Quantifying Interactions Between Polyelectrolytes

非技术概述：聚电解质是带电聚合物，广泛存在于自然界和制成品中。带相反电荷的聚电解质相互结合，产生多功能的软固体，适合用作粘合剂、医用敷料、净化膜、控制药物释放的载体和细胞培养的支架。这些所谓的“多电解质复合物”也被发现是细胞内无膜的细胞器。尽管聚电解质复合物的前景和流行，但尚不清楚为什么一些聚电解质的组合可以制成坚固的橡胶材料，而另一些组合则会产生粘性流体。该项目将广泛研究单个聚电解质的组成及其形成的水合络合物的性质之间的基本关系。这种理解将指导新技术中已知和新材料的设计和应用。强调化学学生的教育和培训，包括扩大STEM的参与，将使参与者接触到最新的思想，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。学生参与关于聚电解质各方面的高价值视频教程将接触到广泛的科学家受众，并将有助于培养年轻学员的专业演讲技能。技术概述：当极性相反的聚电解质，Pol+和Pol-混合在一起时，一些有趣和有用的非晶态相自发地聚集在一起。然而，关于为什么Pol+和Pol-的不同组合具有本质上不同的结合强度，人们知之甚少。这项工作将定量和系统地探索Pol+/Pol-结合对“疏水性”或含水量的依赖。使用稳健的合成方法，一系列越来越疏水的阳离子和阴离子聚合物将被制备和络合。结合的自由能将通过测量，使用灵敏的放射性同位素或光谱方法，Pol+Pol-离子对是多么容易被加入盐破坏来确定。同时，用红外光谱法测定配合物中水的含量。结果将关联的强度与水的含量和亚甲基单位的增加，以提高疏水性的数量。带电荷多肽之间的络合物形成将揭示离子对的结合强度或两个氨基酸之间形成的“盐桥”。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。在聚电解质相互作用的最后推力中，将测量聚电解质和具有确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加强本科生和研究生的专业发展。本科生，特别是女化学家，将通过大学的本科研究项目招聘，并将在科学和演讲技巧方面得到指导。在研究小组之前成功的基础上，研究生们将合作制作一些关于聚电解质和聚电解质复合物的信息丰富、有竞争力、编辑良好的教育视频。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值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.