A facile and highly efficient protocol for synthesis of poly(ether sulfone)s in ionic liquid/zwitterion

A benign approach for efficient preparation of poly(ether sulfone) (PES) (η _inh = 0.10?0.31 dL?g^?1) has been presented by using ionic liquid (IL)/zwitterion (ZI) as reaction medium. It has been found that the interaction between 4,4′-dihydroxydiphenylsulfone (Bisphenol-S) and ZI at elevated temperatures results in efficient reduction of dehydration time, which is confirmed by TGA curves, melting point of the mixture and FTIR spectra. Furthermore, no agglomeration is observed at dehydration stage, which is attributed to the high solubility of Bisphenol-S dipotassium salt in IL/ZI. This also makes the polymerization temperature (150 °C) much lower than a conventional method (220?300 °C). In order to demonstrate the efficiency of IL/ZI as reaction medium, the polymerization was also performed in sulfolane under the same reaction condition as that in IL/ZI.