Modification of Poly (2,6-dimethylphenylene Oxide) as Membrane Materials for Gas-Separation

在追求高渗透、高渗透选择性的二氧化碳/碳氢化合物分离膜材料的过程中，有人建议进行实验研究，以调查一个被忽视的问题。改性聚1，6-二甲基苯醚(PPO)是一种很有前途的二氧化碳和碳氢化合物分离材料。最近，这个研究小组发现，用溴原子取代PPO重复单元中的3和5位可以增加聚合物对二氧化碳的渗透性，同时保持二氧化碳/甲烷的渗透选择性。进一步发现，与其他玻璃态聚合物相比，改性聚合物的扩散率相关的选择性仍然惊人地高，这与传统观点形成鲜明对比，即降低链间堆积将导致聚合物的筛分能力下降。结果表明，芳基溴化PPO具有较低的二氧化碳/甲烷渗透选择性实际上是由于其与溶解度相关的选择性很低所致。假设在聚合物重复单元中引入碱性基团将提高二氧化碳相对于甲烷在聚合物中的溶解度。同时，如果聚合物链段的堆积密度和扭转迁移率也降低(例如通过溴)，得到的聚合物将表现出对二氧化碳的高渗透性和对二氧化碳对甲烷的高渗透选择性。本项目对上述假设进行了系统的实验研究。不同芳基溴化程度的PPO聚合物，将研究芳基胺化和芳基邻苯二甲酰亚胺甲基化，以便涵盖广泛的填充密度和碱性基团的浓度。膜分离技术将是未来十年最重要的发展技术之一。该领域的技术领先地位也将转化为所有化学加工行业制造效率的提高。如果上述假设被证明是正确的，该项目将构成膜科学的重大进步，这将转化为气体混合物膜分离的重大技术进步。

Experimental research is proposed to investigate an overlooked issue in the pursuit of high-permeability, high- permselectivity membrane materials for carbon dioxide/hydrocarbon separations. Modified poly(1,6-dimethyl phenylene oxide) (PPO) is a promising material for the separation of carbon dioxide from hydrocarbons. More recently this research group discovered that substitution at the 3 and 5 positions in the repeat unit of PPO with bromine atoms increases the polymer's permeability to carbon dioxide while retaining the carbon dioxide/methane permselectivity. It was further found that the diffusivity-related selectivity of the modified polymer remains surprisingly high when compared with other glassy polymers, in sharp contrast to conventional wisdom that lowering interchain packing will bring about a loss in size-sieving power of the polymer. It is proposed that the relatively low carbon dioxide/methane permselectivity of the aryl-brominated PPOs is actually caused by their very low solubility-related selectivity. It is hypothesized that introduction of basic groups into the polymer repeat unit will enhance the solubility of carbon dioxide relative to methane in the polymer. Concurrently, if the packing density and torsional mobility of the polymer chain segments are also lowered (e.g. by bromine), the resulting polymer will exhibit both high carbon dioxide permeability and high permselectivity for carbon dioxide over methane. This project consists of a systematic experimental investigation of the above hypothesis. PPO polymers with different degrees of aryl-bromination, aryl- amination and aryl-phthalimidomethylation will be studied such that a wide range of packing densities and concentrations of basic groups is covered. Membrane gas separation technology will be one of the most important developing technologies of the next decade. Technological leadership in the area will also translate into increased manufacturing efficiency in all of the chemical process industry. This project, if the hypothesis described above is demonstrated to be correct, will constitute a major advance in membrane science which should translate into significant technical advances in membrane separations of gas mixtures.