Controlled Fragmentation of Polyolefinic Materials triggered by Microwave Irradiation

该项目旨在开发一种新的策略，将一大类传统热塑性塑料转化为适合进一步再利用、再循环和升级回收的材料。设计既保留传统热塑性塑料的性能，又能在使用寿命结束时可控地分解成可重复使用的聚合物链碎片的材料将成为目标。这种热分解过程产生的聚合物链碎片将用于合成可回收的聚酯，这反过来又有望为循环经济做出贡献，这是一种减少浪费和避免过度使用资源的经济体系。聚合物合成、材料制造和多尺度建模将集成在这个项目中。该项目有望为热塑性材料的有效设计建立指导方针；制造这些材料的能力可能会为可回收部件在家庭、建筑、汽车和美国经济其他部门的大规模应用开辟一个新的方向。该项目将为研究生、本科生和当地高中生提供充足的研究和教育机会。参与该项目的学生将获得基本概念的知识，并了解当前材料科学和可持续性面临的挑战。这个多学科项目旨在激发本科生和K-12学生的兴趣，并通过获得最先进的聚合物回收/升级回收技术的知识，提高公众对STEM领域的认识。重点将放在积极招收背景未被充分代表的学生。研究的一些成果和相关的教育材料将通过科学和工程门户nanoHUB提供给广泛的科学界，nanoHUB是计算纳米技术网络的一部分。该研究计划的目标是开发一种制造策略，使微波触发的聚烯烃材料在其使用寿命结束后的化学升级回收成为可能。聚烯烃材料（POMs）具有常规聚烯烃的性能，但能够控制分解成分子量分布明确的大分子链片段，将是设计的目标。分散在聚甲醛中的功能化纳米片在短微波脉冲的作用下会局部加热并引发碎片。大分子链片段将进一步用于合成可回收的半晶聚酯（rpe）。此外，这些半结晶聚酯的循环解聚和再聚合将被证明。实验研究和计算模型将迭代整合。一个多尺度模型集成粗粒度（节能耗散粒子动力学）和连续方法将被开发。模型参数将基于实验数据，模型预测将通过实验验证。建模预测将用于了解和优化裂解过程和RPE合成和解聚，以实现链片段的目标分子量分布，并优化可回收半晶聚酯的解聚和再聚收率。设计的聚烯烃微波触发破碎功能将在制造过程中内置，而不会影响材料的机械性能。提出的研究直接解决了当前的挑战，重点是开发高效的化学工艺，提高环境可持续性，设计量身定制的材料，以及开发辅助复合材料合成和加工的计算机模拟方法。本文开发的多尺度建模框架将考虑所有物质的反应、传热和扩散，包括链片段、自由基和低分子量试剂。该模型与实验验证相结合，将使人们对受控破碎和随后的解聚/再聚合周期中发生的动态过程有一个基本的了解。预计该计划的实现将对按需解构热塑性塑料的发展产生变革性影响，并具有当前使用材料的性能和可加工性。从塑料废物中生产的聚烯烃材料有望成为循环经济的重要组成部分。本科生和研究生将接受模型和代码开发以及材料合成、制造和表征方面的培训。重要的是，专注于材料建模的学生和进行实验的学生将在这个项目中密切互动，这样所有参与的学生都将获得宝贵的合作经验，并对他们的项目有更广阔的视野。重点将放在支持学生的多样性。此外，该项目有望激发本科生和K-12学生对STEM领域的兴趣。选定的研究成果将纳入两所pi的课程；相关的教育材料将通过nanoHUB门户网站提供。该项目是由过程系统、反应工程和分子热力学计划的ENG/CBET和建立计划，以刺激竞争研究（EPSCoR）共同资助的。该奖项反映了NSF的法定使命，并被认为是值得支持的，通过评估使用基金会的智力价值和更广泛的影响审查标准。

This project seeks to develop a novel strategy to convert a large class of conventional thermoplastics into materials suitable for further reuse, recycling, and upcycling. The design of materials that retain properties of conventional thermoplastics but are capable of end-of-life controlled deconstruction into reusable polymer chain fragments will be targeted. The polymer chain fragments produced by this thermal decomposition process will be used to synthesize recyclable polyesters, which in turn are expected to contribute to a circular economy, an economic system that reduces waste and avoids excessive use of resources. Polymer synthesis, materials fabrication, and multiscale modeling will be integrated in this project. The project is expected to establish guidelines for efficient design of thermoplastic materials; the ability to manufacture these materials could potentially open a novel direction in large-scale applications of recyclable components employed in the household, construction, automotive, and other sectors of the U.S. economy. The project will offer ample research and educational opportunities for graduate, undergraduate, and local high school students. Students working on this project will gain knowledge of fundamental concepts and an understanding of current challenges in materials science and sustainability. This multidisciplinary project is expected to stimulate the undergraduate and K-12 students’ interest and increase public awareness in STEM fields via gaining knowledge of the state-of-the-art polymer recycling/upcycling technologies. A strong emphasis will be placed on actively recruiting students with underrepresented backgrounds. Some of the outcomes of the research and relevant educational materials will be made available to the broad scientific community via a science and engineering gateway, nanoHUB, which is a part of the Network for Computational Nanotechnology.The objective of this research program is to develop a manufacturing strategy that enables microwave-triggered chemical