Dual cross-linking strategy to prepare fluorine-containing poly(arylene ether nitrile) films with a low dielectric constant and ultra-low water uptake

Abstract

A low k-value in a humid environment is an important parameter for low dielectric materials, as the k-value is very sensitive to humidity. In order to obtain a low dielectric constant and improve water resistance, a series of poly(arylene ether nitrile) copolymers containing trifluoromethyl groups and two cross-linking sites of cyano and propenyl groups (DnAF-PEN) were designed and synthesized. The presence of the propenyl groups synergistically promotes the cross-linking of cyano groups; so dual cross-linked networks were constructed by a simple thermal treatment. With the change of the content of the cross-linkable group and cross-linking temperature, the properties of DnAF-PEN can be well tuned. The presence of the dual cross-linked networks and the introduction of trifluoromethyl allowed the films to exhibit excellent thermal and mechanical properties, a low dielectric constant (k = 2.26–2.43 at 1 MHz), hydrophobic surface (104.9–111.2°) and ultra-low water uptake (≤0.28%). Moreover, the k-value of the films remains stable for a long time in a humid environment. Furthermore, the cross-linked films were used to prepare flexible copper-clad laminates, which showed the highest peel strength of up to 6.64 N cm⁻¹. The excellent comprehensive properties make the cross-linked films excellent dielectric materials in both dry and humid environments.