Quantifying Interactions Between Polyelectrolytes

非技术总结：聚电解质是带电聚合物，广泛存在于自然界和制成品中。具有相反电荷的聚电解质彼此缔合，产生多用途的软固体，其适合用作粘合剂、医用敷料、用于纯化的膜、用于控制药物释放的载体和用于细胞培养的支架。这些所谓的“膜复合物”也被发现是细胞内的无膜细胞器。尽管聚电解质复合物的前景和普遍性，但尚不清楚为什么聚电解质的某些组合产生坚固的橡胶材料，而其他组合产生粘性流体。该项目将广泛研究单个聚电解质的组成与它们形成的水合复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。对化学学生教育和培训的重视，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，以更好地为蓬勃发展的聚合物行业服务。学生参与高价值的视频教程方面的聚电解质将达到广大观众的科学家，并将有助于建立专业的演示技能的年轻学员参与。技术总结：当相反电荷的聚电解质Pol+和Pol-混合时，许多有趣且有用的无定形相自发地组装。然而，很少有人知道为什么Pol+和Pol-的不同组合具有显著不同的缔合强度。这项工作将定量和系统地探测Pol+/Pol-缔合对“疏水性”或水含量的依赖性。使用稳健的合成方法，将制备和复合一系列越来越疏水的阳离子和阴离子聚合物。缔合的自由能将通过使用灵敏的放射性同位素或光谱方法测量Pol+Pol-离子对被盐的加入破坏的容易程度来确定。同时，用红外光谱法测定络合物中的水量。结果将关联强度与水含量和添加以增强疏水性的亚甲基单元的数目相关联。带电多肽之间的复合物形成将揭示两个氨基酸之间形成的离子对或“盐桥”的缔合强度。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）中至关重要。在最后一个推力的纳米粒子相互作用，配对之间的强度的纳米粒子和确定的表面组成将被测量。特殊的教育资源可在佛罗里达州立大学的GEOSET工作室将被用来提高本科生和研究生的专业发展。本科生，特别是女化学家，将通过大学的本科生研究项目招募，并接受科学和演讲技巧方面的指导。在研究小组先前成功的基础上，研究生将合作制作几个信息丰富、有竞争力、编辑精良的关于聚电解质和聚电解质复合物的教育视频。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.