Biobased Anethole-Functionalized Poly(phenylene oxides): New Low Dielectric Materials with High Tg and Good Dimensional Stability

A series of modified poly(phenylene oxides) (PPOs) with low dielectric constant, high Tg and good dimensional stability were developed. These polymers were synthesized by treating brominated PPOs with a biobased anethole and polymerized at a high temperature in the presence of a peroxide. When the molar ratios of anethole in the PPO were 0.2, 0.35 and 0.5, respectively, the cross-linked PPOs displayed low dielectric constants of less than 2.74 and high Tg (more than 220 °C). In particular, the PPO with 0.5 molar ratio of anethole exhibited a coefficient of thermal expansion (CTE, 23.4 ppm/°C) that is comparable to copper foil (ca. 18 ppm/°C). This result indicated that the modified PPOs are suitable for the production of copper-cladded laminates in electronic industry. Moreover, compared to a commercial PPO having a Tg of 153 °C and CTE of 155.8 ppm/°C, the modified PPOs with anethole units possessed a higher thermostability. Considering that PPOs are widely used in the electronics industry, this contribution offers a new approach to prepare high-performance materials using a biobased feedstock.