Intrinsic low-dielectric constant and low-dielectric loss aliphatic-aromatic copolyimides: The effect of chemical structure

Low-dielectric polymer materials are becoming essential for 5 G mobile communication to achieve mass transport information without signal loss. Herein, we present an aliphatic–aromatic copolyimide using Priamine 1075 (aliphatic) and m-tolidine (aromatic) as diamines. The branched bulky aliphatic units enlarge the free volume, effectively reducing the dipole moment density, while the aromatic diamine was introduced to prevent polymer chain relaxation under the operating conditions. We observed that there is an optimal composition that regulates the chain movement and density of dipole moments through the control of the polymer chain rigidity and nanostructure. Thus, by tuning the composition, we succeeded in achieving a low-dielectric copolyimide with a dielectric constant (Dk) of 2.63 and dielectric loss (Df) of 0.0017 at 28 GHz. Combining molecular design and composition control, this study suggests a design factor for advanced copolymers for telecommunication applications with fast signal transport speed and minimum signal loss.