Thermodynamic, spectroscopic and DFT studies of binary mixtures of poly(vinylpyrrolidone) (PVP) with ethanol, 1-propanol and 1-butanol

Temperature Effect on the Corrosion Inhibition of Carbon Steel by Polymeric Ionic Liquids in Acid Medium

In the present research work, the temperature effect on the corrosion inhibition process of API 5L X60 steel in 1 M H2SO4 by employing three vinylimidazolium poly(ionic liquid)s (PILs) was studied by means of electrochemical techniques, surface analysis and computational simulation. The results revealed that the maximal inhibition efficiency (75%) was achieved by Poly[VIMC4][Im] at 308 K and 175 ppm. The PILs showed Ecorr displacements with respect to the blank from −14 mV to −31 mV, which revealed the behavior of mixed-type corrosion inhibitors (CIs). The steel micrographs, in the presence and absence of PILs, showed less surface damage in the presence of PILs, thus confirming their inhibiting effect. The computational studies of the molecular orbitals and molecular electrostatic potential of the monomers suggested that the formation of a protecting film could be mainly due to the nitrogen and oxygen heteroatoms present in each structure.

Impact of the solvent composition on the structural and mechanical properties of customizable electrospun poly(vinylpyrrolidone) fiber mats

The performance of fibrous membrane composites fabricated via electrospinning is strongly influenced by the solution's properties, process variables and ambient conditions, although a precise mechanism for controlling the properties of the resulting composite has remained elusive. In this work, we focus on the fabrication of electrospun poly(vinylpyrrolidone) (PVP) fibers, by varying both the polymer concentration and the mixture of ethanol (EtOH) and dimethylformamide (DMF) used as solvent. The impact of the solvent composition on the structural properties is assessed by a combined experimental and theoretical approach, employing scanning electron microscopy (SEM), differential scanning calorimetry (DSC), rheology, Fourier-transform infrared spectroscopy (FTIR) and stress-strain curves obtained from tensile tests to characterize the fibrous membranes produced, and density functional theory (DFT) calculations to explain the solvent's affect on PVP crystallization. We establish a morphological phase diagram, and propose a possible mechanism based on the measured fiber diameter distribution, the viscoelastic properties of the precursor solution, the correlation between the functional groups and the mechanical properties, the thermal transitions and the degree of crystallinity. We also employ DFT calculations to model the polymer coverage at equilibrium of a PVP polymer chain in the presence of EtOH/DMF solvent mixtures to corroborate the crucial role their O or -OH groups play in achieving high PVP coverages and promoting the stability of the resulting fiber. These findings will be valuable to researchers interested in predicting, modulating, and controlling both a fiber's morphology and its concomitant physico-chemical properties.