Acceleration effect of ionic liquids on polycyclotrimerization of dicyanate esters

Abstract

The polycyclotrimerization reaction of dicyanate ester of bisphenol E (DCBE) in the presence of varying amounts (from 0.5 to 5 wt%) of 1-octyl-3-methylimidazolium tetrafluoroborate ([OMIm][BF4]) ionic liquid has been investigated using differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) techniques, after a curing stage at 150 °C for 6 h. It is noteworthy that an amount of [OMIm][BF4] as low as 0.5 wt% accelerates dramatically the thermal curing process leading to the formation of a polycyanurate network. The conversion of DCBE increased with increasing [OMIm][BF4] content in the temperature range studied. A reaction mechanism associated with the ionic liquid-catalyzed DCBE polycyclotrimerization is newly proposed via the involvement of a [CN]δ+–[OMIm]δ– complex as a key intermediate.

Keywords

• Polymer synthesis, molecular e
• Cyanate ester resins
• polycylotrimerization
• ionic liquid