Diverse Degradable Polymers from Versatile Ring-Opening Metathesis (Co)Polymerization of Electron-Rich Cyclic Olefins

在化学系大分子、超分子和纳米化学项目的支持下，斯坦福大学夏燕教授将开发新的化学方法来生产新型可降解塑料，以解决持久性塑料对环境和人类健康的巨大挑战。2018年，美国有2700万吨不可降解的塑料被填埋或排放到环境中。战略性地设计为可回收、降解或按需解聚的新型聚合物对于环境可持续性以及许多技术和生物医学应用都是非常可取的。该项目整合了多个层面的教育努力，以提高公众对塑料污染和回收的认识，并招募和培养大学预科学生，特别是湾区代表性不足的学生，为未来的STEM职业做好准备。这项研究也为有机化学、聚合物科学和可持续性在本科和研究生课程中的结合提供了完美的例子。环烯烃开环复分解聚合（ROMP）是一种广泛应用的合成可控功能聚合物的方法。具有富电子烯烃的烯醚一直被认为会使ROMP催化剂失活，通常用于抑制聚合。但是夏实验室发现了环烯醚的高效ROMP及其与张力环烯烃的共聚，从而产生了具有酸不稳定骨架的新型可降解聚合物。本研究项目将首次探索富电子杂原子取代环烯烃及其共聚的复分解化学，并了解热力学和动力学参数如何影响所得到的可降解/可解聚聚合物的控制、微观结构、降解特征和物理性质。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 the support of the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry, Professor Yan Xia of Stanford University will develop new chemistry for generating new types of degradable plastics to address the grand end-of-life challenge of persistent plastics to the environment and human health. In 2018, 27 million tons of plastics were landfilled or released into the environment in the US and are nondegradable. New polymers that are strategically designed to be recycled, degraded, or depolymerized on demand are highly desirable for environmental sustainability as well as many technological and biomedical applications. This project integrates educational endeavors at several levels to raise the public awareness of plastic pollution and recycling, and recruit and cultivate pre-college students, especially underrepresented students in the Bay Area, for future STEM careers. The research also provides perfect examples to interface organic chemistry, polymer science, and sustainability in undergraduate and graduate curriculum.Ring-opening metathesis polymerization (ROMP) of cyclic alkenes is a widely used method to synthesize controlled functional polymers. Enol ethers with an electron-rich alkene have long been believed to deactivate the catalysts for ROMP and routinely used to quench the polymerization. But the Xia laboratory discovered surprisingly efficient ROMP of cyclic enol ethers and their copolymerization with strained cyclic alkenes, leading to new types of degradable polymers with acid labile backbones. This research project will explore the metathesis chemistry of electron-rich heteroatom-substituted cyclic alkenes and their copolymerization for the first time, and understand how the thermodynamic and kinetic parameters impact the control, microstructures, degradation profiles, and physical properties of the resulting degradable/depolymerizable polymers.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.