EAGER: CAS: From polymer mixtures to sustainable foams with controlled hierarchical porosity and mechanics

塑料在社会中发挥着至关重要的作用，但它们对环境的影响，从石油为基础的采购到报废处理，引起了重大关注。特别是泡沫塑料的应用，由于其不可再生和有毒的构建块，以及聚合物泡沫的不可回收性和不可降解性而面临挑战。目前的可持续泡沫方法包括重新组装从生物质中提取的有用的聚合物构建块。然而，这些方法会导致浪费并受到可伸缩性限制。该项目引入了一种新颖的、潜在的革命性概念，即直接从未经加工的可再生原料中获得的聚合物混合物中合成泡沫，从而消除了提取的需要。通过研究聚合物的相互作用和发泡机理，可以实现对结构和性能的精确控制。如果成功，该项目将生产出与石油衍生泡沫具有相似加工性和机械性能的泡沫，同时还具有可降解性和可回收性的优势，从而推动真正可持续发展的聚合物泡沫的发展。所获得的知识将扩展到具有类似分子特征的其他聚合物混合物，将影响扩展到生物质基聚合物混合物之外。研究结果和方法将纳入材料加工和聚合物科学课程，以及公共宣传活动。该项目将培养学生可持续聚合物科学/工程原理，培养和教育具有环保意识的材料专业人员。在泡沫塑料应用的背景下，实现对传统聚合物（如聚氨酯和聚苯乙烯）的分子组成和层次结构的精确控制，在其在各个行业的广泛应用中起着关键作用。然而，这些广泛使用的聚合物来源于不可再生和有毒的单体，并且产生不可回收和不可降解的泡沫，这是一个重大的挑战。可持续的替代品包括从生物质衍生的小分子中合成单体或从生物质中提取聚合物并将其重新组装成泡沫。然而，这些方法需要提取过程，导致废物产生和可扩展性限制，而且它们不一定能产生可降解或可回收的泡沫。为了克服这些挑战，该项目提出了一种新的方法，消除了提取过程的需要，而是利用可再生原料中固有的聚合物混合物。目标是直接从未加工的生物质中发现的聚合物混合物中制备具有可控结构和机械性能的分层聚合物泡沫。中心假设是，通过利用电荷络合和热机械加工，可以实现对泡沫的层次结构，孔隙率和机械性能的精确控制。丰富的藻类生物量将被用作可再生聚合物原料来验证这一方法。分析将包括评估泡沫结构、孔隙度、孔隙形态和力学性能，以建立结构-性能关系。此外，还将对土壤的可回收性和退化进行研究。这项研究的成果将推进可持续泡沫制造工艺，使可再生聚合物生产高性能、可降解和可回收的泡沫成为可能。所获得的知识将扩展到生物质基聚合物之外，有助于更广泛地了解具有类似分子特征的其他聚合物混合物。此外，该提案中调查的材料将整合到教学，教育和推广活动中。该奖项反映了美国国家科学基金会的法定使命，并通过基金会的智力价值和更广泛的影响审查标准进行评估，认为值得支持。

NON-TECHNICAL SUMMARYPlastics play a crucial role in society, but their environmental impacts, from petroleum-based sourcing to end-of-life disposal, raise significant concerns. Foam applications, in particular, present challenges due to non-renewable and toxic building blocks, as well as non-recyclability, and non-degradability of the resulting polymer foams. Current sustainable foam approaches involve reassembling useful polymer building blocks extracted from biomass. Yet, these approaches lead to waste and suffer from scalability limitations. This project introduces the novel and potentially transformative concept of synthesizing foams directly from polymer mixtures obtained from unprocessed renewable feedstocks, thus eliminating the need for extraction. By studying polymer interactions and foaming mechanisms, precise control over structure and properties can be achieved. If successful, this project will produce foams that exhibit similar processability and mechanical properties as petroleum-derived counterparts, while also offering the advantages of degradability and recyclability, pushing the boundaries of truly sustainable polymer foams. The knowledge gained will extend to other polymer mixtures with similar molecular features, expanding the impacts beyond biomass-based polymer mixtures. The findings and methodologies will be integrated into materials processing and polymer science curricula, as well as public outreach activities. The project will train students in sustainable polymer science/engineering principles, fostering and educating environmentally conscious materials professionals. TECHNICAL SUMMARYIn the context of foam applications, achieving precise control over the molecular composition and hierarchical structure in conventional polymers, such as polyurethanes and polystyrenes, has played a pivotal role in their widespread utilization across various industries. However, a significant challenge arises from the fact that these widely used polymers are derived from non-renewable and toxic monomers, and result in foams that are non-recyclable and non-degradable. Sustainable alternatives involve synthesizing monomers from biomass-derived small molecules or extracting polymers from biomass and reassembling them into foams. However, these approaches necessitate extraction processes, leading to waste generation and scalability limitations, and they don’t necessarily lead to degradable or recyclable foams. To overcome these challenges, this project presents a novel approach that eliminates the need for extraction processes and instead utilizes the inherent polymer mixtures present in renewable feedstocks. The objective is to prepare hierarchical polymeric foams with controlled structure and mechanical properties directly from polymer mixtures found in unprocessed biomass. The central hypothesis is that by harnessing charge complexation and thermomechanical processing, precise control over the hierarchical structure, porosity, and mechanical properties of the foams can be achieved. Abundant algal biomass will be used as a renewable polymer feedstock to validate this approach. The analysis will encompass evaluating foam structure, porosity, pore morphology, and mechanical properties, to establish structure-property relationships. Additionally, studies will be conducted on recyclability and degradation in soil. The outcomes of this research will advance sustainable foam manufacturing processes, enabling the production of high-performance, degradable, and recyclable foams from renewable polymers. The knowledge gained will extend beyond biomass-based polymers, contributing to a broader understanding of other polymer mixtures with similar molecular characteristics. Furthermore, the materials investigated in this proposal will be integrated into teaching, education, and outreach activities..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.