Leveraging Lignin's Ortho-Methoxy Groups for Intramolecular Hydrogen Bonding to Reduce Dielectric Constant of Epoxy Resins

Abstract

This work proposes a practical intramolecular hydrogen bonding strategy to reduce the dielectric constant (D k ) of epoxy resins by harnessing lignin's intrinsic ortho-methoxy groups as structural modulators. The escalating demand for highspeed electronics has driven the need for low-D k materials; however, conventional strategies are plagued by complex molecular design, high costs, and compromised thermomechanical performance. Herein, in contrast to resource-intensive demethoxylation approaches, we retain the characteristic methoxy groups of lignin to form intramolecular hydrogen bonds with hydroxyl groups generated during epoxy curing. This mechanism effectively shields polar groups (primary contributors to high D k ), reducing D k from 4.37 (conventional analog) to 3.75 at 1 MHz. The networks exhibit exceptional hygrothermal stability, with a glass transition temperature (T g ) decline of ≤2 °C and retention of ~94.2% tensile strength and ~93.7% modulus after 15 days of aging at 90% relative humidity and 60 °C. This work not only provides a novel method for reducing Dk but also innovatively valorizes lignin's characteristic methoxy groups, offering a sustainable platform for advanced microelectronics.