A simple method to synthesize high Tg sulfonated ionomers based on catalytic insertion polynorbornene is reported. Copolymers of norbornene and 5-methyl alcohol norbornene (endo:exo = 82:18) or 5-methyl bromide norbornene (endo:exo = 86:14) as well as terpolymers of norbornene, 5-methyl alcohol norbornene and 5-hexyl norbornene are prepared using a cationic Pd catalyst. These copolymers are then thioacetylated. Using hydrogen peroxide as oxidant, a sulfonated polynorbornene is obtained. Ionomers containing as much as 30 mol% SO3H and with Tgs above 200 degrees C are obtained in a four-step procedure of overall 40-75% yield. (C) 2016 Elsevier Ltd. All rights reserved.