2001 Technology for a Sustainable Environment: NSF/EPA Partnership for Environmental Research: Design and Optimization of Non-Fluorous CO2-Philic Polymers (TSE01-F)

摘要CTS-012440Beckman，EricU of Pittsburch非氟亲二氧化碳聚合物的设计和优化二氧化碳在化学加工中的应用继续引起人们的极大兴趣，因为二氧化碳通常比传统有机溶剂造成的危害更小。人们一度认为二氧化碳可以简单地取代许多有机溶剂，但后来的研究表明，二氧化碳是一种相当弱的溶剂，因此需要不切实际的高压来溶解感兴趣的化合物。20世纪90年代S发现的“亲二氧化碳”突然使许多应用在技术上成为可能，极大地提高了人们对二氧化碳作为溶剂的兴趣。这些新的亲二氧化碳聚合物，主要是含氟聚合物，允许二氧化碳的许多新应用，从多相聚合到均相催化。尽管氟化两亲化合物在技术上是成功的，但其高昂的成本使该工艺的经济性变得不利，除非能以高于99%的效率回收“亲二氧化碳”。使用氟化前体所固有的缺点极大地阻碍了大多数二氧化碳新应用的商业化，因此基于二氧化碳的技术的全部前景尚未实现。因此，我们对非氟二氧化碳亲和体的设计进行了研究。首先，开发了一套用于设计无氟二氧化碳亲和剂的热力学启发式。聚醚-碳酸酯的设计证明了这些经验法则的适用性，聚醚-碳酸酯是一种在二氧化碳中表现出比全氟聚醚更低的混合压力的聚合物，并且是可生物降解的。这些材料的合成方法很容易产生表面活性剂和其他功能分子，从而为各种工艺经济地使用二氧化碳打开了大门。到目前为止，我们已经使用我们的简单启发式设计了三种类型的非氟亲二氧化碳化合物；我们预计最终会发现其他类型的亲二氧化碳化合物，极大地拓宽了二氧化碳作为溶剂的适用范围。如果我们继续合成和测试所有潜在有用的结构，可能的设计变量(共聚物组成和拓扑结构)的数量将创建一个不切实际的大程序。此外，传统的热力学模型不能预测所有可能排列的行为。因此，我们建议进行一项计划，其最终目标是充分了解组成和拓扑结构对我们的新的亲二氧化碳分子在二氧化碳中的相行为的影响。我们建议结合定向合成、选定热物理性质的测量、高压FT-IR和从第一性原理开发精确的势函数来数学描述我们的材料与二氧化碳混合的热力学。匹兹堡大学的研究将集中于模型材料的合成，相行为的研究，以及描述分子结构对相行为影响的热力学模型的创建。这些任务将与奥本大学(C.R.Roberts)正在进行的研究相协调，在那里将使用高压红外测量来评估二氧化碳与我们模型聚合物中包含的Lewis碱基的特定相互作用的强度。高压红外工作为合成设计和构建二氧化碳-聚合物相互作用的准确势能模型提供了输入。

AbstractCTS-012440Beckman, EricU of PittsburghDesign and Optimization of Non-Fluorous CO2-Philic Polymers The application of CO2 to chemical processing continues to elicit significant interest, as CO2 generally poses fewer hazards than conventional organic solvents. At one time it was thought that CO2 could simply replace many organic solvents, but subsequent work showed that CO2 is a rather feeble solvent, and hence unrealistically high pressures are needed to dissolve compounds of interest. The discovery during the 1990's of "CO2-philes" suddenly rendered a number of applications technically possible, greatly raising interest in CO2 as a solvent. These new CO2-philes, primarily fluoropolymers, allowed a host of new applications for CO2, from heterogeneous polymerization to homogeneous catalysis. Although fluorinated amphiphiles were technically successful, their high cost renders the economics of a process unfavorable unless the "CO2-phile" can be recycled at greater than 99% efficiency. The drawbacks inherent to the use of fluorinated precursors have greatly inhibited the commercialization of most new applications for CO2, and thus the full promise of CO2-based technology has yet to be realized. Consequently, we have investigated the design of non-fluorous CO2-philes. First, a set of thermodynamic heuristics for the design of non-fluorous CO2-philes was developed. The applicability of these rules-of-thumb was demonstrated by the design of poly(ether-carbonates), polymers that exhibit lower miscibility pressures in CO2 than perfluoropolyethers and are biodegradable. The method of synthesis of these materials readily allows generation of surfactants and other functional molecules, opening the economical use of CO2 to a variety of processes. To date, we have used our simple heuristics to design three types of non-fluorous CO2-phile; we expect that others will ultimately be found, greatly broadening the applicability of CO2 as a solvent. The number of possible design variables (copolymer composition and topology) creates an impractically large program if we continue to synthesize and test all potentially useful structures. Further, conventional thermodynamic models are incapable of predicting the behavior of all of the possible permutations. Consequently, we propose to conduct a program whose ultimate aim is to fully understand the effect of composition and topology on the phase behavior of our new CO2-philes in carbon dioxide. We propose to combine targeted synthesis, measurement of selected thermophysical properties, high pressure FT-IR, and development of an accurate potential function from first principles to mathematically describe the thermodynamics of mixing of our materials with CO2. Success will allow us to numerically optimize the structure of non-fluorous CO2-philes.Research at the University of Pittsburgh will focus on the synthesis of model materials, investigation of phase behavior, and creation of a thermodynamic model that describes the effects of molecular structure on phase behavior. These tasks will be coordinated with research underway at Auburn University (C.R. Roberts), where high pressure IR measurements will be employed to evaluate the strength of specific interactions of CO2 with the Lewis base groups incorporated into our model polymers. The high pressure IR work provides input both to the synthetic design and the construction of an accurate potential model for CO2-polymer interactions.