可自交联聚酰亚胺的合成及气体分离用不对称中空纤维膜的制备

As a gas separation membrane material, polyimide shows high permeability and selectivity, along with the excellent mechanical properties and high thermal stability. However, the issues on the anti-plasticizing capacity of the material and the forming process of the hollow fiber membranes limit the extensive applications of the polymer in the "green" chemical separation areas. To this end, on account of separating CO2/CH4 gas mixture and based on the molecular design, functional groups and benzene alkyne reactive side group will be introduced to the macromlecular chain to improve separation performance and to enhance the anti-plasticizing capacity of polyimide due to the crosslinking reaction of the active groups between inter-chains. The copolymerization method will be employed to synthesize spinnable polyamic acid (i.e., the precursor of polyimide) solution in mixed solvents. The polyamic acid asymmetric hollow fiber membrane can be prepared by adjusting the forming process of the fiber membrane with the functional layer and the support layer. And then, the polyamic acid is converted to the polyimide by the cyclization reaction at the high temperature. Meanwhile, the crosslinking reaction of benzene alkyne happens to obtain the polyimide asymmetric hollow fiber membrane with the thin and dense functional layer and porous support layer. It will be revealed that the relationship among the chemical structure of the polymer, microstructure and morphology, and gas separation performance of the fiber membrane, providing the theoretical basis and technical support for the preparation of high-performance hollow fiber membrane.

作为气体分离膜材料，聚酰亚胺不仅表现出较高的渗透性和选择性，而且具有优良的机械性能和较高的热稳定性，但该材料的抗塑化能力及中空纤维膜的加工成形等问题限制了其在“绿色”化工分离领域的广泛应用。为此，本项目针对CO2/CH4混合气体的分离，从分子结构设计着手，将功能性基团和具有反应活性的苯炔侧基引入聚合物链中，在改善分离性能的同时，通过纤维膜成形后的大分子链间交联反应提升聚酰亚胺的抗塑化能力。采用共聚手段在混合溶剂中合成可纺性的聚酰胺酸（聚酰亚胺的前驱体）溶液，通过调节纺丝过程中纤维膜功能层和支撑层的成形过程制备聚酰胺酸不对称中空纤维膜；高温使聚酰胺酸发生环化反应生成聚酰亚胺，同时大分子间的苯炔发生交联反应，从而制备功能层薄而致密、支撑层多孔的聚酰亚胺不对称中空纤维膜。揭示聚合物的化学结构、纤维膜的微观形态及分离特性的相互关系，为高性能中空纤维膜的制备提供理论基础和技术支撑。

本项目针对工业领域CO2气体分离的应用需求，设计并制备了聚酰亚胺非对称中空纤维膜。通过分子结构设计，将刚性大体积基团（例如Tröger's Base）及反应性侧基（邻羟基等）引入聚酰亚胺大分子链中，合成可纺性聚合物纺丝溶液，研究了纤维膜成形过程中溶胶-凝胶转变与微结构的相互关系，建立了中空纤维膜微观形态结构的调控机制，通过高温环化及分子链间的自交联反应，构筑了“分离层薄而致密、支撑层疏松多孔”的非对称聚酰亚胺气体分离膜，在兼顾渗透性和选择性的同时有效提升了分离膜的抗塑化能力。目前，所制备的聚酰亚胺中空纤维膜的外径可低至250-300 nm，内径100-200 nm，CO2渗透通量达到330 GPU，CO2/CH4分离系数接近40。所制备的高性能聚酰亚胺中空纤维膜在天然气、沼气分离提纯、工业烟道气CO2分离、飞机油箱富氮惰化保护等领域具有广泛的应用前景。本项目相关研究结果已经申请国家发明专利5项，其中授权专利3项；发表SCI收录论文21篇。培养博士研究生4名，硕士研究生5名。