Curing kinetics of liquid crystalline 4,4′-Diglycidyloxybiphenyl epoxy cured with 4,4′-Diaminodiphenylsulfone

Liquid crystalline epoxy resins (LCERs) have been reported as a promising polymeric material with a high thermal conductivity. Among them, 4,4′-diglycidyloxybiphenyl (BP) epoxy with the simplest molecular structure for the formation of a liquid crystal (LC) phase appears most suitable for practical applications. In particular, it is known that BP epoxy cured by 4,4′-diaminodiphenylsulfone (DDS) exhibits a high thermal conductivity of 0.34 W/m K; however, their detailed curing reaction mechanism and kinetics have not been reported yet. Herein, the detailed mechanism and kinetics of the curing reaction between BP and DDS are reported. The curing reactions in the temperature range of 150–230 °C are investigated with the mixed model of the nth order and autocatalytic mechanism. The reaction order (m and n), reaction rate (dα/dt), rate constant (k₁ and k₂), and degree of conversion (α) are analyzed at several temperatures, where subscripts ₁ and ₂ represent the nth order and autocatalytic reaction, respectively. The kinetic parameters, activation energy, and pre-exponential factor, were determined as E_a1 = 60.76 kJ/mol, E_a2 = 57.20 kJ/mol, A₁ = 4.08 × 10⁴ min⁻¹, and A₂ = 101.22 × 10⁴ min⁻¹, which are in good agreement with the experimental data. Furthermore, the kinetic data could be utilized to predict and control the curing behaviors and the properties of the LCER for further application.