Collaborative Project: GOALI: Acrylic Resins Product and Process Design through Combined Use of Quantum Chemical Calculations and Spectroscopic Methods

摘要1160169/1159736索罗斯/她的智慧功绩。在我们最近成功的目标工作中，在没有任何常规热引发剂的情况下，我们在理解丙烯酸酯的自发热聚合方面取得了重大进展。通过结合有效的第一性原理量子力学密度泛函理论(DFT)计算和聚合物样品的光谱测量，我们最终确定了单体自引发和链转移反应的机理，包括反应中间体和过渡态。我们还计算了气相反应的速率常数(频率因子和活化能)。现在，在这些结果的基础上，我们建议通过协调和协作的实验和理论/计算研究来改进对烷基丙烯酸酯热自发聚合(不添加常规热引发剂)的实验控制。为了加深我们的理论理解，将使用越来越现实的溶剂模型进行计算，包括量子区域中的多个显式溶剂分子和最近开发的van der Waals DFT泛函，以改善分子间势能面。同时，将根据计算结果设计间歇反应器聚合实验，以评估溶剂类型、单体和溶剂浓度以及温度对聚合物链微结构特征和聚合速率的影响。本项目的具体目标是：(A)我们将开发一种计算高效的方法来计算单体自引发、单体和溶剂共引发以及链转移等自发热丙烯酸酯聚合反应的可靠的液相速率常数。(B)我们将设计和进行间歇聚合实验，并利用光谱方法测量所产生的高分子链的微观结构特征，以验证和完善我们的理论预测。(C)利用开发的计算方法和间歇聚合实验，我们将研究各种溶剂和含酮官能团的单体的结构-反应性关系。(D)我们将使用这些理论和实验理解来指导我们对新型热引发剂(允许快速但可控的丙烯酸酯热聚合的溶剂)的计算筛选和实验验证。我们的最终目标是设计高性能的丙烯酸树脂和化学自控聚合工艺，以具有吸引力的总体成本生产丙烯酸树脂。该项目的潜在影响包括社会(通过提高安全性)、环境、经济和人力资源开发等。自发热聚合允许以较低的运营成本生产更高质量、更环保的溶剂型涂料和涂料。低分子量聚合物和低聚物溶液具有足够低的粘度--即使在高固体含量时也是如此--因此需要较少的可喷雾和可刷洗的溶剂。减少或消除热引发剂(例如，氮腈或有机过氧化物，通常是树脂配方中最昂贵的成分)和提高反应速度都降低了操作成本。由于热引发剂在最终产品中消除了残留基团(这会对聚合物性能产生不利影响，如抗紫外线辐射)，并在聚合反应器的最佳控制中使用了定量了解，从而提高了树脂质量。PIS和Co-PI将培训和指导两名博士研究助理以及六名本科生，他们将参与从量子水平计算和超级计算到实验室实验和光谱方法的广泛研究活动。项目成果将在会议上以及期刊和会议记录文件中向公众公布。与我们过去的研究活动一样，我们将在这个项目中挑选、培训和指导代表人数不足的群体的学生。

Abstract1160169/1159736Soroush / RappeIntellectual Merit. In our recent successful GOALI work, we have made significant advances in understanding the spontaneous thermal polymerization of acrylates in the absence of any conventional thermal initiators. By combining efficient first-principles quantum-mechanical density functional theory (DFT) calculations with spectroscopic measurements of polymer samples, we have identified conclusively the mechanisms for monomer self-initiation and chain transfer reactions, including the reaction intermediates and transition states. We also calculated rate constants (frequency factors and activation energies) for the reactions in the gas phase.Now, building on these results, we propose to improve experimental control of the thermal spontaneous (without addition of conventional thermal initiators) polymerization of alkyl acrylates through coordinated and collaborative experimental and theoretical/computational research. To deepen our theoretical understanding, calculations will be performed with increasingly realistic solvent models, including multiple explicit solvent molecules in the quantum region and recently-developed van der Waals DFT functionals, to improve intermolecular potential energy surfaces. Concurrently, batch reactor polymerization experiments will be designed on the basis of the computational results and conducted to evaluate the influence of solvent type, monomer and solvent concentrations, and temperature on polymer-chain microstructural characteristics and polymerization rate.The specific goals of this project are: (a) We will develop a computationally efficient method of calculating reliable liquid-phase rate constants for spontaneous thermal acrylate polymerization reactions such as monomer self-initiation, co-initiation by monomer and solvent, and chain transfer. (b) We will design and conduct batch polymerization experiments and, using spectroscopic methods, measure the microstructural characteristics of the produced polymer chains to validate and refine our theoretical predictions. (c) Using the developed computational method and batch polymerization experiments, we will study the structure-reactivity relationship for various solvents and monomers with a ketone functional group. (d) We will use these theoretical and experimental understandings to guide our computational screening and experimental validation of novel thermal initiators (solvents that permit rapid but controllable thermal polymerization of acrylates). Our ultimate goal is to design high-performance acrylic resins and chemically self-regulated polymerization processes for the production of acrylic resins at attractive overall cost.Broader Impacts. The potential impacts of this project are societal (through improved safety), environmental, economic, and in human resource development, among others. Spontaneous thermal polymerization allows for the production of higher quality, environmentally friendlier solvent-borne paints and coatings at lower operating costs. Low molecular weight polymer and oligomer solutions have adequately low viscosity?even at high weight percent solids?thus requiring less solvent to be sprayable and brushable. The reduction or elimination of thermal initiators (e. g. azonitrile or organic peroxides, normally the most expensive component of a resin formula) and the increase of reaction rate both lower the operating costs. The elimination of residual groups due to the thermal initiators in the final product (which adversely affect polymer properties such as resistance to UV radiation) and the use of the quantitative understanding in optimal control of the polymerization reactors improve the resin quality. The PIs and Co-PI will train and mentor two doctoral research assistants as well as six undergraduate (REU) students, who will participate in broad range of research activities from quantum-level computations and supercomputing to laboratory experiments and spectroscopic methods. The project results will be released to the public at conferences and in journal and conference proceedings papers. As in our past research activities, students from under-represented groups will be selected, trained and mentored in this project.