Tuning Microenvironment of Quaternary Ammonium Salt and Tertiary Amine Bifunctionalized Polyacrylonitrile Fiber for Cooperatively Catalyzed Aza-Michael Addition

A series of novel polyacrylonitrile fiber catalysts modified with different ratio of quaternary ammonium salt (QA) to tertiary amine (TA) were screened for heterogeneously catalyzed aza-Michael addition in water. The best catalyst was found to be PAN(PQ-1)F with a QA:TA ratio of 1:1, which can lead to high yield, excellent selectivity of solvent and great recyclability under optimized conditions. The special microenvironment of hydrophilic inner layer and hydrophobic surface layer of PAN(PQ-1)F is conducive to the leaving of the product and the high conversion of the reaction. Based on the fact that appropriate microenvironment combined with the catalytic sites promoted the reaction, cooperative effect of QA and TA in the microenvironment of PAN(PQ-1)F catalyst was proposed. [GRAPHICS] .