Polyphenylquinoxaline (PPQ-E) is an aromatic heterocyclic polymer with high performance and water resistance at high temperature.It was synthesized form aromatic tetraamine and aromatic tetraketone by condensation polymerization.The influence of physical aging on structure and mechanical properties of polyphenylquinoxaline has been studied.The free volume and cohensional entanglement structure of samples preapared under two different thermal conditions were measured by positron annihilation life spectroscopy (PALS) and DSC.For samples which underwent physical aging an endothermic peak at the end of the glass transition was observed in a heating process.It means more cohensional entanglement stucture forms during physical aging.The results of PALS show that physical aging may reduce the free volume in samples.A little increase of storage modulus in the temperature range from 100℃to300℃ and a decrease of mechanical loss at 250～300℃ result form physical aging.The tensile mechanical test manifest that physical aging may result in a decrease of fracture strain and energy

an increase of yield stress and a transition from ductile to brittle generate for PPQ-E samples.