Quantifying Interactions Between Polyelectrolytes

非技术摘要：聚电解质是一种带电聚合物，广泛存在于自然界和制成品中。具有相反电荷的聚电解质相互结合，产生适合用作粘合剂、医用敷料、净化膜、受控药物释放载体和细胞培养支架的多功能软固体。这些所谓的“聚电解质复合体”也被发现是细胞内的无膜细胞器。尽管聚电解质复合体前景看好，并得到广泛应用，但目前尚不清楚为什么某些聚电解质组合可制成坚固的橡胶材料，而另一些组合则可产生粘性流体。这个项目将广泛地研究单个聚电解质的组成和它们形成的水化络合物的性质之间的基本关系。这一认识将指导新技术的已知材料和新材料的设计和应用。重视化学学生的教育和培训，包括扩大对STEM的参与，将使参与者接触到最新的想法、技术和解决问题的工具，以更好地服务于蓬勃发展的聚合物行业。学生参与有关聚电解质方面的高价值视频教程将接触到广泛的科学家受众，并将有助于培养参与培训的年轻学员的专业演示技能。技术摘要：当相反电荷的聚电解质Pol+和Pol-混合时，许多有趣和有用的非晶相自发地聚集在一起。然而，关于为什么不同的Pol+和Pol-组合具有显著不同的缔合强度，人们知之甚少。这项工作将定量和系统地探讨POL+/POL-缔合对“疏水性”或水分含量的依赖关系。利用稳健的合成方法，将制备和络合一系列疏水性越来越强的阳离子和阴离子聚合物。结合自由能将通过使用灵敏的放射性同位素或光谱学方法来确定，通过测量盐的添加有多容易破坏Pol+Pol-离子对。同时，将用红外光谱测定该复合体中的水量。结果将使缔合强度与水含量和为增强疏水性而添加的亚甲基单元的数量相关联。带电多肽之间的络合形成将揭示两个氨基酸之间形成的离子对或盐桥的结合强度。该项目产生的基本见解也将影响生物/健康领域，因为蛋白质的带电片段配对在蛋白质折叠(或错误折叠)中是必不可少的。在关于聚电解质相互作用的最后一项研究中，将测量聚电解质与具有特定表面组成的纳米颗粒之间的配对强度。佛罗里达州立大学GEOSET工作室提供的特殊教育资源将用于促进本科生和研究生的专业发展。本科生，特别是女化学家，将通过该大学的本科生研究计划招收，并将接受科学和演讲技能方面的指导。在研究小组以前的成功基础上，研究生们将合作制作几个关于聚电解质和聚电解质络合物的信息量大、竞争激烈、编辑精良的教学视频。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。

NON-TECHNICAL SUMMARY:Polyelectrolytes are charged polymers, found widely in nature and in manufactured goods. Polyelectrolytes with opposite charges associate with each other, yielding versatile, soft solids suited for use as adhesives, medical dressings, membranes for purification, carriers for controlled drug release, and scaffolds for cell culture. These so-called "polyelectrolyte complexes" have also been discovered as membrane-less organelles within cells. Despite the promise and prevalence of polyelectrolyte complexes, it is not known why some combinations of polyelectrolytes make strong, rubbery materials while other combinations produce viscous fluids. This project will investigate broadly the fundamental relationships between the composition of individual polyelectrolytes and the properties of the hydrated complexes they form. This understanding will guide the design and application of known and new materials for new technologies. An emphasis on chemistry student education and training, including broadening participation in STEM, will expose participants to the latest ideas, techniques and problem-solving tools to better serve the flourishing polymers industry. Student participation in high-value video tutorials on aspects of polyelectrolytes will reach a broad audience of scientists and will help build professional presentation skills of young trainees involved. TECHNICAL SUMMARY:A number of interesting and useful amorphous phases spontaneously assemble when polyelectrolytes of opposite charge, Pol+ and Pol-, are mixed. However, little is known concerning why different combinations of Pol+ and Pol- have substantially different association strengths. This work will quantitatively and systematically probe the dependence of Pol+/Pol- association on "hydrophobicity," or water content. Using robust synthetic methods, a series of increasingly hydrophobic cationic and anionic polymers will be prepared and complexed. The free energy of association will be determined by measuring, using sensitive radioisotope or spectroscopic methods, how easily Pol+Pol- ion pairs are broken by the addition of salt. At the same time, the amount of water in the complex will be determined with infrared spectroscopy. The results will correlate the strength of association to water content and number of methylene units added to enhance hydrophobicity. Complex formation between charged polypeptides will reveal the association strength of an ion pair or "salt bridge" formed between two amino acids. The fundamental insights resulting from the project will also impact the biological/health field since charged segment pairing of proteins is essential in protein folding (or misfolding). In a final thrust on polyelectrolyte interactions, the pairing strength between a polyelectrolyte and a nanoparticle of defined surface composition will be measured. The exceptional educational resources available at Florida State University's GEOSET studios will be employed to enhance the professional development of undergraduate and graduate students. Undergraduates, in particular women chemists, will be recruited through the University's undergrad research program and will be mentored in science and presentation skills. Building on previous successes within the research group, graduate students will collaborate to produce several informative, competitive, well-edited educational videos on polyelectrolytes and polyelectrolyte complexes.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.