Heat Capacity of Nematogenic N-p-Ethoxybenzylidene-p′-butylaniline between 14 and 375 K

The heat capacity of a low-temperature liquid crystal EBBA (N-p-ethoxybenzylidene-p′-butylaniline) of 99.75% (mol) purity was measured in the range 14–375 K with an adiabatic calorimeter. The melting point Tm was 305.62 K, and the enthalpy and entropy of fusion 27.09 kJ mol−1 and 88.71 J K−1 mol−1, respectively. The temperature of mesomorphic transition Tc from nematic to isotropic liquid was 349.08 K, and the enthalpy and the entropy changes due to the mesomorphic transition were 1.553 kJ mol−1 and 4.524 J K−1 mol−1, respectively. Excess heat capacity due to the mesophase transition, C(excess), is represented by C(excess)∼ε−0.7 in the range 10−4<ε<10−1.5, where ε≡|T–Tc|⁄Tc. This implies that the mesomorphic transition of EBBA can be regarded as of critical phenomena, characterized by a second-order rather than a first-order nature.