Low-Dielectric Poly(aryl ether)s with High Thermal Stability Enabled by a Rigid Molecular-Hinge Strategy

As communication frequencies extend into the millimeter-wave and even terahertz ranges, signal transmission delay and energy dissipation become increasingly critical, imposing higher demands on the dielectric properties of polymer dielectrics. Consequently, materials combining low dielectric constant (D k ) and low dielectric loss (D f ) are urgently needed for high-frequency applications. Herein, aiming to further reduce the dielectric constant of the π-π stacking poly(aryl ether) system while preserving its thermal performance, we propose a "moderate molecular-hinge" modulation strategy and design two quinoxaline-based bis-halogenated monomers with distinct bond angles: M1 (120°) and M2 (60°, containing trifluoromethyl groups).Incorporating these monomers at a 16 mol% ratio yields the tetra-polymers PBEQ-M1 and PBEQ-M2, respectively. The introduction of rigid twisted units into the polymer backbone effectively increases free volume while suppressing dipole relaxation through conformational locking, achieving synergistic optimization of dielectric and thermomechanical properties. Dielectric property measurements reveal a significant improvement in the dielectric performance of the materials upon the introduction of the twisted monomers. At 15 GHz, PBEQ-M2 exhibits a D k of 2.291 and a D f of 0.00321—an order of magnitude lower than that of commercial poly(ether ether ketone) (PEEK) in the GHz range. Critically, this polymer also retains a balanced set of properties: a glass transition temperature of 314°C, a 5% thermal decomposition temperature of 577°C, a tensile strength of 80 MPa, a water absorption of 0.47%, and a coefficient of thermal expansion of 68 ppm/K. Among intrinsic poly(aryl ether)s with a glass transition temperature above 310°C, PBEQ-M2 exhibits the lowest reported dielectric constant and loss. Structural analysis reveals the distinct impacts of the two twisted configurations. While the 120° "flexible kink" of M1 increases free volume and lowers D k , its excessive disruption of chain rigidity leads to a significant decline in thermomechanical properties. In contrast, the 60° "rigid kink" of M2, synergized with trifluoromethyl groups, not only creates substantial free volume but also maintains local chain rigidity through its inherently stiff backbone. Furthermore, the low polarizability of the trifluoromethyl groups contributes to D k reduction, successfully achieving a balance between dielectric and thermomechanical performance. This study demonstrates that, building on a robust π-π stacking network, the introduction of a rigid twisted structure via molecular-hinge engineering effectively reduces the dielectric constant while preserving thermal performance, offering a viable paradigm for high-frequency dielectric materials.