Synthesis and Dielectric Properties of Star‐Shaped Poly(Phenylene Oxide) Resins

ABSTRACT High‐frequency copper‐clad laminates require thermosetting resins with low dielectric loss, high thermal resistance, and good melt processability. However, high‐molecular‐weight linear poly(phenylene oxide) (PPO) suffers from poor melt flowability, while molecular‐weight reduction can compromise network rigidity. In this work, a four‐arm star‐shaped vinyl‐terminated PPO precursor (sPPO‐V) was synthesized using tetrafunctional initiator TDPE. Molecular‐weight‐matched high‐molecular‐weight linear PPO (HMW‐PPO) was prepared as a control to evaluate the effect of molecular architecture. SEC, 1H NMR, and FT‐IR analyses confirmed the successful synthesis of the star‐shaped precursor. Rheological measurements demonstrated that sPPO exhibited reduced melt viscosity compared with linear PPO controls, including HMW‐PPO with comparable molecular weight. After curing, sPPO‐V showed an increased glass‐transition temperature of 220°C, together with improved dielectric properties ( D k = 2.50, D f = 2.11 × 10 −3 at 1 GHz), thermal stability ( T d5 = 330°C), and moisture resistance (water contact angle of 98.3° and water uptake of 0.18% after 72 h). The enhanced performance was attributed to the multi‐arm architecture‐induced topological constraints and reduced molecular packing efficiency. This work demonstrates that molecular architecture engineering is an effective strategy for balancing processability, thermal rigidity, dielectric performance, and moisture resistance in PPO‐based thermosetting resins.