AbstractMixtures of phenoxy, (a polyhydroxyether of bisphenol A) with respectively ethylene–propylene copolymer containing grafted anhydride groups along the chains (EP‐g‐MA), terpolymers of ethylene, t‐butyl acrylate and acrylic acid (EAA), and the sodium ionomer of a terpolymer of ethylene alkyl acrylate and methacrylic acid (I), were produced on a 25 cc torque rheometer. Small amounts of different organic sodium compounds, exhibiting varying levels of base strength, were also used to catalyze the reaction between the functional groups of the two polymers in the mixture. It was found that whereas EP‐g‐MA reacted with phenoxy to produce both graft copolymers and cross‐linked products in varying amounts, the terpolymers containing carboxylic acid groups in the backbone of the polymer chains would never give rise to the formation of cross‐linked products even when large amount of a strong base, such as sodium ethoxide, was used to catalyze the reactions. The latter mixtures exhibited the characteristics of ionomers, involving also alkoxide anions from the phenoxy component to an extent which depended on the base strength of the sodium compound used. The ionomeric mixtures displayed morphological features varying from finely dispersed particles to cocontinuous phases. © 1994 John