Synthesis and characterization of s-histidine-derived poly (ionic liquid)/silica nanocomposites and their application in the enantioselective hydrolysis of a chiral ester



In this study, a new optically active monomer containing two chemically preformed imide rings was synthesized. The monomer was then used to synthesize optically active poly(amide imide)s (OAPAIs) and an optically active polyionic liquid (OAPIL), which were finally reacted with various amounts of silica nanoparticles in an in situ polymerization reaction to produce OAPAI/SiO2 and OAPIL/SiO2 hybrid materials containing sulfonic acid groups. The prepared monomers and the OAPAI and OAPIL nanocomposites were characterized by 1H-NMR spectroscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and differential scanning calorimetry. OAPIL/SiO2 served as an excellent catalyst in water as a solvent for the hydrolysis of d,l-phenylglycine methyl ester with the advantage of a markedly enhanced enantioselectivity and activity. Also, the enantioselectivity was strongly dependent on the SiO2 content in the OAPIL/SiO2 systems; a favorable SiO2 content was 20% (w/w). The enantioselectivity was 95.2% (substrate conversion = 62.3%). © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39595.