The copolymer has been synthesized by condensation of p-hydroxy benzoic acid and
formaldehyde in 2M HCl. The terpolymer has been synthesized by condensation of p-hydroxy
benzoic acid, urea and formaldehyde in 2M HCl. Density (ρs), ultrasonic velocity (Us) and
viscosity (ηs) of terpolymer and copolymer have been measured in DMF at five different
temperatures.The experimental data have been used to calculate the acoustical parameters
namely acoustic impedance (z), adiabatic compressibility (βs), intermolecular free length (Lf).
The results are discussed in the light of solute-solvent interaction and structural effects on the
solvent in solution.