Dissolution Processing of Nanostructured Polymers Tailored for Effective Utilization of Cellulosics

智力优势：该研究提出了一种综合方法来溶解纤维素，这是一种丰富的可再生资源，是将其加工成功能性聚合物、特种化学品和生物燃料的重要步骤。虽然有几种方法已被证明对活化结晶纤维素有用，但寻找能有效溶解纤维素的溶剂仍在进行中。目前已知的几种能够溶解纤维素的溶剂都是在严格且常常相互矛盾的成分和温度条件下进行的，对此还缺乏基本的了解。项目团队提出的研究计划的前提是，对纤维素-溶剂分子相互作用（纳米尺度）的基本了解，加上对半结晶纤维素（微观）颗粒溶解机制的了解，可以导致纤维素生物质溶剂加工条件的合理选择和（宏观）优化。为此，该团队的目标是：(1)推进对分子间相互作用的基本理解，这些相互作用在选择的溶剂系统中似乎有希望溶解纤维素，并以适当的参数表达这些相互作用；(2)确定和量化控制固体纤维素溶解的传输现象和动力学，例如溶剂渗透、从晶体到非晶态的转变、样品膨胀和聚合物链解开。(3)通过模拟多分散纤维素颗粒的溶解（采用1和2中确定的参数），探索溶剂和添加剂混合物的协同作用，以及测试生物质样品的溶解，指导从实验室到工业生产的规模扩大。在上面的研究中，该团队将以naoh为基础的水性和离子液体溶剂系统为目标，这些系统具有过程集成的潜力，并且与纤维素功能化化学和生物催化相兼容。这项研究的一个主要新颖之处在于，该团队齐心协力，从基本的（超）分子水平到实际的、大规模的水平，合理地整合纤维素溶解信息。这将对主要依靠经验的方法产生变革性影响。进一步的新方面包括(i)理解不同溶剂系统中分子相互作用的统一方法，包括测试最近关于疏水效应重要性的假设，这违背了当前的智慧；（ii）基于纤维素膨胀和质量损失的实时监测，结合现象学建模，对溶解机制进行量化；（iii）溶解过程中纤维素生物质结构演化的表征；(4)多分散纤维素颗粒溶解实验及种群平衡模型。这些研究课题中的每一个在文献中都是新的，同时解决所有这些问题应该证明是强有力的。更广泛的影响：总之，这项研究将对利用纤维素作为合成高附加值功能性聚合物和化学品的原料以及生物燃料生产的努力产生积极和及时的影响。该团队的发现将有利于纳米/生物应用，其中需要明确定义的纤维素表面或纳米颗粒，以及纤维素及其衍生物的分析表征；还可以溶剂加工难溶液晶聚合物和碳纳米管。将与工业界和欧洲的研究人员进行合作。该项目将整合研究和教育，将与生物质、溶剂选择和溶解模型相关的讲座和项目纳入pi在本科和研究生阶段教授的各种课程中。一些学生将为这项研究做出贡献，从而产生既受过先进技术训练又对有效利用资源敏感的美国科学家。该团队将与AIChE学生俱乐部合作，开发并提供面向中学生和大一学生的外展活动。

Intellectual Merit: The proposed research addresses the outstanding need for an integrated approach to dissolve cellulosics, an abundant and renewable resource, as an essential step for their processing into functional polymers, specialty chemicals, and biofuels. While several approaches have proven useful for activation of crystalline cellulose, the search is still on for solvents that can effectively dissolve cellulose. The few known solvents that are capable of dissolving cellulose do so under strict and often conflicting composition and temperature conditions, and fundamental understanding is lacking. The project team bases the proposed research program on the premise that fundamental understanding of cellulose-solvent molecular interactions (nanoscale), coupled with knowledge of the dissolution mechanism of semicrystalline cellulosic (microscopic) particles, can lead to the rational selection and (macroscopic) optimization of solvent processing conditions for cellulosic biomass. To this end, the team aims to (1) advance fundamental understanding of intermolecular interactions acting in select solvent systems that appear promising for dissolving cellulose, and express these interactions in terms of appropriate parameters, (2) identify and quantify the transport phenomena and kinetics governing the dissolution of solid cellulose, e.g., solvent penetration, transformation from crystalline to amorphous domains, specimen swelling, and polymer chain untangling, and (3) guide scale-up from the lab to industrial production by modeling the dissolution of polydisperse cellulose particulates (employing parameters determined in 1 and 2), exploring synergisms in mixtures of solvents and additives, and testing the dissolution of biomass specimens. In the above the team will target aqueous NaOH-based and ionic liquid solvent systems that exhibit a potential for process integration and are compatible with cellulose functionalization chemistry and biocatalysis. A main novelty of the proposed research resides in the team's concerted effort to rationally integrate cellulose dissolution information from the fundamental, (supra)molecular level to the practical, large-scale. This would have a transformative effect on what is mostly an empirical approach. Further novel aspects include (i) a unified approach for understanding molecular interactions in different solvent systems, including testing a recent hypothesis on the importance of hydrophobic effects which defies current wisdom; (ii) quantification of the dissolution mechanism, based on real-time monitoring of cellulose swelling and mass loss coupled with phenomenological modeling; (iii) characterization of cellulosic biomass structural evolution during dissolution; and (iv) experiments and population balance modeling on dissolution of polydisperse cellulose particulates. Each of these research topics will be new in the literature, and addressing all in tandem should prove powerful. Broader Impacts: In summary, this research will have a positive and timely impact on efforts directed toward the utilization of cellulosics as starting material for the synthesis of high value-added functional polymers and chemicals and also for biofuel production. The team's findings will be beneficial to nano/bio-applications where well-defined cellulose surfaces or nanoparticles are desired, and for the analytical characterization of cellulose and its derivatives; also to the solvent processing of difficult-to-dissolve liquid crystalline polymers and carbon nanotubes. Collaborations will be pursued with researchers in industry and in Europe. This project will integrate research and education by incorporating lectures and projects related to biomass, solvent selection, and dissolution modeling in the various courses that the PIs teach at both the undergraduate and graduate levels. Several students will contribute to this research, resulting in U.S.-based scientists who have both advanced technical training and sensitivity toward efficient resource utilization. The team will work with the AIChE student club to develop and offer outreach activities geared toward middle-school and 1st year college students.