Alkyl-Side-Chains Induced Improvement of Dielectric Properties of Polymers. 3. Cardanol-based Low-k Materials

Based on our previous discovery that alkyl-side-chains in the aryl polymers have a positive effect on dielectric properties of the polymers, this work further investigates the side-chain effect by a hydrogenated bio-based cardanol monomer with a long pentadecyl alkyl side chain. The monomer was functionalized by introducing the thermocrosslinkable benzocyclobutene groups, and its cured product displayed a dielectric constant ( ε ) of 2.59 and a dielectric loss ( tan δ ) of 5×10 -4 at a high frequency of 10   GHz. In contrast, a controlling polymer with methyl side chain exhibited a ε of 2.84 and a tan δ of 1.4×10 -4 , respectively. Such data indicate that the long alkyl-side-chains can effectively improve the dielectric properties of the aryl polymers. Moreover, the cured hydrogenated bio-based cardanol also exhibited good hydrophilic properties with the water absorption of 0.16% even immersing it in boiling water for 96   h. These results imply that bio-based cardanol is a potential candidate for the preparation of the low- k materials used in microelectronic industry.