An efficient method for prediction of the vapor−liquid and liquid−liquid phase behaviors of polymer−solvent mixtures is proposed using the COSMO-SAC activity coefficient model. In particular, we examine various approaches for generating the screening charge distribution of homepolymers and copolymers from quantum mechanical calculations and propose a novel method to generate such data efficiently using a finite number of repeating units. The free volume effects known to be important in polymer solutions are considered through the free volume model of Elbro and co-workers. We have examined this model using 2249 vapor−liquid equilibria data points from 25 homopolymers, 8 copolymers, and 48 solvents. The overall average deviation (AAD%) of solvent activity is found to be about 16%, which is comparable to that from other UNIFAC-based models. The liquid−liquid equilibrium of polymer−solvent mixtures can be predicted in qualitative agreement with experiment. The proposed method is capable of describing the changes in solvent activity due to temperature, polymer molecular weight, and polymer tacticity. Our results suggest that the proposed method is a useful complementary to group contribution method for phase behavior of polymer solutions when group parameter or density information of polymers is unavailable.

Increasing atmospheric CO 2 concentration and dwindling fossil fuel supply necessitate the search for efficient methods for CO 2 conversion to fuels. Assorted studies have shown pyridine and its derivatives capable of (photo)electrochemically reducing CO 2 to methanol, and some mechanistic interpretations have been proposed. Here, we analyze the thermodynamic and kinetic aspects of the efficacy of pyridines as hydride-donating catalytic reagents that transfer hydrides via their dihydropyridinic form. We investigate both the effects of functionalizing pyridinic derivatives with electrondonating and electron-withdrawing groups on hydride-transfer catalyst strength, assessed via their hydricity (thermodynamic ability) and nucleophilicity (kinetic ability), and catalyst recyclability, assessed via their reduction potential. We find that pyridines substituted with electron-donating groups have stronger hydride-donating ability (having lower hydricity and larger nucleophilicity values), but are less efficiently recycled (having more negative reduction potentials). In contrast, pyridines substituted with electron-withdrawing groups are more efficiently recycled, but are weaker hydride donors. Functional group modification favorably tunes hydride strength or efficiency, but not both. We attribute this problematic coupling between the strength and recyclability of pyridinic hydrides to their aromatic nature and suggest several avenues for overcoming this difficulty.

Abstract:The liquid-liquid equilibrium (LLE) phase boundaries were determined experimentally for the ternary systems containing refined sunflower oil, methanol, and one of ten potential cosolvents at 308.2 K under atmospheric pressure by using cloud point method. n-Butylamine was found to be one of the best cosolvents, which could substantially enhance the miscibility between the oil and methanol. The LLE measurements were then extended to the ternary systems of methanol + refined sunflower oil, soybean oil, or canola oil in the presence of the auxiliary cosolvent n-butylamine at temperatures from 298.2 K to 318.2 K. The LLE data were utilized for estimating the model parameters of the NRTL and the UNIQUAC, respectively. In general, these two models can reasonably represent the LLE phase boundaries.

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