Phase-controllable topochemical polymerization of liquid crystalline epoxy according to spacer length

Abstract

Liquid crystalline epoxies (LCEs) have received considerable attention owing to their potential applications in heat dissipation in electronic devices. Herein, we report novel LCE systems (LCE_n, n = spacer length) comprising bifunctional phenyl benzoate LC monomers with different spacers that are cured using an imidazole curing agent. Based on microstructural analyses, the lengths of the different alkyl chains considerably affect the LC phases. LCE₄ and LCE₆ exhibit smectic orientations, whereas LCE₈ exhibits a nematic orientation during polymerization. All LCE_n samples exhibit high thermal conductivities and superior thermal properties because the mesomorphic assemblies enhance their strong intra- and intermolecular interactions. LCE₄, in particular, which displays a compact orientation order, exhibits remarkably high thermal conductivity (0.49 W m⁻¹ K⁻¹). Furthermore, the LCE_n samples exhibit superior thermal conductive behavior to those of existing commercial polymers. These results suggest the potential of LCEs as electronic materials based on their thermomechanical properties and high thermal conductivities.