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.

在该项目中，由化学系的大分子，超分子和纳米化学计划资助，康奈尔大学的克里斯托弗·K·奥伯教授正在开发和研究具有控制装置的聚电解质刷。 聚合物刷是特殊的大分子结构，其聚合物链密集地系在表面上。 它们具有独特的和有用的特性，包括蠕虫状构象，紧凑的分子尺寸以及由于其紧凑和狭窄的结构而引起的显着聚合物链终极效应。 这些特定的聚电解质刷可以根据生命系统的性质积极或被动地与生物环境相互作用。 因此，刷子是生物医学设备，化学传感器和药物传递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的聚电解质刷，从而可以系统地研究电荷放置方式如何改变合成刷的肿胀，形状，迁移率和稳定性。 使用复杂的化学测量技术进行表征，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。 该研究计划使研究生和相关研究人员了解国际科学的观点。 研究生是本科生的导师和榜样，同时又是Gaini监督技能。 康奈尔大学的大学生在学年参加了研究，而其他学校的学生则强调代表性不足的社区在夏季的几个月中参加了研究。 外展活动包括高中生和教师通过有组织的研讨会。 这项研究的重点是对一系列模型聚（电解质）（PEL）刷的制备和研究，并精心量身定制的阳离子和阴离子组的放置单独使用或组合在基于丙烯酰胺和苯乙烯 - 甲酰亚胺聚合物的单链和瓶刷结构中。 表征包括研究pH和金属离子对这些新体系结构PEL刷的刷子行为的影响。 中子和X射线反映肿胀的聚合物膜的研究被用作理解刷子行为的工具。 还采用了使用标记的聚合物链的中子反射率，以分别收集有关聚合物刷的不同成分（刷子，侧臂，离子）的信息。 刷子是通过充电或受保护的单体的受控自由基聚合从表面生长的。 离子基通过量身定制的胺功能片段连接到丙烯酰胺或马来酰亚胺骨架上，包括所选长度和离子组含量的肽单元。 聚合物骨架上的较长的肽侧链形成瓶刷状结构，而受控的电荷间距和位置有选择地添加附近或远离聚合物骨架的库仑应力。 除了传统的垂直生长的刷子外，研究团队还通过展示的微作业能力来利用新的侧向刷生长几何形状，这些能力能够在一系列湿润和电解质条件下实现平行的光学和X射线或光学和中子表征。 这项研究解决了有关密集聚电解质刷的构象的重要问题，包括链条限制和电荷间距的影响。 该结果有可能进一步提高对影响稳定性和刺激响应性的因素的基本理解。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的智力优点和更广泛影响的评估标准来评估的。