SGER: Supercritical Levitation Polymerization and Processing

在超临界聚合过程中，聚合物链的分子量取决于它们在溶剂的普遍密度（或压力和温度）条件下的溶解度。链长的进一步增长导致相分离并导致析出。在本项目中，聚合将在等异条件下进行，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。这种等密度操作可以保证浮力的悬浮，防止相分离聚合物的沉淀。通过控制温度压力、溶剂组成（如果使用混合物）以及各种聚合物和聚合体系的等异条件，可以很容易地实现超临界溶剂的密度调整。这是一种在地球上模拟太空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形状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聚合。研究将集中在通过合成聚苯乙烯和在等重超临界流体溶剂中结晶聚乙烯来验证他的假设。他将探索使用二氧化碳或丁烷等流体与氙或六氟化硫等密度更高的流体的混合物。

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.