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、可塑形和拉伸的材料而变得更好。也就是说，塑料已经产生了一个严重的垃圾问题，大多数塑料在使用一次后就被送到了垃圾填埋场。这些生命终结的结果对我们的星球产生了负面影响，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。在化学学部大分子、超分子和纳米化学项目的资助下，密歇根大学安娜堡分校的安妮·j·麦克尼尔教授正在利用环链平衡来回收聚乙烯，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再循环的方法，在稀释条件下，线性聚合物被定量地转化为大环化合物。当浓度增加时，线性聚合物通过相反的过程再生。在本研究中，开发了一系列化学反应将不同的聚乙烯支架解聚成环状化合物。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。聚乙烯也被改造成含有重要官能团的增值嵌段共聚物。该团队外展工作的主要目标是增加当地社区对塑料生命周期的了解，从石油衍生的和生物来源的单体到它们不同的处置命运。为了实现这一目标，研究小组正在为儿童开发和实施有关塑料生命周期的实践活动。此外，正在为当地儿童博物馆创建一个互动展示。NerdNite和在线出版等网站的实施是为了吸引成年人。该项目使参与的研究生和本科生研究人员在有机和无机化学以及聚合物合成和表征方面获得高度跨学科的培训。培训也为他们在教学和化工行业的职业生涯做准备。该研究小组正在开发用于可逆聚乙烯（PE）环解聚的烷烃复分解。研究活动包括评价聚乙烯环解聚合中烷烃的转化条件，以及阐明不饱和水平对环解聚合速率的影响。研究小组为每个PE支架确定了优化的脱氢催化剂，并生成了可能表现出独特性能的新PE大环。最后，该小组将消费后的PE废物转化为原始质量的PE，并将PE重新用于含有卤素，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，并有可能在科学界和公众中对社会产生重大影响。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。

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.