Application of inverse gas chromatography to multicomponent polymer-solvent-solvent systems /

by 1979- Galdamez Pen?a, Jose? Roma?n

iii The application of a mass spectrometer detector in capillary column inverse gas chromatography is shown to be a valuable tool in the measurement of diffusion and solubility in polymer-solvent systems. The component specific detector, a mass spectrometer detector, provides excellent results for binary polymer-solvent systems, but it is particularly valuable because it can be readily applied to multicomponent systems. In this work a new inverse gas chromatograph (IGC) apparatus was developed combining a mass spectrometer detector with a traditional gas chromatograph. Results for a number of infinitely dilute solvents in poly(vinyl acetate) (PVAc) are reported over a range of temperature from 60 to 150°C to benchmark the unit. A good agreement with other IGC source was found. The use of a mass spectrometer detector allows one to obtain reliable results for experiments when a mixture of several components was injected into the column at infinite dilution. Results are also reported for finite concentrations of toluene and methanol in PVAc from 60 to 110°C. In addition, the technique was applied to study the effect of finite concentrations of toluene on the diffusion coefficients of THF and cyclohexane in PVAc. The experimental data compare well with literature values for both infinite and finite concentrations, indicating that the experimental protocol described in this work is sound. The study of true multicomponent systems in which the polymer was saturated with finite concentrations of two solvents was conducted. The experimental chromatographs consisted of two independent responses, one for each of the solvents. iv This allows one to compare these profiles with theoretical models to obtain the thermodynamic and transport properties. Two models were used to calculate solubility and diffusivity in ternary mixtures: a binary model that was used to fit independently each of the two elution profiles and a ternary model which fits simultaneously both peaks in a ternary experiment. The results are promising showing good agreement for solubility with prediction obtained from the UNIFAC-FV theory for ternary systems. Some discrepancies between the experimental data and the prediction were found at higher solvent concentrations, where some of the model’s assumptions break down. The main diffusion coefficients for toluene and THF were obtained in the ternary systems. No important differences were found in diffusivity and solubility between the models. The diffusion coefficients were found to follow the expected trend with composition. This work provides the theoretical and experimental basis to analyze the complex multicomponent systems from a practical point of view, and for the first time in inverse gas chromatography it can be used to obtain diffusivity information.