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 -3 , 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 hydrophobicity 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.