Ultrasonic Velocity Study of Poly (R, R', 4,4'-cyclohexylidene Diphenylene Toluene-2, 4-disulfonates) Solutions at 30°, 35° and 40° C

Ultrasonic velocity (2 MHz) and acoustical parameters of poly (R, R', 4, 4'-cyclohexyli-dene diphenylene toluene-2, 4-disulfonates) (PS-3: R=R'=Cl and PS-4: R=CH₃ and R'=Cl) solutions investigated to understand the effect of methyl and chlorine substituents on molecular interactions. The linear increase of ultrasonic velocity (U), acoustical impedance (Z), Rao's molar sound function (R), Van der Waals constant (b) and internal pressure (π); and nonlinear increase of classical absorption coefficient (α/f²)Cl and viscous relaxation time(τ) with C and decrease with T; and linear decrease of isentropic compressibility (κ_S) relaxation strength (r), free length(L_f) and free volume (V_f) (nonlinear) with concentration (C) and increase with temperature(T) suggested the existence of powerful molecular interactions and hence solvophilic nature of the polymers, which is supported by positive values of solvation number (S_n). Structural modification (entanglement) is found above 2% concentration in 1,2- dichloroethane and THF systems. The linear increase of S_n with C and T indicated the presence of predominant polymer-solvent interactions over polymer-polymer interactions. The decrease of S_n with T is due to breaking of structure by predominant thermal energy over molecular interaction energy.