Polyelectrolyte brushes: Stabilization through Controlled Charge Placement

聚电解质刷：通过控制电荷放置实现稳定

• 批准号: 2003588
• 负责人: Christopher Ober
• 金额: $ 44.28万
• 依托单位: Cornell University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-08-01 至 2023-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2003588&HistoricalAwards=false
• 关键词: Polyelectrolyte; brushes; Stabilization; through; Controlled

In this project funded by the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry, Professor Christopher K. Ober at Cornell University is developing and studying polyelectrolyte brushes with controlled charged placement. Polymer brushes are special, large molecular structures with polymer chains densely tethered to a surface. They have unique and useful properties including wormlike conformation, compact molecular dimensions, and notable polymer chain end effects due to their compact and confined structures. These particular polyelectrolyte brushes can interact with a biological environment actively or passively depending on the nature of a living system. As such, the brushes are promising materials for biomedical devices, chemical sensors and drug-delivery systems. In this research, synthetic methods are chosen to construct charged polyelectrolyte brushes, allowing systematic investigations of how charge placements changs the swelling, shape, mobility, and stability of the synthesized brushes. Characterization is carried out using sophisticated chemical measurement techniques and also includes the effect of solution acidity and metal ions on brush behavior. This research is interdisciplinary in nature and includes international collaborations with researchers in Germany and the United Kingdom. The research program exposes graduate students and associated researchers to international science perspectives. Graduate students serve as mentors and role models to undergraduate students, while at the same time gaini supervisory skills. Undergraduates from Cornell University take part in the research during the academic year while students from other schools with an emphasis on underrepresented communities participate in research during the summer months. Outreach activities include high school students and teachers through organized workshops. This research is focused on the preparation and study of a series of model poly(electrolyte)(PEL) brushes with carefully tailored placement of cationic and anionic groups used either alone or in combination in a single strand and bottle brush architecture based on acrylamide and styrene-maleimide polymers. Characterization includes study of the effect of pH and metal ions on brush behavior of these new architecture PEL brushes. Neutron and X-ray reflectometry studies of swollen polymer films are used as tools for understanding brush behavior. Neutron reflectivity using labeled polymer chains to separately gather information about the different components (brush, sidearm, ions) of the polymer brush is also employed. Brushes are grown from surfaces by means of controlled radical polymerization of charged or protected monomers. Ionic groups are attached to acrylamide or maleimide backbones through tailored amine functional segments including peptoid units of selected lengths and ionic group content. Longer peptoid side chains on a polymer backbone form bottle brush-like architectures while controlled charge spacing and location selectively add coulombic stress near to or away from the polymer backbone. In addition to conventional vertically grown brushes, the research team is capitalizing on new lateral brush growth geometries through demonstrated microfabrication capabilities that enable parallel optical and X-ray or optical and neutron characterization of brush swelling under a range of wetting and electrolyte conditions. This research addresses important questions on the conformation of dense polyelectrolyte brushes, including the effects of chain confinement and charge spacing. The results have the potential to further advance fundamental understanding of the factors affecting the stability and stimulus-responsive nature of surface-grafted bottlebrush polymers.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.

在这个由化学系高分子、超分子和纳米化学项目资助的项目中，康奈尔大学的 Christopher K. Ober 教授正在开发和研究具有受控电荷放置的聚电解质刷。 聚合物刷是特殊的大分子结构，聚合物链密集地束缚在表面上。 它们具有独特且有用的特性，包括蠕虫状构象、紧凑的分子尺寸以及由于其紧凑和受限的结构而显着的聚合物链末端效应。 这些特殊的聚电解质刷可以根据生命系统的性质主动或被动地与生物环境相互作用。 因此，刷子是用于生物医学设备、化学传感器和药物输送系统的有前途的材料。 在这项研究中，选择合成方法来构建带电聚电解质刷，从而可以系统地研究电荷放置如何改变合成刷的膨胀、形状、迁移率和稳定性。 表征是使用复杂的化学测量技术进行的，还包括溶液酸度和金属离子对刷子行为的影响。 这项研究本质上是跨学科的，包括与德国和英国研究人员的国际合作。 该研究项目让研究生和相关研究人员了解国际科学观点。 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，而其他重点关注弱势群体的学校的学生则在夏季参与研究。 通过举办研讨会，向高中生和教师开展外展活动。 这项研究的重点是制备和研究一系列模型聚（电解质）（PEL）刷，这些刷具有精心定制的阳离子和阴离子基团的位置，可以单独使用，也可以在基于丙烯酰胺和苯乙烯-马来酰亚胺聚合物的单股和瓶刷结构中组合使用。 表征包括研究 pH 值和金属离子对这些新架构 PEL 刷的刷行为的影响。 溶胀聚合物薄膜的中子和 X 射线反射测量研究被用作了解刷子行为的工具。 还采用中子反射率，使用标记的聚合物链来单独收集有关聚合物刷的不同组件（刷、侧臂、离子）的信息。 刷子是通过带电或受保护单体的受控自由基聚合从表面生长的。 离子基团通过定制的胺功能片段（包括选定长度和离子基团含量的类肽单元）连接到丙烯酰胺或马来酰亚胺主链上。 聚合物主链上较长的类肽侧链形成瓶刷状结构，同时受控的电荷间距和位置选择性地增加靠近或远离聚合物主链的库仑应力。 除了传统的垂直生长的刷子之外，研究团队还通过展示的微加工能力利用新的横向刷子生长几何形状，这些能力能够在一系列润湿和电解质条件下对刷子膨胀进行并行光学和X射线或光学和中子表征。 这项研究解决了致密聚电解质刷构象的重要问题，包括链限制和电荷间距的影响。 这些结果有可能进一步促进对影响表面接枝瓶刷聚合物的稳定性和刺激响应性质的因素的基本理解。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。