Collaborative Research: Fundamental Basis for General Molecular Weight Determination for Ionic Polymers

该奖项由宾夕法尼亚州立大学的Ralph H. Colby博士和弗吉尼亚理工学院和州立大学的Louis A. Madsen博士共同资助，大分子、超分子和纳米化学项目获得了化学学部化学测量和成像项目的部分资助。该团队正在开发新的方法来测量带有离子的聚合物的分子量。聚合物是由许多重复单元组成的长链分子，它们通过碳-碳键连接在一起。虽然有许多可靠的技术用于精确测定非离子（不带电）聚合物的分子量，但将这些方法应用于离子聚合物通常是困难的。离子聚合物是一类非常重要的聚合物，在工业上用作水性油漆和涂料的增稠剂以及水净化技术。很大一部分生物分子，包括DNA、RNA、许多多肽和多糖，也是重要的离子聚合物的例子。该项目开发了一套新的强大的技术来确定天然和合成离子聚合物的分子量。这些新方法的发展通过加速离子传导能源材料和生物可降解材料的发展，使社会受益。这样的研究活动训练学生在高分子（塑料）工业的未来就业大分子科学。材料和劳动力的发展是保持美国工业全球竞争力的核心。本研究的重点是开发四种方法，利用易于测量的半稀释无纠缠离子聚合物溶液的动态特性来获得数平均分子量。每种方法都依赖于校准测量的特定组合，因此每种方法都直接确定溶液中链的数量密度，从而确定溶液中聚合物的数平均分子量。这四种方法的优点是它们对盐浓度不敏感（因为盐可能具有挑战性甚至不可能去除），并且具有转化潜力，可以在使用很少样品的情况下实现离子聚合物的常规分子量测定。预计这些方法将迅速采用，从而使聚电解质和离聚物的发展迅速增长，以适应各种应用。本项目中理论和实验方法的发展和验证进一步影响了聚合物科学的物理基础，并使人们对离子聚合物的性质有了新的认识。虽然主要是使用合成聚合物进行测试和开发，但这项研究也有望实现生物聚合物（如透明质酸、肝素、DNA和RNA）分子量的常规表征。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。

With this award, the Macromolecular, Supramolecular and Nanochemistry Program with partial co-funding from the Chemical Measurement and Imaging Program in the Division of Chemistry is funding Dr. Ralph H. Colby from Pennsylvania State University and Dr. Louis A. Madsen from Virginia Polytechnic Institute and State University. The team is developing new methods for measuring the molecular weight of polymers that have attached ions. Polymers are long-chain molecules consisting of many repeating units that are linked together through carbon-carbon bonds. While there are many firmly established techniques used to accurately determine the molecular weight of nonionic (uncharged) polymers, applying such methods to ionic polymers is usually difficult. Ionic polymers are a very important class of polymers used by industry as thickeners in water-based paints and coatings and in water purification technologies. A large fraction of biological molecules, including DNA, RNA, many polypeptides and polysaccharides are also examples of important ionic polymers. This project develops a novel set of robust techniques that determine molecular weights for both natural and synthetic ionic polymers. Development of these new methodologies benefits society by accelerating the development of ion-conducting energy materials and biodegradable materials. Such research activities train students in macromolecular sciences for future employment in polymer (plastics) industries. The development of both materials and workforce are central to keeping US industries globally competitive.This research is focused on developing four methods that utilize easily measured dynamic properties of semidilute unentangled solutions of ionic polymers to obtain the number-average molecular weight. Each method relies on specific combinations of calibrated measurements so that each one directly determines the number density of chains in solution and thus the number-average molecular weight of the polymers in that solution. These four methods each have the advantage that they are insensitive to salt concentration (since salt can be challenging or even impossible to remove) and have the transformative potential to enable routine molecular weight determinations for ionic polymers, while using very little sample. Quick adoption of these methods is anticipated, allowing rapid growth of the development of polyelectrolytes and ionomers to suit a myriad of applications. Development and validation of the theory and experimental methods in this project further impact the physical underpinnings of polymer science and enable new understanding of ionic polymer properties. While mainly being tested and developed using synthetic polymers, this research also promises to enable routine characterization of molecular weight for biopolymers such as hyaluronic acid, heparin, DNA and RNA.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.