Miscibility of nitrated poly(phenylene oxide) and styrene–acrylonitrile copolymer blends

Abstract Poly(2,6‐dimethyl‐1, 4‐phenylene oxide) (PPO) is a well‐known high heat‐resistant polymer and miscible with polystyrene. However, it is not miscible with many polymers containing polar groups. In the present study, PPO was nitrated to prepare a nitrated PPO (NPPO) containing polar nitro groups and blended with a copolymer of styrene/acrylonitrile (SAN). Dynamic mechanical analysis (DMA) data showed that NPPO in SAN‐rich phase was miscible with SAN, while NPPO in NPPO‐rich phase was partially phase‐separated from SAN, both over the entire blend composition range from NPPO wt. fractions of 0.1–0.5 investigated for this work. Analyses of Fourier‐transform infrared (FTIR) and ultra‐violet (UV–VIS) spectra indicated that the miscibility of NPPO with SAN was caused by intermolecular hydrogen bonding of CN group of SAN with OH end‐group of NPPO in the NPPO/SAN blends. NPPO's OH end‐group, meta‐nitro 2,6‐dimethyl phenol, was produced during nitration of PPO due to chain scission of aryl ether bond. Besides the intermolecular hydrogen bonding, dipole‐diplo interaction of the CN and nitro groups resulted in dissociation of the CN dimers and trimers to the CN monomers in the NPPO/SAN blends.