Hydrodynamic radius and intrinsic viscosity of polystyrene in the crossover region from θ to good‐solvent conditions

The radius of gyration R g , the hydrodynamic radius R h , and the intrinsic viscosity [η] have been measured for polystyrene in cyclohexane (at the θ temperature and 44.5°C), 2‐butanone (at 30°C), and toluene (at 30°C) in the molecular weight range 2.38 × 10 5 ≤ M w ≤ 5.47 × 10 6 to elucidate the excluded‐volume effects on dynamical behavior in dilute polymer solutions in the crossover region from θ 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 [η] 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.