Effect of Alkyl Chain Tail on Thermal Conductivity and Physical Properties of Side-Chain Liquid Crystalline Polymers

Abstract

Thermally conductive polymers have gained scientific attention for improving heat dissipation in electric devices. Their thermal conductivity is enhanced by optimizing the network molecular alignment. Liquid crystal, through intermolecular interaction, achieves high orientation levels, thereby enabling superior thermal conductivity. This study aims to demonstrate the thermal conductivity of polymers derived from liquid crystal materials by synthesizing a series of liquid crystal monomers, EP_n, based on a phenyl benzoate mesogen core. The EP_n monomers are designed with epoxide functional groups with various alkyl chain tails (n = 3, 4, 5, 8). Side-chain polyethylene glycols (P-EP_n series) are synthesized through anionic ring-opening polymerization using potassium tert-butoxide. The effect of the introduced aliphatic chain tail on structural orientation and physical properties is investigated, revealing significant effects on phase transition behavior and thermal conductivity. In addition, P-EP_n exhibits higher thermal decomposition temperature (> 360 °C) compared to conventional polyethylene glycol, with P-EP₅ achieving the highest thermal conductivity of 0.42 W m⁻¹ K⁻¹ in the P-EP_n series.