Even three decades after signing the Chemical Weapons Convention, organophosphorus chemical warfare agents (CWAs), such as sarin, remain a threat. The development of novel methods for the detection of CWAs, protection from CWAs, and CWA decontamination motivates research on their physicochemical properties. Due to the extreme toxicity of sarin, most of the experimental studies are carried out using less toxic simulant compounds. In addition to experimental studies of sarin simulants, both sarin and simulants can be studied using in silico experimentsmolecular simulations. The results of classical molecular modeling of the compounds and their agreement with experimental data rely on the force field used to describe the system. In recent years, there have been several force fields proposed for sarin and its most common simulant dimethyl methylphosphonate (DMMP). However, other simulants frequently used in experiments received less attention from the molecular simulation perspective, for example, to date, there is no force field and no simulation data for diisopropyl methylphosphonate (DIMP). Here, we compare the literature force fields for sarin and DMMP, focusing specifically on the vapor–liquid equilibrium for the pure species. We carried out Monte Carlo and molecular dynamics simulations using the existing literature force fields from which we predicted the liquid densities and vapor pressures developing the entire binodal curves. We compared the predictions to the experimental data and showed that the TraPPE-UA force field outperformed the other force fields. Thus, we extended TraPPE-UA for DIMP, utilized this force field in molecular simulations, and predicted the liquid densities and vapor pressures for a range of temperatures (binodal curve), which agreed well with the published experimental data. From the binodal, we calculated the critical properties of DIMP and demonstrated that these parameters can be used in the Peng–Robinson equation of state for this compound.

The development of effective protection against exposure to chemical warfare agents (CWAs), such as sarin, relies on studies of its adsorption on the capturing materials and seeking candidates capable of adsorbing large amounts of sarin gas. Many metal−organic frameworks (MOFs) are promising materials for the effective capture and degradation of sarin and simulant substances. Among the simulants capable of mimicking thermodynamic properties of the agent, not all of them have been investigated on the ability to act similarly in the adsorption process, in particular, whether the agent and a simulant have similar mechanisms of binding to the MOF surface. Molecular simulation studies not only provide a safe way to investigate the aforementioned processes but can also help reveal the mechanisms of interactions between the adsorbents and the adsorbing compounds at the molecular level. We performed Monte Carlo simulations of the adsorption of sarin and three simulants, dimethyl methylphosphonate (DMMP), diisopropyl methylphosphonate (DIMP), and diisopropyl fluorophosphate (DIFP), on selected MOFs that have previously shown strong capabilities to adsorb sarin. On the basis of the calculated adsorption isotherms, enthalpy of adsorption, and radial distribution functions, we revealed common mechanisms among the particularly efficient adsorbents as well as the ability of simulants to mimic them. The findings can help in selecting a suitable simulant compound to study CWA adsorption on MOFs and guide further synthesis of efficient MOFs for the capture of organophosphorus compounds.

The paper presents a theoretical approach for describing the influence of an electric field on the conformation of an electrically neutral dielectric polymer chain dissolved in a dielectric solvent with an admixture of a target compound. Each monomer and each molecule of the target compound carries positive excess polarizability and the solvent is described as a continuous dielectric medium. The model is based on the Flory-type mean-field theory. We demonstrate non-monotonic dependences of the expansion factor and the concentration of the target compound on the strength of the electric field and molecular polarizability. Namely, the target compound concentration in the internal polymer volume as a function of electric field strength has pronounced maxima if the molecules are polarizable. In addition, the expansion factor of the non-polarizable polymer chain can be controlled by the electric field. The dependences of the expansion factor and target compound concentration on the monomer polarizability exhibit minima and intersection points. The intersection points correspond to the equality of dielectric permittivities in the bulk solution and in the internal polymer volume.

Correction for 'Statistical theory of polarizable target compound impregnation into a polymer coil under the influence of an electric field' by A. L. Kolesnikov et al., Soft Matter, 2017, DOI: 10.1039/c7sm00417f.