Collaborative Research: Exploring the role of branching in determining the physicochemical properties of dendritic, hyperbranched and linear bis-MPA polyesters

我们周围的材料中有很大一部分是由塑料制成的，也被称为“聚合物”。 绝大多数合成聚合物在分子水平上表现出类似于弦的线性结构。 在过去的几十年中，已经设计并商业化制造了许多具有更树状分子结构的支化聚合物。 从直链到支链的结构差异导致了独特的性能和应用。 杜兰大学的Grayson教授和南密西西比大学的Nazarenko教授正在使用新的合成方法来控制聚酯家族中分支的确切数量。 他们研究聚酯的性质，以更好地了解如何在分子水平上控制聚合物结构，从而产生具有改进行为和性能的聚酯。 这一努力使研究人员从本科和研究生水平在一个多学科的，协作的方法。 该项目还包括推广到当地公立高中化学课，以展示使用科学方法来更好地理解化学中的基本概念。一个新的跨学科考古化学课程也正在开发中。 在化学部大分子、超分子和纳米化学项目的支持下，新的合成工具正在用于制备基于双（羟甲基）丙酸单体的线性、超支化、树枝状和“假树枝状”聚合物库。 传统的（核磁共振）和更新颖的（质谱）表征技术正在被用来阐明这些聚合物的每个架构类的结构以及反应性。 X射线研究结合计算机建模，以确认这些聚酯中发生的分子内和分子间氢键的性质。 进行压力-体积-温度研究，以了解在熔融和固体状态下的分子堆积。 最后，材料的介电性能正在研究中，并与分支类型相关，因为这些材料显示出高介电常数材料的前景。该奖项反映了NSF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。

A significant percentage of the materials around us are made from plastics, also referred to as "polymers". The vast majority of synthetic polymers exhibit a linear structure, resembling a string, on the molecular level. Within the last few decades, a number of branched polymers, with a more tree-like molecular structure, have been designed and made commercially. The difference in structure from linear to branched results in unique properties and applications. Professor Grayson at Tulane University and Professor Nazarenko at the University of Southern Mississippi are using new synthetic methods to control the exact amount of branching in a family of polyesters. They study the properties of the polyesters to better understand how controlling polymer structure on the molecular level can yield polyesters with improved behavior and performance. This effort engages researchers from both the undergraduate and the graduate levels in a multi-disciplinary, collaborative approach. This project also include outreach to local public high school chemistry classes to demonstrate the use of the scientific method to better understand fundamental concepts in chemistry. A new interdisciplinary archeological chemistry course is also under development. With the support from the Macromolecular, Supramolecular and Nanochemistry Program from the Division of Chemistry, new synthetic tools are being employed to prepare a library of linear, hyperbranched, dendritic and "pseudodendritic" polymers based on the bis(hydromethyl)propanoic acid monomer. Both traditional (nuclear magnetic resonance) and more novel (mass spectrometry) characterization techniques are being utilized to elucidate the structure as well as the reactivity of each architectural class of these polymers. X-ray studies are combined with computer modeling to confirm the nature of the intra-and inter-molecular hydrogen bonding that occurs in these polyesters. Pressure-volume-temperature studies are carried out to understand the molecular packing in the melt and solid states. Finally, the materials dielectric properties are being investigated and correlated with the type of branching, as these materials show promise for high dielectric constant materials.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.