A series of multibranched block copolymers was synthesized by means of anionic ring opening polymerization (AROP) techniques, using different alkoxide salts obtained from molecules that present different numbers of alcohol functions as initiators. Propylene oxide (PO) and ethylene oxide (EO) were polymerized in two steps, with the intent of obtaining multibranched block copolymers (PO/EO) with demulsifying activity in petroleum. The characterization of the polymers was done by means of size exclusion chromatography (SEC), Fourier transformed infrared spectroscopy (FTIR), carbon-13 nuclear magnetic resonance ( 13 C NMR), and thermogravimetric analysis (TGA). A theoretical study by semiempirical AM1/NDDO has been carried out in order to explain the growth of multiple branches from the initiators during the early stages of the anionic polymerization. These simulations revealed complex patterns of polymer growth and increasing polydispersities when initiators with a greater number of active sites were employed to start the reactions. Afterward, the water removal efficiency, as a function of the number of copolymer branches, was evaluated through bottle tests in two crude oils: a heavy crude oil with 12.71°API and an extra-heavy crude oil with 9.68°API, with a water content of 47 and 39 vol %, respectively. A complex and nonlinear behavior of the water removal, as a function of the number of the block copolymer branches, was observed.

An equation of state has been developed to describe the thermodynamic properties of single electrolytes in water over a wide range of temperatures from 25 °C to near the critical point of the solvent. The new equation of state was obtained from an analytical expression of the Helmholtz free energy containing three major contributions: (1) a discrete solvent term to account for the short-range interactions between uncharged particles based on the Peng−Robinson equation of state, (2) an ioncharging term described by the continuum-solvent model of Born, and (3) a charge−charge interaction term given by the explicit mean-spherical-approximation (MSA) expression. The thermodynamic model proposed here incorporates the chemical equilibrium of the dissolved electrolyte, allowing for the calculation of the corresponding degree of dissociation of the salt at different temperatures. The present equation of state was applied to the representation of the mean ionic activity coefficients, osmotic coefficients, standard free energies of ion hydration, and densities for NaCl, CaCl 2 , K 2 SO 4 , and MgSO 4 salts in water over a wide range of temperatures and salt molalities. The results indicate good agreement between the experimental data and the calculations generated from the present equation of state.

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The release of tetradecane from a multiple emulsion of the type tetradecane/water/hexadecane was studied experimentally using the differential scanning calorimetry technique. The kinetics of the tetradecane release was measured for three formulations containing different concentrations of hydrophilic surfactant (2%, 4%, and 7%). A new mass transfer model derived from the shrinking core model was developed. The values of the model parameters deduced from the least-squares fittings led to the determination of the tetradecane diffusivity. Thus, the preponderant mechanism of mass transfer was proved to be micellar diffusion and not molecular diffusion. This conclusion was confirmed by considering the effect of the change in the hydrophilic surfactant concentration.