New Polyamides and Polyoxazoles Based on Diphenyl Ether Segments in the Polymers' Backbone

Abstract

Two new series of polyamides, 7 a-e and polyoxazoles 8 a-e , containing diphenyl ether segments were synthesized using a low-temperature solution of polycondensation and polycyclization reactions, respectively. Polyamides were synthesized by interaction of monomer 4 with different aliphatic and aromatic diacid chlorides, including adipoyl, sebacoyl, oxaloyl, 4,4′-azodibenzoyl and 3,3′-azodibenzoyl dichlorides. The poly-merization reaction was carried out in dry DMF as a solvent and in the presence of anhydrous potassium carbonate as a catalyst at room temperature. Polyoxazoles were obtained as cyclization products form corresponding polyamides in polyphosphoric acid. The model compounds 5 and 6 were synthesized to know the optimum polymerization procedures. The structure of the model compounds as well as the resulting polymers was characterized by elemental and spectral analyses. The synthesized polymers were soluble in protonic solvents such as formic and concentrated sulfuric giving different colors. The thermal properties of those polymers were evaluated by TGA, DTG, and DTA measurements and correlated to their structural units. FDT for polyamides was nearly complete at around 730–750°C, while for polyoxazoles it was nearly complete at around 580–650°C. The glass transition temperatures for the selected polymers were in the range of 47–74°C, while T m values were in the range of 156–315°C. X-ray analysis showed that the selected polyamides have a higher degree of crystallinity than polyoxazoles in the region 2θ = 5−60°. In addition, the morphological properties of selected examples were tested by SEM measurements. A comparative SEM study was carried out between selected polyamides and polyoxazoles.