Alkyl Side-Chain-Induced Improvement of Dielectric Properties of Polymers. 1. Fluorene–Benzocyclobutene-Based Polymers

Alkyl side chains have been demonstrated to significantly affect the interchain packing of π-conjugated polymers, while their potential for modifying low-k materials remains unexplored. Herein, four low-k nonconjugated polymers based on the fluorenyl group with linear alkyl side chains of different lengths have been prepared. With the increase of the side chain length, their dielectric constants (Dk) gradually decrease. For example, when the side chains are butyl, hexyl, dodecyl, and octadecyl, the Dk values of the polymers are 2.62, 2.59, 2.50, and 2.45, respectively. Moreover, the polymers also display dielectric loss (Df) values of below 5.0 × 10–4 at 10 GHz. This discovery indicates that the alkyl side chains also have a big effect on the dielectric properties of the nonconjugated polymers via disrupting the close packing of the polymer chains, inducing the improvement of the dielectric properties of the polymers. This contribution provides a new strategy for the design of low-k materials used in the microelectronic industry.