Polyamides with pendant 1,3,4-oxadiazole and pyridine moieties

Abstract

A novel aromatic diamine, 2-(5-(3,5-diaminophenyl)-1,3,4-oxadiazole-2-yl)pyridine (POBD), containing a pyridine ring and a 1,3,4-oxadiazole moiety, was synthesized. It was used in a polycondensation with various aromatic and aliphatic diacid chlorides to generate a series of new aromatic polyamides with pendant 1,3,4-oxadiazole groups. The prepared polyamides were characterized by IR, elemental analysis and through the synthesis of model compounds. Thermophysical properties of the synthesized polyamides have been studied by DSC, TGA and inherent viscosity measurements. Relatively high inherent viscosity values (0.76–1.62 dL/g, in 0.125% H₂SO₄ at 25°C) were observed for these compounds. Number average molecular weight (M_n) of the polymers was measured by vapor phase osmometry (VPO). The introduction of bulky side chains in the structure of aromatic polyamides led to increased solubility of these polymers in common polar and aprotic solvents, such as DMF, DMSO, NMP and DMAc, which allowed thin films to be cast from polymer solutions. The highest molecular weight (M_n = 51190) was observed for polymer (IX), which was prepared from pyridine-2,6-dichlorocarbonyl.