HYDRODYNAMIC RADIUS AND INTRINSIC-VISCOSITY OF POLYSTYRENE IN THE CROSSOVER REGION FROM THETA-SOLVENT TO GOOD-SOLVENT CONDITIONS

The radius of gyration R//g, the hydrodynamic radius R//h, and the intrinsic viscosity left bracket eta right bracket have been measured for polystyrene in cyclohexane (at the theta temperature and 44. 5 degree C), 2-butanone (at 30 degree C), and toluene (at 30 degree C) in the molecular weight range 2. 38 multiplied by 10**5 less than equivalent to M//w less than equivalent to 5. 47 multiplied by 10**6 to elucidate the excluded-volume effects on dynamical behavior in dilute polymer solutions in the crossover region from theta to good-solvent conditions. The results are compared with theoretical predictions of current thermal blob theories and the Pade approximant theory of Tanaka. It is found that the ratio of R//h/R//g decreases with an increase in the excluded-volume effect, following the prediction of the simple blob theory, but that its magnitude is about 15% higher than the theoretical value. Experimental variation of left bracket eta right bracket with R//h and/or R//g lies in between predictions of the scaling law and the Pade approximant. The concentration dependence of the diffusion coefficient is also compared with predictions of current theories.