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，斯坦福大学的夏岩教授将开发新的化学，以产生新型可降解塑料，以应对持久性塑料对环境和人类健康的重大生命周期挑战。2018年，美国有2700万吨塑料被填埋或排放到环境中，这些塑料是不可降解的。可按需回收、降解或解聚的新型聚合物在环境可持续性以及许多技术和生物医学应用方面都是非常理想的。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意识，并招收和培养大学预科学生，特别是湾区代表不足的学生，为未来的STEM职业生涯做准备。这项研究也为本科生和研究生课程中有机化学、聚合物科学和可持续性的结合提供了完美的范例。环烯烃开环歧化聚合(ROMP)是一种广泛使用的合成可控功能聚合物的方法。长期以来，人们一直认为含有富含电子的烯烃的烯醇醚会使ROMP的催化剂失活，并经常用于冷却聚合。但夏实验室发现了令人惊讶的高效环烯醇醚及其与应变环烯烃的共聚，导致了新型具有不稳定酸主链的可降解聚合物。这项研究项目将首次探索富含电子的杂原子取代的环烯及其共聚的歧化化学，并了解热力学和动力学参数如何影响所产生的可降解/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NSF的法定使命，并通过使用基金会的智力优势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.