Chinese Journal of Polymer Science Vol. 28, No. 2, (2010), 147−155 Chinese Journal of Polymer Science © Chinese Chemical Society Institute of Chemistry, CAS Springer-Verlag Berlin Heidelberg 2010 SYNTHESIS AND CHARACTERIZATION OF ORGANOSOLUBLE POLYAMIDES FROM QUINOXALINE BASED DIAMINE Hossein Mighani a, b* and Mousa Ghaemy b a Department of Chemistry, University of Golestan, Gorgan, P.O. Box 155, Iran b Department of Chemistry, University of Mazandaran, Babolsar, P.O. Box 453, Iran Abstract Aromatic/aliphatic polyamides were synthesized from a diamine monomer, 2,3-bis-p-aminophenylquinoxaline (IV), based on quinoxaline and various dicarboxylic acids of aliphatic, aromatic and heterocyclic. The diamine and polyamides were characterized by elemental analysis, FTIR and 1 H-NMR. The solubility of the polyamides was affected by the quinoxaline and heterocyclic groups in the polymer chain. They were all soluble in common organic solvents such as dimethylsulfoxide (DMSO), N,N-dimethylformamide (DMF) and N-methylpyrolidone (NMP). The polyamides showed inherent viscosity in the range of 0.25−0.3 dL/g in DMSO at 25°C and good thermal stability with the char yields in the range of 65%−82% at 600°C in nitrogen. Keywords: Quinoxaline; Polyamides; Solubility; Thermal stability. INTRODUCTION Aromatic polyamides are well known as high performance engineering thermoplastics and have been widely used in various industries because of their good thermal stability, chemical resistance and mechanical properties [1] . However, their poor solubility in many organic solvents and also high softening or melting temperatures caused by their rigid structures and high stiffness of the polymer backbone or high crystallinity lead their process ability difficult. With the ever increasing demand for new processable engineering plastics, attempts have been oriented to the introduction of substituents having various chemical structures onto the benzene rings of monomers, the use of monomers containing several benzene rings separated by flexible bridges, or the use of heterocyclic monomers [2−6] . Another approach to increasing the processability is the introduction of a bulky pendant group [7] or a polar, rigid and zigzag group (heterocyclic monomer) into the main chains of polyamide [8−10] . Among various heterocyclic units which have been introduced into the main chain of aromatic polyamides, the phenylquinoxaline rings proved to be very beneficial [11, 12] . Such modifications in the aromatic backbone of polymers cause a decrease in the crystallinity and improve solubility in organic solvents and therefore better capability to be processed from solutions, while maintaining a high thermal resistance [13, 14] . Preparation of polyamides based on quinoxaline ring and its related derivatives has been under investigation by many researchers. Akutsu et al. has prepared aromatic polyamides containing quinoxaline ring by transformation of α-diketone moieties in the main chain [15] and by polycondensation of 4,4′-(2,3-quinoxalinediyl)dibenzoyl chloride and 4,4′-(2,3-benzo[g]quinoxalinediyl)benzoic acid with aromatic diamines [16−19] . They have also reported the preparation of polyamides and polyimides from 2,3-bis(4-aminophenyl)quinoxalines and aromatic dicarboxylic acids and tetracarboxylic dianhydrides [20, 21] . Hedrick et al. [22] reported preparation of polyimide * Corresponding author: Hossein Mighani, E-mail: hmighani@umz.ac.ir Received December 4, 2008; Revised January 25, 2009; Accepted February 10, 2009 doi: 10.1007/s10118-010-8231-x