Poly(vinylpyrrolidone)-iodine (PVPI)-based materials have attracted significant attention, owing to their effective inhibition of COVID-19. However, the complexation and release manner of iodine in PVPI are not fully understood. This article reveals the role of halogen bonding in PVPI chemistry through a combination of experimental and computational approaches, including ultraviolet−visible spectroscopy, Fourier-transform infrared spectroscopy, Raman spectroscopy, electronic structure calculations, electronically excited-state analysis, electrostatic potential mapping on molecular van der Waals surfaces, halogen bond energy calculations, and thermodynamic equilibrium analysis. Our research shows that, in both the solid state and solution, PVPI contains iodine molecules bonded with carbonyl groups as well as polyiodides derived from the ionization and assembling of iodine molecules. The iodophors (i.e., PVP, iodide, and polyiodides) interact with iodine molecules through halogen bonds. The halogen bond energy is as low as 2−8 kcal/mol, enabling the easy release of iodine by the iodophors. In PVPI solutions, the complexation and release of iodine reach a chemical equilibrium that is susceptible to temperature and other iodophors. Raising the temperature favors the release of iodine. Some synthetic polymers, biological proteins, and phospholipids can extract iodine molecules from solutions of PVPI, demonstrating good iodophor abilities.

International audienceCubic equations of state (EoS) are widely used for the prediction of thermodynamic properties of petroleum fluids containing both well-defined and pseudo-components. Such EoS require as input parameters the critical temperature (T-c), the critical pressure (P-c), and the acentric factor (omega) of each compound. For well-defined components, such properties are known from experiments and easily obtained. For pseudo-components they are routinely estimated using one of the numerous characterization methods (CM) available in the open literature. A CM is nothing more than a set of correlations which makes it possible to estimate T-c, P-c, and omega of a pseudo-component (PC) from the knowledge of its normal boiling point (NBP), molecular weight (MW), or specific gravity (SG). Regarding the binary-interaction parameters (BIP) k(ij) (where i and/or j are/is a pseudo-component(s)) which appear in classical mixing rules, they are either set to zero or estimated by a specific correlation. Most of the proposed correlations are however purely empirical and usually only make possible the estimation of the k(ij) between light components (H2S, CO2, N-2, C-1, C-2, and C-3) and a pseudo-component. The full k(ij) matrix is thus beyond reach and the BIP are usually temperature-independent. In this work, the PPR78 model is used to predict BIP suitable for the PengRobinson EoS whereas the PR2SRK model is used to predict BIP suitable for any other cubic EoS. Since these models can be seen as group-contribution methods (GCM) to estimate the kij, one needs to access the chemical structure of each PC. The chemical structure of PC is however too complex to be precisely determined. For this reason, it was assumed that each PC was made of only three groups: C-PAR, C-NAP, and C-ARO in order to take into account their paraffinic, naphthenic, and aromatic characters, respectively. The occurrences (N) of the three aforementioned groups are determined from the knowledge of T-c,CM, P-c,(CM), and omega(CM) (issuing from a CM). To reach this goal, GC methods aimed at estimating T-c, P-c, and omega of hydrocarbons were developed. Such methods have the ability to consider only three elementary groups: C-PAR, C-NAP, and C-ARO. In the end, the three known properties (T-c,CM, P-c,(CM), and omega(CM)) can be expressed as functions of N-PAR, N-NAP, and N-ARO (the occurrences of the groups) and we thus only need to solve a system of three equations with three unknowns. To check its validity, the present approach is applied to the prediction of the phase behavior of real petroleum fluids containing pseudo-components. The test results show the pertinence of the proposed method to predict the k(ij) when i and/or j is a pseudo-component

The thermodynamics of alkyne-containing mixtures is fundamental to the petroleum and chemical industries. Such mixtures are made complex both by the quantity and the variety of the species present thus justifying the need for a predictive model capable of guesstimating energetic and phase-equilibrium mixture properties. In this respect, the E-PPR78 (enhanced-predictive 1978, Peng− Robinson equation of state) model appears as a suitable candidate since it combines the well-established Peng−Robinson equation of state and an original groupcontribution method making it possible to estimate the temperature-dependent binary interaction parameters, k ij (T), involved in the van der Waals one-fluid mixing rules. With the 37 groups defined in previous works, such a model could be used to predict fluid-phase equilibria and energetic properties of systems containing hydrocarbons, permanent gases (CO 2 , N 2 , H 2 S, H 2 , CO, He, Ar, SO 2 , O 2 , NO, COS, NH 3 , NO 2 /N 2 O 4 , N 2 O), mercaptans, fluoro-compounds, and water. In this study, three alkyne groups ("HCCH", "CCH", and "CC") are added in order to accurately predict phase-equilibrium properties and enthalpies of mixing of alkyne-containing multicomponent mixtures. The determination of the group-interaction parameters (involved in the k ij (T) expression) between two groups including at least one alkyne group is performed with the help of a comprehensive database of binary-system phaseequilibrium and mixing-enthalpy data.