The vapor pressure of a binary polymer solution is determined by the activity of the solvent A, aA. Solvent activities in polymer solutions are measured either by the isopiestic method applying a reference system whose solvent activity is precisely known or by determining the solvent partial pressure, PA, and calculating the activity of the solvent by equation (1):
<math xmlns= "http://www.w3.org/1998/Math/MathML"><mrow><msub><mtext>a</mtext><mtext>A</mtext></msub><mtext>=</mtext><mrow><mo>(</mo><mrow><msub><mi>P</mi><mtext>A</mtext></msub><mtext>/</mtext><msubsup><mi>P</mi><mtext>A</mtext><mtext>s</mtext></msubsup></mrow><mo>)</mo></mrow><mtext>exp</mtext><mrow><mo>[</mo><mrow><mfrac><mrow><mrow><mo>(</mo><mrow><msub><mi>B</mi><mrow><mtext>AA</mtext></mrow></msub><mtext>–</mtext><mi>V</mi><mmultiscripts><mrow></mrow><mprescripts/><mtext>A</mtext><mtext>L</mtext></mmultiscripts></mrow><mo>)</mo></mrow><mrow><mo>(</mo><mrow><mi>P</mi><mo>–</mo><msubsup><mi>P</mi><mtext>A</mtext><mtext>s</mtext></msubsup></mrow><mo>)</mo></mrow></mrow><mrow><mi>R</mi><mi>T</mi></mrow></mfrac></mrow><mo>]</mo></mrow></mrow></math> (1)
where BAA is the second virial coefficient, PAs is the saturation vapor pressure, and VAL is the molar volume of the pure solvent A at the measuring temperature T. The exponential term is neglected in quite a lot of original papers, however, and only the reduced vapor pressures are given (such data are indicated by an asterisk in the table below). Vapor pressures of polymer solutions have been measured since the 1940s, but the amount of experimental data for polymer solutions is still relatively small in comparison to low-molecular mixtures and solutions. The data scatter with respect to temperature, concentration, molar mass, and other polymer characterization variables. Furthermore, the concentration range for measuring vapor pressures in good thermodynamic quality is often limited to the polymer mass fraction range between 0.4 and 0.85. A recent review on methods for the measurement of vapor pressures/solvent activities of polymer solutions and on related problems is given in Ref.1. Experimental data have been collected in several books Refs. 2-6.
The table below provides data for a number of polymer solutions as smoothed values over the complete range of solvent activities between 0 (polymer mass fraction = 1) and 1 (polymer mass fraction = 0). For this purpose, the data were selected from data books Refs. 4-6 as well as from a number of original sources Refs. 7-22, which are not included in these books. The appropriate data were smoothed. The final table provides the polymer mass fractions at given fixed solvent activities between 0.1 and 0.9. Of course, the user must keep in mind that the activity vs. concentration range of the experimental data is sometimes smaller than the complete range given below, thus the smoothed data should be used with sufficient care.
Generally, vapor pressures or solvent activities of binary polymer solutions depend on molar mass. However, for high molecular weight polymers (well above the oligomer region), this molar-mass dependence can be neglected in many cases. Therefore, the table below presents only data for polymer solutions where the number average molar mass Mn is in the order of 105 g/mol or even higher; therefore, the molar mass is not specified. The temperature is stated, even though the temperature dependence of aA is relatively small for the temperature ranges where most of the experimental data exist.
Polymer/Solvent | T/K | 0.1 | 0.2 | 0.3 | 0.4 | 0.5 | 0.6 | 0.7 | 0.8 | 0.9 |
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Acrylonitrile/Styrene Copolymer (28 wt% Acrylonitrile) | ||||||||||
Benzene * | 343.15 | 0.982 | 0.962 | 0.940 | 0.915 | 0.886 | 0.851 | 0.809 | 0.753 | 0.670 |
1,2-Dimethylbenzene * | 398.15 | 0.983 | 0.964 | 0.942 | 0.918 | 0.890 | 0.857 | 0.817 | 0.764 | 0.685 |
1,3-Dimethylbenzene * | 398.15 | 0.983 | 0.965 | 0.944 | 0.921 | 0.893 | 0.861 | 0.821 | 0.769 | 0.690 |
1,4-Dimethylbenzene * | 398.15 | 0.983 | 0.964 | 0.942 | 0.918 | 0.890 | 0.857 | 0.817 | 0.763 | 0.684 |
Propylbenzene * | 398.15 | 0.987 | 0.972 | 0.955 | 0.935 | 0.913 | 0.885 | 0.851 | 0.804 | 0.732 |
Toluene * | 343.15 | 0.982 | 0.962 | 0.940 | 0.915 | 0.886 | 0.851 | 0.809 | 0.753 | 0.669 |
Butadiene/Styrene Copolymer (41 wt% Styrene) | ||||||||||
Benzene * | 343.15 | 0.968 | 0.934 | 0.896 | 0.853 | 0.805 | 0.748 | 0.680 | 0.591 | 0.461 |
Cyclohexane * | 343.15 | 0.978 | 0.953 | 0.925 | 0.893 | 0.856 | 0.811 | 0.754 | 0.678 | 0.556 |
Ethylbenzene * | 398.15 | 0.974 | 0.945 | 0.912 | 0.875 | 0.831 | 0.779 | 0.713 | 0.625 | 0.491 |
Mesitylene * | 398.15 | 0.977 | 0.950 | 0.921 | 0.887 | 0.847 | 0.799 | 0.738 | 0.656 | 0.526 |
Toluene * | 343.15 | 0.970 | 0.936 | 0.899 | 0.857 | 0.808 | 0.751 | 0.682 | 0.591 | 0.456 |
Cellulose Triacetate | ||||||||||
Dichloromethane | 298.15 | 0.979 | 0.956 | 0.930 | 0.899 | 0.863 | 0.819 | 0.762 | 0.683 | 0.554 |
Trichloromethane | 298.15 | 0.978 | 0.953 | 0.924 | 0.892 | 0.853 | 0.806 | 0.747 | 0.665 | 0.533 |
Dextran | ||||||||||
Water | 313.15 | 0.988 | 0.975 | 0.960 | 0.942 | 0.921 | 0.894 | 0.860 | 0.810 | 0.725 |
Hydroxyethylcellulose | ||||||||||
Water | 368.15 | 0.988 | 0.974 | 0.958 | 0.939 | 0.915 | 0.884 | 0.841 | 0.775 | 0.650 |
Hydroxypropylstarch | ||||||||||
Water | 293.15 | 0.989 | 0.977 | 0.963 | 0.947 | 0.927 | 0.903 | 0.872 | 0.827 | 0.749 |
Nitrocellulose | ||||||||||
Ethyl acetate | 293.15 | 0.938 | 0.885 | 0.835 | 0.786 | 0.737 | 0.685 | 0.627 | 0.560 | 0.471 |
Ethyl formate | 293.15 | 0.958 | 0.916 | 0.873 | 0.828 | 0.780 | 0.728 | 0.668 | 0.595 | 0.494 |
Ethyl propionate | 293.15 | 0.941 | 0.889 | 0.839 | 0.789 | 0.739 | 0.685 | 0.625 | 0.555 | 0.460 |
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