Effect of Stress Relief and Ionic Charge on Polyelectrolyte Brush Behavior

应力消除和离子电荷对聚电解质刷行为的影响

基本信息

批准号：
1709660
负责人：
Christopher Ober
金额：
$ 38.91万
依托单位：
Cornell University
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2017
资助国家：
美国
起止时间：
2017-08-01 至 2020-07-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1709660&HistoricalAwards=false
关键词：
Effect Stress Relief Ionic Charge

项目摘要

Polymers are large molecules formed by linking together hundreds of small molecular sub-units called monomers into long chains. Depending upon on the chemical structure of the monomer, the polymer can either be slippery (like Teflon) or sticky (like tape). By changing the monomer, one can create surfaces that prevent adhesion of cells, making them better for medical uses. Nature accomplishes this by attaching charged polymer segments to surfaces, forming structures that resemble brushes. While these brush polymers offer unique properties that could have substantive societal impacts, they also pose significant challenges. The dense packing of the charged groups can stretch the chemical bonds and, in extreme cases, the bonds can break. With the support of the Macromolecular, Supramolecular and Nanochemistry program of the Chemistry Division, Professor Ober at Cornell University is creating and studying new polymer brushes that are effective coatings but also have long lifetimes (i.e., do not have bonds that easily break). Collaborators, Professor Ryan (University of Sheffield) and Professor Ruehe (University of Freiburg), are helping to characterize the polymer structures. In addition to its scientific impact, the project benefits society by educating undergraduate and graduate students to become globally aware, interdisciplinary scientists. Surface-bound bottlebrush polymers are potentially synthetic mimics for shock absorbing components in the human body, thus, the broader scientific impact of this project outside of macromolecular chemistry is potentially quite large. Insights into the polyelectrolyte brush behavior may also help in the understanding the attachment of biomolecules, cells and microorganisms to surfaces and thus be used to control into unwanted adhesions on ships for the marine industry.The research team is creating and studying a series of stable model polymer brushes with carefully tailored placement of ionic groups in both single strand and bottlebrush architectures. Physical phenomena associated with charge, binding and attachment of soluble species, and the rather unusual case of mechanochemistry that leads to brush breakage are being investigated. Professor Ober and his collaborators are preparing specially tailored polyelectrolyte brushes with selected vertical and horizontal brush architectures and studying their physical properties. Ionic groups are attached directly to the acrylate or methacrylate polymer backbone or through tailored sequences of peptoid units of precise ionic group spacing and location. Confinement is controlled by the use of nanopatterning in which the pattern sizes are comparable to brush height (tens of nanometers). The effect of cation charge is studied using a range of mono- and multivalent cations. Characterization activities include: X-ray scattering studies of brush swelling and shrinkage under a range of wetting and electrolyte conditions and neutron reflectivity studies using labeled polymer chains to separately gather information about the different components (backbone, sidearm, ions) to develop a detailed picture of the charged polymer brush. Graduate students serve as mentors and role models to undergraduate students, while at the same time gaining supervisory skills. Undergraduates from Cornell University take part during the academic year while REU students from other schools with an emphasis onunderrepresented students participate in research during the summer months. Lessons learned from these research programs are integrated into lessons for high school teachers in a Research Experiences for Teachers (RET) program and in teachers' workshops.

聚合物是通过将数百个称为单体的小分子亚单元连接成长链而形成的大分子。根据单体的化学结构，聚合物可以是光滑的（如聚四氟乙烯）或粘性的（如胶带）。通过改变单体，人们可以创造出防止细胞粘附的表面，从而使其更适合医疗用途。大自然通过将带电聚合物片段附着在表面上，形成类似于刷子的结构来实现这一点。虽然这些刷状聚合物具有独特的性能，可能会产生实质性的社会影响，但它们也带来了重大挑战。带电基团的密集堆积会拉伸化学键，在极端情况下，化学键可能会断裂。在化学系高分子、超分子和纳米化学项目的支持下，康奈尔大学的奥伯教授正在创造和研究新型聚合物刷，这种刷是有效的涂层，但也具有较长的使用寿命（即没有容易断裂的键）。合作者 Ryan 教授（谢菲尔德大学）和 Ruehe 教授（弗莱堡大学）正在帮助表征聚合物结构。除了其科学影响之外，该项目还通过教育本科生和研究生成为具有全球意识的跨学科科学家来造福社会。表面结合的洗瓶刷聚合物可能是人体减震成分的合成模拟物，因此，该项目在大分子化学之外的更广泛的科学影响可能相当大。对聚电解质刷行为的深入了解也可能有助于了解生物分子、细胞和微生物在表面上的附着，从而可用于控制海洋工业船舶上不必要的粘附。研究团队正在创建和研究一系列稳定模型聚合物刷，在单链和瓶刷结构中均具有精心定制的离子基团位置。与可溶性物质的电荷、结合和附着相关的物理现象，以及导致刷子断裂的相当不寻常的机械化学案例正在被研究。奥伯教授和他的合作者正在准备具有选定的垂直和水平刷结构的专门定制的聚电解质刷，并研究它们的物理特性。离子基团直接连接到丙烯酸酯或甲基丙烯酸酯聚合物主链上，或者通过具有精确离子基团间距和位置的类肽单元的定制序列连接。通过使用纳米图案来控制限制，其中图案尺寸与刷子高度（数十纳米）相当。使用一系列单价和多价阳离子研究阳离子电荷的影响。表征活动包括：在一系列润湿和电解质条件下对刷子膨胀和收缩进行 X 射线散射研究，以及使用标记的聚合物链进行中子反射率研究，分别收集有关不同成分（主链、侧臂、离子）的信息，以绘制详细的图像带电聚合物刷。研究生充当本科生的导师和榜样，同时获得监督技能。康奈尔大学的本科生在学年期间参与研究，而来自其他学校的 REU 学生（重点是代表性不足的学生）则在夏季参与研究。从这些研究项目中汲取的经验教训被纳入教师研究经验 (RET) 项目和教师研讨会中为高中教师提供的课程中。