CAS: Repurposing Polyethylene Waste Using Ring-Chain Equilibria

塑料已经改变了我们的生活，主要是通过提供重量轻，耐用的材料，可以成型和拉伸。 也就是说，塑料产生了严重的废物问题，大多数塑料在使用一次后就被送到垃圾填埋场。这些生命终结的结果对我们的地球产生了负面影响，是不可持续的。因此，迫切需要开发新的方法来再利用塑料废物。密歇根大学安阿伯的Anne J. McNeil教授在化学系大分子、超分子和纳米化学项目的资助下，利用环链平衡回收聚乙烯，这是世界上生产最广泛的塑料之一。环-链平衡是一种聚合物回收方法，其中在稀释条件下，线性聚合物定量转化为大环化合物。当浓度增加时，线性聚合物通过相反过程再生。本研究利用一系列化学反应将不同聚乙烯支架材料脱嵌成环状化合物。所开发的方法用于将消费后的聚乙烯废物转化为原始质量的聚乙烯。聚乙烯还被重新利用为含有重要功能化学基团的增值嵌段共聚物。该团队外联工作的主要目标是增加当地社区对塑料生命周期的了解，从石油衍生和生物来源的单体到它们不同的处置后命运。为了实现这一目标，研究团队正在为儿童开发和实施塑料生命周期的实践活动。此外，正在为当地儿童博物馆制作一个互动展览。诸如NerdNite和在线出版等场所都是为了接触成年人而实施的。该项目使参与的研究生和本科生研究人员能够获得有机和无机化学以及聚合物合成和表征方面的高度跨学科培训。培训还为他们在教学和化学工业的职业生涯做好准备。该研究小组正在开发用于聚乙烯（PE）可逆环解聚的烷烃复分解。研究活动包括评估PE环解聚中的烷烃复分解条件，以及阐明不饱和度水平对环解聚速率的影响。 该研究小组为每个PE支架确定了优化的脱氢催化剂，并产生了可能具有独特性能的新PE大环。 最后，该集团将消费后的PE废物转化为原始质量的PE，并将PE再利用为含有卤素，极性或烷基官能团的增值嵌段共聚物。这项工作解决了聚烯烃可回收性的巨大挑战，并有可能对科学界和公众产生重大影响。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。

Plastics have transformed our lives, largely for the better by providing light-weight, durable materials that can be shaped and stretched. This said, plastics have generated a significant waste problem, with most plastics sent to the landfill after only one use. These end-of-life outcomes negatively impact our planet and are unsustainable. As such, there is an urgent need to develop new methods to reuse plastic waste. With funding from the Macromolecular, Supramolecular, and Nanochemistry Program of the Chemistry Division, Professor Anne J. McNeil of University of Michigan Ann Arbor is utilizing ring-chain equilibria to recycle polyethylene, which is one of the most widely produced plastics in the world. Ring-chain equilibria is a method for polymer recycling in which, under dilute conditions, linear polymers are quantitatively transformed into macrocyclic compounds. When the concentration is increased, linear polymers are regenerated via the reverse process. In this research, a series of chemical reactions are developed to depolymerize different polyethylene scaffolds into cyclic compounds. The developed methodology is utilized to convert post-consumer polyethylene waste into virgin-quality polyethylene. Polyethylene is also repurposed into value-added block copolymers containing important functional chemical groups. The primary goal of the team's outreach efforts is to increase the local community's understanding of the lifecycle of plastics, ranging from petroleum-derived and bio-sourced monomers through their different post-disposal fates. To accomplish this goal, the research team is developing and implementing hands-on activities for children on the plastics lifecycle. In addition, an interactive display for a local children’s museum is being created. Venues such as NerdNite and online publishing are implemented to reach adults. This project enables the participating graduate and undergraduate researchers to gain highly interdisciplinary training in organic and inorganic chemistry, as well as polymer synthesis and characterization. The training also prepares them for careers in teaching and in the chemical industries. The research team is developing alkane metathesis for reversible cyclodepolymerization of polyethylene (PE). Research activities include the evaluating of alkane metathesis conditions in the cyclodepolymerization of PE, and the elucidation of the impact of unsaturation levels on cyclodepolymerization rates. The research group identifies optimized dehydrogenation catalysts for each PE scaffold and generates new PE macrocycles that may exhibit unique properties. Finally, the group convert post-consumer PE waste into virgin-quality PE, and repurposes PE into value-added block copolymers containing halogen, polar, or alkyl functional groups. This work tackles the grand challenge of polyolefin recyclability and has the potential to have a significant impact on society, both within the scientific community and in the general public.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.