upcycling of polyolefinic materials after their end-of-life. The design of polyolefinic materials (POMs) with properties of conventional polyolefins but capable of controlled deconstruction into macromolecular chain fragments with well-defined molecular weight distribution will be targeted. Functionalized nanosheets dispersed within the POMs will localize heating and trigger fragmentation upon application of short microwave pulses. Macromolecular chain fragments will be further used to synthesize recyclable semicrystalline polyesters (RPEs). Furthermore, cyclic depolymerization and repolymerization of these semicrystalline polyesters will be demonstrated. Experimental studies and computational modeling will be iteratively integrated. A multiscale model integrating coarse-grained (energy-conserving dissipative particle dynamics) and continuum approaches will be developed. Model parameters will be based on the experimental data, and model predictions will be validated with experiments. Modeling predictions will be used to understand and optimize the fragmentation process and RPE synthesis and depolymerization to achieve a targeted molecular weight distribution of chain fragments and to optimize depolymerization and repolymerization yield for the recyclable semicrystalline polyesters. The designed polyolefinic microwave-triggered fragmentation functionality will be built-in during fabrication without compromising the mechanical properties of the materials. The proposed research directly addresses current challenges by focusing on developing efficient chemical processes, improving environmental sustainability, designing tailor-made materials, and developing computer simulation approaches aiding composite material synthesis and processing. The multiscale modeling framework developed herein will account for the reactions, heat transfer, and diffusion of all the species including chain fragments, macroradicals, and low molecular weight reagents. This model, in conjunction with experimental validation, will allow one to gain a fundamental understanding of the dynamic processes taking place during controlled fragmentation and subsequent depolymerization/repolymerization cycles. The realization of the proposed program is anticipated to have a transformative impact on development of deconstructable-on-demand thermoplastics, with properties and processability of currently employed materials. Polyolefinic materials produced from plastic waste are envisioned to become an essential part of the circular economy. Undergraduate and graduate students will be trained in model and code development and in materials synthesis, fabrication, and characterization. Importantly, the students focusing on materials modeling and the students conducting experiments will interact closely within this project, so that all the students involved will gain a valuable collaborative experience and a broader perspective on their projects. A strong emphasis will be placed on supporting student diversity. Further, this project is expected to stimulate undergraduate and K-12 students’ interest in STEM fields. Selected research outcomes will be incorporated into courses taught by both PIs; related educational materials will be made available via the nanoHUB portal.This project is jointly funded by the Process Systems, Reaction Engineering, and Molecular Thermodynamics Program of ENG/CBET and the Established Program to Stimulate Competitive Research (EPSCoR),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.