Oligomer engineering enabling high-performance Poly(phenylene oxide) resins for high-frequency/speed copper clad laminates

Poly(phenylene oxide) (PPO), recognized for its exceptional dielectric properties, serves as a preferred matrix resin for high-frequency and high-speed copper-clad laminates (CCLs). However, research on functionalized PPO resins is constrained by synthesis challenges, relying primarily on two commercial resins with fixed molecular weights/distributions and insufficient end-group functionalization. These exhibit performance bottlenecks in higher-grade CCLs applications, and crucially, lack systematic studies on the structure-processing-property relationships governed by tunable precursor oligomer polymerization degrees (DP). This work employs precursor oligomer engineering via direct copolymerization with methacrylic anhydride (MMA) as the capping agent to synthesize a series of PPO n -MMA oligomers (DP, n = 5–25) featuring an ultrahigh difunctional group content (>97%). These oligomers were blended with hydrocarbon resin, flame retardant, and crosslinker to prepare glass fiber-reinforced composites. Results demonstrate that the oligomer (DP, n = 5) significantly dictates processing behavior and performance: the system exhibits a minimum viscosity of 80 Pa·s (much lower than 700 Pa·s for commercial resin), a 38.6% increase in flexural strength, a glass transition temperature ( T g ) elevated to 241 °C, and a 96.7% increase in crosslinking density. The coefficient of thermal expansion (CTE) value is reduced to 8.6 ppm/°C (40-240°C). Furthermore, it achieves an extremely low dielectric loss ( D f = 0.0044) at 10 GHz with weak frequency dependence. This oligomer engineering strategy delivers superior processability, thermal resistance, mechanical strength, and dielectric properties. It elucidates the critical DP–processing–performance relationships, providing fundamental insights and technical pathways for developing high-performance functionalized low-molecular-weight PPO resins for next-generation high-frequency/high-speed CCLs. • A series of PPO oligomers of varied polymerization degrees were synthesized. • PPO oligomers with ultra-high bifunctional group content (>97%) were synthesized • The polymerization degree–processing–performance relationship were elucidated. • PPO oligomers exhibit excellent processing, mechanical, and thermal properties. • Oligomer engineering unlocks new pathways to tailor PPO for CCL applications.