚电解质多层膜(PEM)先进的生物医学和光学应用的核心，但常常受到分子扩散和混合的影响。在这个项目中，我们将探索聚合物链动力学与质子交换膜内部结构之间的基本关系，并将利用这些知识来开发层状LBLPEM膜的构建策略，并研究其结构在老化过程中的演变。具体地说，将在三种情况下探索链间动力学：(1)在溶液中；(2)在多层结构中的溶液和薄膜之间；以及(3)在潮湿或水环境中老化的LBL薄膜的组装后步骤。对于情况(1)-(3)，将分别应用荧光相关光谱(FCS)、FCS和原位ATR-FTIR的组合以及图案光漂白后的荧光恢复(FRAPP)和中子反射率(NR)的组合。该项目涉及通过离子配对或氢键结合的定义明确的聚碱-聚酸(PB-PA)对的合成。中心建议是聚合物在PEMS中的平移扩散是各向异性的，所提出的实验旨在揭示这种各向异性的程度，以及当PEM薄膜在高湿度环境中或在不同温度和/或离子强度的水溶液中老化时，这种各向异性是如何随时间演变的。该方案中产生的知识可用于预测广泛的PEM膜中的相互作用、运动、松弛和有序性。非技术概述：该项目提供了自组装聚合物膜的动力学和结构知识，这将使生物医学和光学应用的分层聚合物膜的构建和老化预测成为可能。一个例子包括能够从生物医学装置或植入物表面顺序输送治疗性化合物的聚合物涂层。重要的是，这个项目将为参与的研究生和暑期本科生在聚合物科学的前沿问题上创造一个肥沃的训练场，通过与NIST和ORNL的合作进一步丰富这个训练场。作为高度跨学科的史蒂文斯纳米技术研究生计划的一部分，将开发一门关于纳米结构聚合物的新课程。该项目的一个重要部分包括与新泽西州北部地区的高中生合作，并通过实验演示和有K-12高中生参加的海报展览来传播知识。通过与K-12 ACS SEED和新泽西科学伙伴计划现有的密切联系，将开发一项新的教育倡议。具体地说，通过与NSF资助的GK-12计划、新泽西工程教育联盟(NJAEE)以及史蒂文斯工程和科学教育创新中心(CIESE)合作，将建立一个教学模块，并在高中环境中进行试点。该模块将在NJAEE网站上展示，并链接到CIESE网站，该网站每年有数十万名K-12教育工作者和学生访问该网站。

TECHNICAL SUMMARY:Stratification of layer-by-layer (LbL) polyelectrolyte films lies in the heart of advanced biomedical and optical applications of polyelectrolyte multilayer (PEM) films, yet is often compromised by molecular diffusion and intermixing. In this project, fundamental correlations between dynamics of polymer chains and internal structure of PEMs will be explored, and this knowledge will be applied to develop strategies for the construction of stratified LbL PEM films and to study evolution of their structure during aging. Specifically, inter-chain dynamics will be explored in three cases: (1) in solution; (2) between solution and the films during multilayer construction; and (3) at a post-assembly step during aging of LBL films in humid or aqueous environments. Fluorescence correlation spectroscopy (FCS), a combination of FCS and in situ ATR-FTIR, and a combination of fluorescence recovery after pattern photobleaching (FRAPP) and neutron reflectivity (NR) will be applied for cases (1)- (3), respectively. The project involves synthesis of well-defined polybase-polyacid (PB-PA) pairs associated through ionic pairing or hydrogen-bonding. The central suggestion is that translational diffusion of polymers within PEMs is anisotropic, and proposed experiments aim to reveal the degree of this anisotropy as well as how this anisotropy evolves with time when PEM films are aged in high humidity environment or in aqueous solutions under varying temperature and/or ionic strength. The knowledge generated in this proposal can be used to predict interactions, motions, relaxations and order in a broad range of PEM films.NON-TECHNICAL SUMMARY:This project provides knowledge of dynamics and structure of self-assembled polymer films, which will enable construction and prediction of aging of stratified polymer films for biomedical and optical applications. One example includes polymer coatings enabling sequential delivery of therapeutic compounds from the surface of a biomedical device or an implant. Importantly, this project will create a fertile training ground for the participating graduate students and summer undergraduate students in forefront issues of polymer science, a training ground further enriched by collaboration with NIST and ORNL. A new course on nanostructured polymers will be developed as part of the highly interdisciplinary Stevens Nanotechnology Graduate Program. A significant part of the project includes working with high school students from the Northern New Jersey area and disseminating knowledge through experimental demonstrations and poster exhibition involving K-12 high school students. Through existing close links with the K-12 ACS SEED and the Partners in Science Program NJ program, a new educational initiative will be developed. Specifically, by working with a recently started NSF-funded GK-12 initiative, New Jersey Alliance for Engineering Education (NJAEE), and with the Stevens Center for Innovation in Engineering and Science Education (CIESE), a teaching module Polymers in Our Life will be built and piloted in a high school setting. The module will be featured on the NJAEE website, and linked to the CIESE website, which enjoys hundreds of thousands of site visits by K-12 educators and students each year.