Enhanced intrinsic thermal conductivity of aromatic polyesters through dual strategies of hydrogen bonding and π-π stacking

Aromatic polyesters are widely used in microelectronics, medical devices, and new-energy vehicle batteries. However, their low intrinsic thermal conductivity (λ) limits their effectiveness in dissipating heat from high-power components. Intermolecular interactions such as hydrogen bonds and π-π stacking are effective for enhancing the λ of aromatic polyesters. In this work, 5-(n-alkoxy-Cam-AmBiph)IPA (IPA) with an amide bond, biphenyl unit and varying-length alkyl is synthesized first. Three types of intrinsically thermally conductive side-chain poly(4,4′-dihydroxybiphenyl isophthalate) (S-PDI) are prepared using IPA and 4,4′-biphenol as the main monomers through solution polycondensation and “solution coating-stacking-hot pressing” process. The results demonstrate that the length of the side-chain alkyl spacer effectively controls the hydrogen-bond density. The seven-methylene spacer promotes the densest hydrogen-bonding network in S-PDI, and the combined effect of hydrogen bonding and π-π stacking thus significantly enhances its intrinsic thermal conductivity. The highest λ of S-PDI reaches 0.36 W/(m K), representing a 140.0% increase over the λ (0.15 W/(m K)) of commonly used polyethylene terephthalate. The corresponding elasticity modulus, hardness, glass transition temperature, and heat resistance index are 3.7 GPa, 214.2 MPa, 112.6 °C, and 183.5 °C, respectively.