Biobased Low-k Polymers at High Frequency Derived from Isoeugenol

Two biobased functional monomers (M1 and M2) derived from isoeugenol have been successfully prepared through the Ullmann–Ma and the Piers–Rubinsztajn reactions in an overall yield of more than 81%. These two monomers have also been converted into the cross-linked polymers by a thermo-curing reaction. The obtained polymers display good thermostability, hydrophobicity, and low-dielectric performance. Among them, cured M1 exhibits a higher glass transition temperature (Tg) of 384 °C and a lower coefficient of thermal expansion (CTE) of 53 ppm/°C in a range of the temperatures from 25 to 350 °C, while cured M2 displays good dielectric properties with a dielectric constant (Dk) of 2.53 and a dielectric loss (Df) of 1.21 × 10–3 at a frequency of 5 GHz. Such good dielectric properties for cured M2 remain stable even keeping it in boiling water for 96 h. The thermo-curing reaction of the mixture of two monomers in a molar ratio of 1:1 was also investigated and the results indicated that the formed polymer (cured B1) had good comprehensive performances with a Tg of 265 °C, CTE of 67 ppm/°C, Dk of 2.62, and Df of 1.96 × 10–3. Such data are superior to those of many commercial dielectric materials, suggesting that the two biobased monomers are suitable as the precursors of dielectric materials for the application in high-frequency communication.