Intrinsic viscosities were determined at 25 °C for 10 samples of narrowly distributed sodium polystyrene sulfonate (the molecular weights M ranging from 0.9 to 1000 kg/mol) in pure water and in aqueous solutions containing 0.9 wt % NaCl from the slope of ln ηrel versus polymer concentration. In the middle range of M, the [η] values are in the former case almost 2 orders of magnitude larger than in the latter case. In the absence of salt, the plot of log [η] as a function of log M exhibits a sigmoidal shape, which can be approximated within the interval 3 < M (in kg mol-1) < 30 by log[η] = −0.17 + 2.1 log M. In the presence of salt, the following relation holds true in the entire regime:  log[η] = −0.13 + 0.86 log M. The concentration dependences of η of the present polyelectrolyte solutions and of solutions of uncharged polymers in organic solvents taken from the literature can be modeled quantitatively by means of recently reported relations at least up to reduced polymer concentration c[η] = 5. The physical meaning of the parameters obtained from this modeling is surveyed.

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Equilibrium vapor pressures, p, are reported for the systems tetrahydrofuran + poly(vinyl methyl ether) and tetrahydrofuran + polystyrene at 20, 40, and 60 °C. These data plus information from the literature serve to demonstrate that the composition dependence of p can be modeled quantitatively for polymer solutions in thermodynamically very different solvents by means of three, physically meaningful parameters.

The Flory‐Huggins interaction parameter χ is determined as a function of volume fraction of polymer φ by vapor‐pressure measurements at 25, 37.5 and 50 °C for five dextran samples that differ in f, the fraction of randomly distributed charged monomer units. The function χ(φ) has a minimum that is shifted towards lower χ values as f increases. The higher the temperature, the more the individual curves fan out. The heats of dilution at high polymer concentrations change from exothermal to endothermal as f increases. The results can be well modeled by an approach accounting explicitly for chain connectivity and conformational changes. A smooth transition of the solution properties upon the random introduction of charged units into dextran is observed.magnified image