Nonlinear Growth of Polyelectrolyte Multilayers: Chain Dynamics and Film Structure

聚电解质多层膜的非线性生长：链动力学和薄膜结构

• 批准号: 1610725
• 负责人: Svetlana Sukhishvili
• 金额: $ 42.37万
• 依托单位: Texas A&M Engineering Experiment Station
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-08-15 至 2019-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1610725&HistoricalAwards=false
• 关键词: Nonlinear; Growth; Polyelectrolyte; Multilayers; Chain

PART I: NON-TECHNICAL SUMMARY This project focuses on controlling the structure of functional polymer coatings. Such coatings could be used, e.g., for biomedical or optical applications. Examples might be coatings that can deliver drugs locally in a multi-stage, time-resolved protocol, or structured polymer films that can serve as precursors for better anti-reflective optical coatings. To support these advanced applications, (a) the coatings should be able to be easily deposited on a variety of surfaces via an environmentally friendly process, and (b) their structure should be easily controlled by the deposition procedure and conditions. The layer-by-layer (LbL) technique is a unique method which, through a deposition process entirely in water can create conformal coatings of controlled thickness on virtually any surface. The challenge, however, is to control the mixing of polymer molecules within the coated film to preserve film layering. This project will explore the effect of various molecular and deposition parameters on film layering, with the goal of achieving structured films which can be deposited through fewer steps. Advanced instrumental techniques will be used to take snapshots of how multilayered structures, water content, and film mechanical properties can be manipulated. Importantly, this project will create a fertile training ground for the participating graduate, undergraduate and high-school students. The PI is currently the academic advisor of the "Women in Materials Science" (WIMS) organization, which is strongly involved in many outreach activities, ranging from on-campus tours and demonstrations for Girl Scouts and high-school students to visits to local schools with the goal of encouraging and engaging female and minority 5-7th graders to pursue careers in science and engineering.PART II: TECHNICAL SUMMARYThe ability to control dynamics and the structure of layer-by-layer (LbL) polyelectrolyte films lies at the heart of advanced biomedical and optical applications of polyelectrolyte multilayer (PEM) films. Of specific interest are films with defined and controlled internal stratification. Yet nonlinearly growing LbL films (NL-LbLs) which deposit at larger thicknesses and therefore are highly desirable for many applications, suffer from molecular intermixing. This proposal aims to (a) uncover the mechanism of polymer chain diffusion within NL-PEMs during film growth, (b) establish correlations between molecular interactions, dynamics, and order for a broad range of NL-PEM films and (c) use this knowledge to control structure of NL-PEMs and develop strategies for constructing stratified and gradient LbL films. This project will involve synthesizing well-defined polybase-polyacid (PB-PA) pairs associated through ionic pairing or hydrogen-bonding. Interchain dynamics will be studied during PEM assembly, as well as at a post-assembly step. Neutron reflectometry (NR) will be used to track diffusion of polymer chains across the film thickness, in situ ellipsometry to determine film water content, and nanoindentation to explore film mechanical properties during film construction. At the post-assembly step, NR will be applied to resolve internal stratification, and fluorescence recovery after pattern photobleaching (FRAP) to study lateral mobility of assembled chains. This knowledge will then be used to rationally construct films with programmable density, water content, charge balance, and permeability. It will also enable rationally designed diffusional barriers and gradients of water content within NL-PEM films, in order to achieve films useful as matrices for conformal antireflective coatings or for sequential drug delivery via improved control of permeability of functional molecules.

第一部分：非技术性概述本项目的重点是控制功能性聚合物涂层的结构。这样的涂层可以用于，例如，用于生物医学或光学应用。 例子可能是可以在多阶段、时间分辨协议中局部递送药物的涂层，或者可以用作更好的抗反射光学涂层的前体的结构化聚合物膜。为了支持这些先进的应用，（a）涂层应该能够通过环境友好的工艺容易地沉积在各种表面上，以及（B）它们的结构应该容易地通过沉积程序和条件来控制。逐层（LbL）技术是一种独特的方法，通过完全在水中的沉积过程，可以在几乎任何表面上形成厚度可控的保形涂层。然而，挑战在于控制聚合物分子在涂布膜内的混合以保持膜分层。 该项目将探索各种分子和沉积参数对薄膜分层的影响，目标是通过更少的步骤获得结构化薄膜。先进的仪器技术将被用来拍摄如何操纵多层结构，水含量和薄膜机械性能的快照。重要的是，该项目将为参与的研究生、本科生和高中生创造一个肥沃的培训土壤。该组织积极参与许多外联活动，从为女童子军和高中生举办的校园图尔斯参观和示范活动，到访问当地学校，目的是鼓励和吸引5- 7年级的女生和少数民族学生从事科学和工程职业。控制逐层（LbL）多层膜的动力学和结构的能力是多层膜（PEM）的先进生物医学和光学应用的核心。特别感兴趣的是具有限定和控制的内部分层的膜。然而，非线性生长的LbL膜（NL-LbL）（其存款厚度较大，因此对于许多应用是非常理想的）遭受分子混合。该提案旨在（a）揭示膜生长过程中NL-PEM内聚合物链扩散的机制，（B）建立分子相互作用、动力学和大范围NL-PEM膜的有序性之间的相关性，以及（c）使用这些知识来控制NL-PEM的结构并开发用于构建分层和梯度LbL膜的策略。该项目将涉及合成通过离子配对或氢键结合的定义明确的多碱-多酸（PB-PA）对。链间动力学将在PEM组装过程中进行研究，以及在组装后的步骤。中子反射计（NR）将被用来跟踪整个膜厚度的聚合物链的扩散，在原位椭圆偏振法，以确定膜的水含量，和纳米压痕，以探索膜的机械性能在膜施工。在后组装步骤中，NR将用于解决内部分层，以及图案光漂白（FRAP）后的荧光恢复，以研究组装链的横向流动性。这些知识将用于合理地构建具有可编程密度、水含量、电荷平衡和渗透性的膜。它还将使得能够合理地设计NL-PEM膜内的扩散屏障和水含量梯度，以获得可用作保形抗反射涂层或用于通过改善控制功能分子的渗透性而顺序药物递送的基质的膜。