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

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<jats:title>Abstract</jats:title><jats:p>The radius of gyration <jats:italic>R</jats:italic><jats:sub><jats:italic>g</jats:italic></jats:sub>, the hydrodynamic radius <jats:italic>R</jats:italic><jats:sub><jats:italic>h</jats:italic></jats:sub>, 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<jats:sup>5</jats:sup> ≤ <jats:italic>M</jats:italic><jats:sub><jats:italic>w</jats:italic></jats:sub> ≤ 5.47 × 10<jats:sup>6</jats:sup> 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 <jats:italic>R</jats:italic><jats:sub><jats:italic>h</jats:italic></jats:sub>/<jats:italic>R</jats:italic><jats:sub><jats:italic>g</jats:italic></jats:sub> 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 <jats:italic>R</jats:italic><jats:sub><jats:italic>h</jats:italic></jats:sub> and/or <jats:italic>R</jats:italic><jats:sub><jats:italic>g</jats:italic></jats:sub> 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.</jats:p>

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