Higher service temperature pressure sensitive adhesives were formulated from poly(styrene-b-isoprene-b-styrene) (SIS) block copolymer blended with low molecular weight midblock and endblock associating resins. The aliphatic midblock resin was WingTack 95® and the aromatic endblock resin was a polyphenylene ether, PPO. In even small amounts (< 3%) the PPO raised the service temperature of the adhesive, as measured by elevated temperature holding power (lap shear) tests. The formulations were also examined with transmission electron microscopy (TEM), small angle X-ray scattering (SAXS), dynamic mechanical analysis (DMA), and 180° peel strength tests. A tentative ternary phase diagram for SIS/WingTack 95®PPO was constructed and a basic understanding of structure/property relationships for this PSA system was accomplished. The large improvements in the elevated temperature holding power tests correlated with increases in the polystyrene microphase glass transition and order-disorder transition.