Viscometric study of polystyrene in mixed solvents and with varying temperature

The viscometric behavior of polystyrene (PS) in a mixed solvent of toluene/ cyclohexane and with varying temperature was thoroughly investigated. It ha s been found that, in the plot of the reduced viscosity (eta(sp)/C) vs. con centration, the intrinsic viscosity of PS increased in the mixed solvent wi th higher ratio of toluene/cyclohexane or when measured at higher temperatu re, indicating that the polymer-solvent interaction increased in the mixed solvent with a higher ratio of toluene/cyclohexane or at higher temperature . According to the theoretical consideration discussed in the paper, the co rrelation between the intrinsic viscosity of PS at finite concentration, [e ta(PS)](C), and the concentration of PS in solution can be obtained by tran sforming the plot of the reduced viscosity (eta(sp)/C) VS. concentration of PS in the solvent. It is noted that [eta(PS)](C) decreased with an increas e in the concentration of PS in solution, indicating that the polymer dimen sions decreased in concentrated solution. The concentration-dependent inter molecular excluded volume effect, which can be quantitatively expressed by the parameter b(Y), is believed to be responsible for the results. In good solvent, the polymer coils expand, resulting in an increase of the intermol ecular excluded volume effect in solution. As a result, the parameter b(Y) in poor solvent is less than that measured in good solvent. In Theta-solven ts, the parameter b(Y) became zero, indicating that [eta(PS)](C) no longer changed with the increase of the concentration of PS in solution and that p olymer coils existed in an unperturbed state. (C) 1999 Elsevier Science Ltd . All rights reserved.