Effect of temperature and solvents on ultrasonic speed and thermo-acoustic parameters of epoxy resin of (2E, 6E)-bis (4-hydroxy benzylidene)-4-methylcyclohexanone solutions at four different temperatures

ABSTRACT

The density (r), viscosity (h) and ultrasonic speed (U) of 1, 4-dioxane (DO), tetrahydrofuran (THF), chloroform (CF) and solutions (0.25-5 wt%) of epoxy resin of (2E, 6E)-bis(4-hydroxy benzylidene)-4-methylcyclohexanone have been investigated at 298, 303, 308 and 313 K to understand molecular interactions in solutions of different polarity. Various acoustical and thermodynamic activation parameters such as acoustical impedance (Z), adiabatic compressibility (k_a), internal pressure (p), free volume (V_f), intermolecular free path length (L_f), van der Waals constant(b), viscous relaxation time (t), classical absorption coefficient (a/f²)cl, Rao`s molar sound function (R_m) and solvation number (S_n) were determined using r, h and U data and correlated with concentration (C) at four different  temperatures (T). Good to excellent correlation between a given parameter and concentration is observed at all T. Linear or non-linear increase or decrease of studied acoustical and thermodynamic parameters with concentration of epoxy resin at different temperatures indicated existence of strong molecular interactions (solvent-solute and solute-solute) in the solutions. The non-linear increase of Sn with concentration of epoxy resin further supported the existence of strong molecular interactions and structure forming tendency of EMBHBC. The competing solvent-solute and solute-solute interactions are also supported by thermodynamic activation parameters (DG^*, DH^* and DS^*).