SGER: Supercritical Levitation Polymerization and Processing

在超临界聚合过程中，聚合物链增长到由其在溶剂的主要密度(或压力和温度)条件下的溶解度决定的相对分子质量。链长的进一步增长导致相分离并导致析出。在这个项目中，通过调整溶剂环境的密度使其与形成的聚合物的密度相同，聚合将在等密度条件下进行。这种等密度操作有望通过浮力确保悬浮，并防止相分离聚合物的沉淀。对于超临界溶剂，可以通过控制温度、溶剂组成(如果使用混合物)的压力，以及各种聚合物和聚合体系的等压条件，很容易实现密度调整。这是一种模拟地球上空间过程的微重力环境的方法。该研究项目的目标是通过在与产品聚合物密度完全相同的超临界流体中合成具有精确几何和形态的聚合物材料。这将防止聚合物的沉淀，并允许制造任何所需结构的分子的聚合。这项研究将集中在通过合成聚苯乙烯和在等压超临界流体溶剂中结晶聚乙烯来验证他的假设。他将探索将二氧化碳或丁烷等流体与密度较高的流体(如氙气或六氟化硫)混合使用。

In supercritical polymerization processes, polymer chains grow to molecular weights determined by their solubility under the prevailing density (or pressure and temperature) conditions of the solvent. Further growth in the chain length results in phase separation and leads to precipitation. In this project, polymerizations will be conducted under isopycnic conditions by adjusting the density of the solvent environment to be identical to the density of the polymer formed. This iso- density operation is expected to insure levitation by buoyancy and prevent precipitation of the phase-separated polymer. Density adjustments are readily achievable for supercritical solvents through manipulation of either the pressure of the temperature, of the solvent composition (if mixtures are used), and isopycnic conditions for a variety of polymers and polymerization systems are possible. This is a way to simulate the micro gravity environment of space-based processes on earth. The objective of the research project is to make polymeric materials of precise geometries and morphologies by synthesizing them in a supercritical fluid of precisely the same density as the product polymer. This would prevent precipitation of the polymer and permit polymerization of molecules of any desired structure to be fabricated. The research will focus on testing his hypothesis by synthesizing polystyrene and crystallizing polyethylene in isopycnic supercritical fluid solvents. He will explore using mixtures of fluids such as carbon dioxide or butane with fluids of higher density such as xenon or sulfur hexafloride.