Miscible blends of chemically‐modified poly(phenylene oxides) with styrene copolymers containing polar groups

Poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) is well‐known to be miscible with polystyrene, but immiscible with styrene copolymers containing polar groups. Certain nitrated‐PPOs (NPPOs) were found to be miscible with copolymers of styrene/acrylonitrile (SANs), copolymers of styrene/maleic anhydride (SMAs), a terpolymer of α‐methylstyrene/styrene/acrylonitrile (α‐MS/S/AN), and a copolymer of o‐ and p‐chlorostyrene (PCS). Also, certain simultaneously nitrated‐ and chlorinated‐PPOs (NCPPOs) were found to be miscible with SANs, SMAs and PCS whereas immiscible with the α‐MS/S/AN. The miscibility was indicated by the presence of a single composition‐dependent glass‐transition temperature for a given blend across the entire range of blend compositions tested. The miscibility of the aforementioned NPPOs and NCPPOs blends with SAN1 and SMA1 is attributed to hydrogen bonding of hydroxy groups of NPPOs and NCPPOs with nitrile groups and carbonyl groups, respectively, based on the literature information. The hydroxy groups were generated during nitration and simultaneous nitration/chlorination of PPO as a result of nucleophilic chain scission. Miscible blends of ‐NPPO/SAN and ‐NPPO/SMA with ABS1 showed a substantially better balance of the following properties than a comparable immiscible‐NPPO/SAN blend and a ‐PPO/SAN blend with ABS1: notched Izod impact strength, tensile properties, heat distortion temperature and gasoline stress‐crack resistance.Highlights Nitration and simultaneous nitration/chlorination of PPO generated hydroxyl end groups. Certain NPPOs and NCPPOs were miscible with SANs, SMAs and PCS. Miscibility indicated by a single composition dependent Tg for a given blend. Miscibility attributed to hydrogen bonding of respective functional groups. Impact‐modified miscible‐NPPO/SAN blends and ‐NPPO/SMA blends with ABS1 as impact modifier had good key properties.