AbstractThe Flory‐Huggins interaction parameterχis determined as a function of volume fraction of polymerφby vapor‐pressure measurements at 25, 37.5 and 50 °C for five dextran samples that differ inf, the fraction of randomly distributed charged monomer units. The functionχ(φ) has a minimum that is shifted towards lowerχvalues asfincreases. The higher the temperature, the more the individual curves fan out. The heats of dilution at high polymer concentrations change from exothermal to endothermal asfincreases. 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