Effect of Chain-ends on the Mixed Polymer Brush Morphology

链端对混合聚合物刷形态的影响

基本信息

批准号：
2003891
负责人：
Padma Gopalan
金额：
$ 45万
依托单位：
University of Wisconsin-Madison
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2020
资助国家：
美国
起止时间：
2020-07-01 至 2024-06-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=2003891&HistoricalAwards=false
关键词：
Effect Chain ends Mixed Polymer

项目摘要

PART 1: NON-TECHNICAL SUMMARYPolymer brushes are long stringy molecules that are chemically anchored to a surface to form a dense, thin coating that alters the surface properties. While the chemical anchoring to the surface provides the required mechanical strength to the coating, the chemistry and structure of the polymer enables communication with the environment. Hence, these coatings have broad relevance in solving problems in materials science and in human health. They can act as sensors for rapid detection of biomarkers in biofluids when anchored to electronically active surfaces, direct cell growth for regenerative medicine, resist deposition of micro-organisms on surfaces, control flow of charge in batteries, control friction at relevant interfaces., etc. This research program will develop new synthetic methodologies to make these polymer brushes with well defined structure and chemistry. The methodology developed is high yielding, simple and reproducible on a wide range of surfaces, hence can be adapted by the coating industry. This program will develop characterization methods to aid in the molecular level understanding of the resulting structure. The research program will serve to inspire and involve undergraduate students in polymer science and engineering research, by working with graduate student mentors, through the REU program. Educational modules will also be developed for dissemination through UW-Madison’s institute for Chemical Education, a national center dedicated to STEM education through outreach and education research. PART 2: TECHNICAL SUMMARYThe research program will develop a highly versatile approach to grow mixed A/B polymer brushes from a substrate using a cross-linkable copolymer coating, which contains a polymerizable initiator (inimer) as a comonomer. Mixed A/B polymer brushes consist of chemically distinct A and B chains, randomly grafted to the surface. They show changing density, height and composition profile as a function of solvent environment. These polymer brushes will have high chain grafting density, uniform distribution of A and B graft points, controlled molecular weights, and excellent control over composition. Theory predicts the lowering of critical point for phase separation in mixed brushes compared to block copolymers, and the formation of nanoscale morphology. However, experimental studies have fallen short of validating these predictions. The gap between theory and experiments is attributable to lack of: a) experimental methods for uniform growth of high grafting density mixed brushes with controllable grafting ratios, and predictable chain lengths, (b) accounting for chain end-groups in theory and experiments, and (c) characterization methods to study the morphology. In this project the goal is to understand the role of chain-end density, size, distribution, and type on the A/B mixed brush morphology. This is a largely experimentally and theoretically unexplored area in polymer brushes. Key aspects of this research will be to develop synthetic strategies to append select chain end groups, quantification of the extent of functionalization and chain-end distribution by a combination of X-ray photoelectron spectroscopy and Resonant Soft X-ray scattering (RSoXS), and studying the effect of chain-end functionalization on lateral phase segregation by a combination of scattering and advanced microscopy techniques. The morphological insight developed through these experiments will contribute towards the broader understanding and application of polymer brushes..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.

第 1 部分：非技术摘要聚合物刷是长丝状分子，通过化学方式固定在表面上，形成致密的薄涂层，从而改变表面特性。因此，这些涂层在解决材料科学和人类健康问题方面具有广泛的相关性，当固定在电子上时，它们可以充当快速检测生物流体中生物标记物的传感器。活性表面、再生医学的直接细胞生长、抵抗微生物在表面上的沉积、控制电池中的电荷流动、控制相关界面的摩擦等。该研究计划将开发新的合成方法，使这些聚合物刷具有良好的性能所开发的方法产量高、简单且在各种表面上可重复，因此该计划将开发表征方法以帮助对所得结构进行分子水平的理解。计划将有助于激发和通过 REU 计划，让本科生参与聚合物科学和工程研究，并与研究生导师合作，还将开发教育模块，并通过威斯康星大学麦迪逊分校化学教育研究所进行传播，该研究所是一个致力于通过外展和教育进行 STEM 教育的国家中心。研究第 2 部分：技术概要该研究计划将开发一种高度通用的方法，使用包含可聚合引发剂的可交联共聚物涂层从基材上生长混合 A/B 聚合物刷。混合 A/B 聚合物刷由化学上不同的 A 链和 B 链组成，随机接枝到表面，它们的密度、高度和成分分布随溶剂环境的变化而变化。链接枝密度、A 和 B 接枝点的均匀分布、可控的分子量以及对组成的出色控制。理论预测，与嵌段共聚物相比，混合刷的相分离临界点会降低，并且会形成纳米级形态。实验研究未能验证这些预测，其原因在于缺乏：a）具有可控接枝率和可预测链长的高接枝密度混合刷的均匀生长的实验方法，（b）考虑到链端基的理论和实验，以及 (c) 研究形态的表征方法在该项目中，目标是了解链端密度、尺寸、分布和类型对 A/B 混合刷形态的作用。 .这很大程度上是这项研究的关键方面是聚合物刷在实验和理论上尚未探索的领域，将开发合成策略以附加选择的链端基团，通过结合 X 射线光电子能谱和共振软技术来量化官能化程度和链端分布。 X 射线散射 (RSoXS)，并通过结合散射和先进的显微镜技术来研究链末端功能化对横向相分离的影响，通过这些实验开发的形态学见解将做出贡献。更广泛地理解和应用聚合物刷。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。