Macromolecular Spreading

技术概述：聚合物流体在固体表面上扩散时的宏观行为已经被很好地理解，但我们对扩散的分子机制的理解仍然不完整和有争议。微观知识的缺乏现在是一个紧迫的问题，限制了各种微技术的发展，其特征时间和长度尺度正在接近单个分子。该计划的目标是对表面受限大分子的动力学、构象和化学结构的润湿引起的变化有一个基本的了解。具体来说，资助的研究将集中在(i)流动诱导的分子扩散，直接影响流动中大分子的排序、混合和化学反应；（ii）开发用于压力梯度和摩擦系数定量测量的分子传感器，这将有助于了解表面冷凝蒸汽对扩散机理和流速的润滑作用；最后（iii）高支化大分子的湿化降解。最后的重点打开了一个全新的途径，在反应性和功能领域的吸附大分子。初步看来，Sheiko小组在分子尺度的流动结构实验研究上取得了突破。通过分子可视化，我们发现流动的大分子通过改变其二级和一级结构来积极响应界面性质的变化。先前的工作为新方法的发展奠定了基础，该方法将为研究和控制100纳米以下薄膜中的流动提供大量机会。非技术概要：分子薄聚合物薄膜的流动特性影响涂层、复合材料、微流体和润滑。该计划将促进对表面受限聚合物链的构象和动力学的基本理解，并导致在分子长度尺度上控制流动的新技术的发展。这项工作也将导致阐明聚合物结构对润湿动力学的影响。该项目将为研究生和本科生提供跨学科的研究训练，因为它结合了精细的聚合物化学和先进的实验技术。其中一个战略目标是将分子可视化带到大学和高中的课堂上，在那里，看到分子的能力对于教授聚合物分子的反应机制和构象是无价的。分子可视化将作为新的实验模块添加到聚合物课程中，并在当地高中的定期科学研讨会上用作演示工具。

TECHNICAL SUMMARY: The macroscopic behavior of polymer fluids during spreading on solid surfaces is well understood, yet our understanding of the molecular mechanism of spreading remains incomplete and controversial. This lack of microscopic knowledge is now an urgent problem limiting developments in various microtechnologies, whose characteristic time and length scales are approaching those of individual molecules. The goal of this program is to achieve a fundamental understanding of the wetting-induced changes in the dynamics, conformation, and chemical structure of surface-confined macromolecules. Specifically, the funded research will focus on (i) the flow-induced molecular diffusion with direct implications to ordering, mixing, and chemical reactions of macromolecules in flow; (ii) the development of molecular sensors for quantitative measurements of the pressure gradient and friction coefficient, which will lead to understanding of the lubrication effect of surface-condensed vapors on the spreading mechanism and flow rate; and finally (iii) the wetting-induced degradation of highly branched macromolecules. The final focus opens an entirely new avenue in the field of reactivity and functioning of adsorbed macromolecules. Preliminary, the Sheiko group has achieved a breakthrough in experimental studies of the flow structure on the molecular scale. Through molecular visualization, it was demonstrated that flowing macromolecules actively responded to variations in the interfacial properties through changes in both their secondary and primary structures. The previous work set the foundation for the development of a new methodology that will open a vast array of opportunities to both study and control the flow in thin films on the scale below 100 nm. NON-TECHNICAL SUMMARY: The flow properties of molecularly thin polymer films impact coatings, composites, microfluidics, and lubrication. This program will advance fundamental understanding of the conformation and dynamics of surface-confined polymer chains and lead to the development of new technologies for controlling flow on molecular length scales. This work will also lead to elucidation of the effect of the polymer architecture on the wetting kinetics. The program will provide interdisciplinary research training for graduate and undergraduate students, since it combines fine polymer chemistry and advanced experimental techniques. One of the strategic goals is to bring molecular visualization to university and high-school classrooms where the ability to see molecules would be invaluable for the teaching of reaction mechanisms and conformation of polymer molecules. Molecular visualization will be added to polymer courses as new laboratory module and also used as a demonstration tool during regular scientific seminars at the local high schools.