The viscoelastic properties of poly(phenylene ethers). I. Unsubstituted and methyl or phenyl substituted polymers

A series of poly (phenylene ethers) with methy or phenyl substituents or without substituents have been studied. They are: M2PPO poly (2,6‐dimethyl p‐phenylene oxide), ϕ2PPO poly (2,6‐diphenyl p‐phenylene oxide), MϕPPO poly (2‐methyl, 6‐phenyl p‐phenylene oxide), H2PPO poly (p‐phenylene oxide), and H2PPS poly (p‐phenylene sulfide). Several sub Tg relaxation regions have been found for these polymers which seem to have a common mechanistic origin. The β region which was found for H2PPO (H2PPS), M2PPO, and ϕ2PPO has an activation energy, respectively, of ca. 12, 16, and 23 kcal/mole and is most probably due to hindered oscillatory motions of the backbone phenylene groups. The tan δ peaks at 1 cps occur, respectively, at ca. −110°, −50°, and +80°C. The next lower or γ region was found for MϕPPO and ϕ2PPO with an activation energy of ca. 12 kcal/mole and is probably due to hindered torsional oscillations of the side chain phenyl. A still lower relaxation region (called δ) was also found for the two last compounds. Its activation energy is ca. 4 kcal/mole and is most probably caused by some type of wagging motions of the side chain phenyl. No main chain relaxation was found for MϕPPO. All the relaxations have a very low intensity. The trend in the activation energies for the β region suggests that the barrier is intermolecular. An attempt to correlate the frequencies and activation energies of the β relaxations within the formalism of O'Reilly and Tsang gave good quantitative agreement.