Green and rapid preparation of thermally stable and highly organosoluble polyamides containing L-phenylalanine-9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboximido moieties

A chiral diacid monomer containing L-phenylalanine-9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboximido unit was successfully synthesized in four steps and used in the preparation of a series of novel optically active polyamides by direct polycondensation with diverse aromatic diamines using 1,3-dipropylimidazolium bromide under microwave dielectric heating. Ionic liquids (ILs) efficiently absorb microwave energy and thus are employed as solvent. By controlling the concentration of 1,3-dipropylimidazolium bromide, reaction time and power level, high yield and moderate inherent viscosity polymers could be achieved in a very short period of time. All the resulting polymers exhibited excellent solubility in various organic solvents. The polyamides were found to have inherent viscosities in the range of 0.54-0.85 dL g(-1). These polyamides had glass-transition temperatures (T(g)) above 180 degrees C, and a 10% weight-loss temperatures in excess of 340 degrees C with char yield at 800 degrees C in nitrogen higher than 40%. A comparative study on effects exerted by microwave technique with conventional method is also presented. Copyright (C) 2009 John Wiley & Sons, Ltd.