The effect of relative humidity on the morphology of electrospun fibers of poly(vinyl alcohol), poly(methyl methacrylate), poly(vinyl chloride), polystyrene, and poly(lactic acid) dissolved in solvents such as toluene, N,N-dimethylformamide, 2,2,2-trifluoroethanol, and deionized water was studied by scanning electron microscopy to investigate the factors that may contribute to pore formation. Results showed that the presence of pores depends on factors such as the type of polymers used, the polymer–solvent combination, molecular weight, and the size of the electrospun structure. The final morphology developed implies a competition between the dynamics of phase separation and the rate of solvent evaporation. In addition, continuous solvent evaporation and constant stretching owing to the electric potential difference give rise to the final shape of porous electrospun fibers.Key words: electrospinning, relative humidity, porous fibers, polymers.

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The evaluation of the potential for separation of aqueous ethanol mixtures by liquid−liquid solvent extraction has been complicated by inconsistent results and differing experimental methodologies among researchers developing distribution coefficient data. A screening method for measuring equilibrium distribution coefficients for solvent extraction of ethanol from dilute aqueous solutions is presented to minimize potential sources of variation. These include entrainment, incomplete equilibration, impurities, and temperature changes during the preparation of samples for analysis. Multiple literature sources of data exist for each of 10 solvents. Results for these 10 solvents are compared among sources and to results generated from this method. The method also has general utility for the screening of solvents for extraction of other useful fermentation products.

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