General Strategies Toward Mechanically Robust Biobased Polymers and Composites

近年来，由于可再生自然资源的可持续聚合物对可持续经济和社会的重要性，它们获得了很大的发展势头。天然聚合物，如纤维素、半纤维素、木质素、淀粉、蛋白质和几丁质，已被用于复合材料、塑料、生物燃料和其他应用。从分子生物量合成聚合物，如植物油、松香酸、萜烯、萜类化合物和呋喃，是一个快速发展的领域。然而，与占主导地位的石化衍生聚合物相比，在商业市场上增加生物基聚合物的成分面临着许多日益严峻的挑战。为了促进可持续发展和国家繁荣，该项目将开发下一代可再生聚合物，通过设计基于天然资源聚合物大分子包裹的总体策略来改善其物理性能，特别是解决涉及各种生物质的劣质机械性能的关键障碍。一个中心目标是了解大分子链包裹如何通过超分子相互作用决定这些材料的热性能和机械性能，并建立结构-性能关系。从自然资源中获取可持续的生物基聚合物正面临着许多严峻的挑战。其中，许多聚合物的机械性能较差，很大程度上是由于其固有的低链缠结（因此具有很高的链缠结分子量）。大分子结构和组成在决定这些特性方面起着至关重要的作用。计划中的研究旨在提供一种经济、稳健和通用的方法来增强生物基聚合物的机械性能。其核心思想是通过超分子相互作用，将体积庞大的生物基聚合物包裹在柔韧且高度纠缠的大分子上。拟议研究的总体目标是同时最大限度地利用生物质，并通过结合最低水平的大分子包裹，使生物基大块聚合物在应力下具有高抗拉强度和理想伸长率。该项目包括通过平行努力开发大分子工程方案：(1)含有大量生物质的聚合物，如脂肪酸、树脂酸、异山梨酯、愈创木酚、蒎烯、杜丽林和葡萄糖；(2)基于木质素和纤维素纳米晶须的生物复合材料。一个重要的目标是了解大分子链包裹如何通过超分子相互作用决定这些材料的热性能和机械性能，并建立明确的结构-性能关系。计划中的研究项目旨在探索潜在的变革概念，通过最大限度地利用具有增强热机械性能的生物基聚合物来解决可持续性问题。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。

NON-TECHNICAL SUMMARYSustainable polymers from renewable natural resources have gained much momentum in recent years given their importance to a sustainable economy and society. Natural polymers, such as cellulose, hemicellulose, lignin, starch, proteins, and chitin, have been utilized in composites, plastics, biofuels and other applications. The development of synthetic polymers from molecular biomass, such as plant oils, rosin acids, terpenes, terpenoids, and furan, is a fast-growing area. However, there are many mounting challenges in increasing the component of biobased polymers in the commercial market, in contrast with dominant petrochemical-derived counterparts. To promote sustainability and national prosperity, this project will develop next-generation renewable polymers by designing general strategies based on wrapping of macromolecules on polymers from natural resources to improve their physical properties, especially addressing critical hurdles on inferior mechanical properties involving a variety of biomass. A central goal is to understand how macromolecular chain wrapping via supramolecular interactions dictates thermal and mechanical properties of these materials and to establish structure-property relationships.TECHNICAL SUMMARYSustainable biobased polymers from natural resources are facing a lot of compelling challenges. Among them, many polymers suffer inferior mechanical properties, largely due to their inherent low chain entanglements (thus, they have very high chain-entanglement molecular weight). Macromolecular architectures and compositions play vital roles in dictating these properties. The planned research is aimed to provide an economical, robust, and general approach to enhance mechanical properties of biobased polymers. The central idea is to wrap bulky biobased polymers with a flexible and highly entangled macromolecule via supramolecular interactions. The overall goal of the proposed research is to simultaneously maximize the use of biomass and enable biobased bulky polymers with high tensile strength and desirable elongation under stress by incorporating minimal levels of macromolecular wrapping. This project includes the development of macromolecular engineering protocols through parallel efforts on: (1) polymers containing bulky biomass such as fatty acid, resin acid, isosorbide, guaiacol, pinene, tulipalin, and glucose; and (2) biocomposites based on lignin and cellulose nanowhiskers. An essential goal is to understand how macromolecular chain wrapping via supramolecular interactions dictates thermal and mechanical properties of these materials and to establish clear structure-property relationships. The planned research program seeks to explore potentially transformative concepts to address sustainability issues by maximizing the use of biobased polymers with enhanced thermomechanical properties.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.