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.

在这项由化学系高分子、超分子和纳米化学计划资助的项目中，康奈尔大学的Christopher K.Ober教授正在开发和研究具有可控带电放置的聚电解质刷子。聚合物刷子是一种特殊的大分子结构，聚合物链密集地拴在一个表面上。由于其紧凑和受限的结构，它们具有独特和有用的性质，包括蠕虫状构象、紧密的分子尺寸和显著的聚合物链末端效应。这些特殊的聚电解质刷子可以主动或被动地与生物环境相互作用，这取决于生命系统的性质。因此，这种刷子很有希望成为生物医学设备、化学传感器和药物输送系统的材料。在这项研究中，选择合成方法来构建带电的聚电解质刷子，以便系统地研究电荷放置如何改变合成的刷子的膨胀、形状、流动性和稳定性。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。这项研究是跨学科的，包括与德国和英国的研究人员的国际合作。该研究计划让研究生和相关研究人员接触到国际科学的视角。研究生是本科生的导师和榜样，同时也获得了管理技能。康奈尔大学的本科生在学年期间参与研究，而其他学校的学生则在夏季几个月参与研究，这些学校侧重于代表性不足的社区。外展活动包括通过有组织的讲习班向高中生和教师宣传。这项研究致力于制备和研究一系列模型聚电解质(PEL)刷子，这些刷子精心定制地放置了阳离子和阴离子基团，无论是单独使用还是组合使用，都是基于丙烯酰胺和苯乙烯-马来酰亚胺聚合物的单链和瓶刷结构。表征包括研究pH值和金属离子对这些新结构的PEL刷子刷子行为的影响。膨胀聚合物膜的中子和X射线反射仪研究被用作了解刷子行为的工具。中子反射率使用标记的聚合物链来分别收集关于聚合物刷子的不同成分(刷子、侧臂、离子)的信息。刷子是通过带电或受保护的单体的受控自由基聚合从表面生长出来的。离子基团通过量身定制的胺功能段连接到丙烯酰胺或马来酰亚胺主链上，包括选定长度和离子基团含量的类肽单元。聚合物主链上较长的类肽侧链形成瓶刷状结构，而受控的电荷间距和位置选择性地在聚合物主链附近或远离聚合物主链增加库仑应力。除了传统的垂直生长刷子外，研究团队还通过展示的微制造能力，利用新的横向刷子生长几何形状，实现了在一系列润湿和电解液条件下对刷子膨胀的平行光学和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子构象的重要问题，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嫁接瓶刷聚合物的稳定性和刺激响应性的因素的基本理解。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。