Molecular Dynamics Simulations of Molecular Diffusion Equilibrium and Breakdown Mechanism of Oil-Impregnated Pressboard with Water Impurity

Theoretical investigation of electronic, energetic, and mechanical properties of polyvinyl alcohol/cellulose composite hydrogel electrolyte

Hydrogels are a new class of electrolytic materials employed in zinc-air batteries due to their significant on the battery's performance. However, the effectiveness of electrolytic hydrogel is affected by factors such as water content, temperature, additives, etc. Using DMol3 and molecular dynamics modeling techniques, this research aimed at investigating the electronic properties, effect of water content, and temperature on the binding energy, cohesive energy, and the mechanical properties of polyvinyl alcohol/cellulose-based composite hydrogel at the molecular level. The electronic optimized structures of the polymeric materials and parameters such as frontier molecular orbitals, band gap and electron density were analyzed. The results revealed that the binding energies of hydrogel polymer composite increased as the number of water molecules in the composite increased up to 60 % after which the binding energy decreased. In addition, the temperature increase led to a decrease in the binding energy of the composite. The cohesive energy density of the composite was highest at 40 % water content while higher temperatures decreased the cohesive energy density of the hydrogel. As the number of water molecules increased from 29 to 256, the tensile modulus increased from 0.707 × 10-3 to 2.821 × 10-3 Gpa; while the bulk modulus (K) increased in the order of K 40 > 50 > 30 > 20 > 10 respectively. These results serve as a theoretical enlightenment and a guide for experimental works in the field of energy conversion and storage devices.

Development of an Ethanol-Free Salbutamol Sulfate Metered-Dose Inhaler: Application of Molecular Dynamic Simulation-based Prediction of Intermolecular Interaction

INTRODUCTION

More than fifty years after the commercialization of the Ventolin metered-dose inhaler (MDI), its constituent active ingredient, salbutamol sulfate (SS) remains the most prescribed short-acting beta agonist for the first-line treatment of acute asthma attacks and the metered-dose inhaler remains its primary dosage form. The first generation of Ventolin MDI was developed at a time when environmental and regulatory concerns were less stringent than today. The MDI industry is now on the verge of a second major reformulation effort in response to environmental concerns. This paper serves to illustrate how modern computational modeling of molecular interactions can aid the reformulation process. By way of a case study, computational modeling was performed to compare poly(ethylene glycol) 400 (PEG400) and, separately, isopropyl myristate (IPM) as substitutes for the ethanol used in some generic salbutamol sulfate suspension-based hydrofluoroalkane MDIs.

METHODS

PEG400 and isopropyl myristate (IPM) were investigated as potential alternative cosolvents to ethanol in HFA134a-based SS suspension MDI formulations. Density functional theory (DFT) molecular dynamics simulations were used to evaluate the compatibility of the candidate cosolvents with the formulation's components. Corresponding physical formulations were filled into polyethylene terephthalate (PET) and, separately, aluminium canisters. In-vitro pharmaceutical product performance and macroscopic visual appearance were assessed and compared to the results of the simulation studies.

RESULTS

The simulation studies indicated that PEG400 would be a good candidate as a replacement for ethanol whereas IPM would not. The in-vitro and visual assessments support the predicted outcome of the simulation studies.

CONCLUSION

This work suggests that molecular dynamics simulations may provide a useful tool to aid the selection of compatible excipients when reformulating MDI suspension-based products, thereby reducing the time and cost associated with manufacturing and testing of physical samples.

Simulation of Binodal and Spinodal Curves of Phase State Diagrams for Binary Polymer Systems

A new approach is proposed for simulating binodal and spinodal curves of phase diagrams for binary polymer systems. It is shown that the Flory–Huggins theory makes it possible to predict phase behavior in a wide range of temperatures and concentrations based on limited data on the components’ solubility. The approbation data of the technique are presented in the example of PS–PB and PS–PMMA systems, for which generalized phase diagrams are constructed.

Chemical computational approaches for optimization of effective surfactants in enhanced oil recovery

The surfactant flooding becomes an attractive method among several Enhanced Oil Recovery (EOR) processes to improve the recovery of residual oil left behind in the reservoir after secondary oil recovery process. The designing of a new effective surfactant is a comparatively complex and often time consuming process as well as cost-effective due to its dependency on the crude oil and reservoir properties. An alternative chemical computational approach is focused in this article to optimize the performance of effective surfactant system for EOR. The molecular dynamics (MD), dissipative particle dynamics (DPD) and density functional theory (DFT) simulations are mostly used chemical computational approaches to study the behaviour in multiple phase systems like surfactant/oil/brine. This article highlighted a review on the impact of surfactant head group structure on oil/water interfacial property like interfacial tensions, interface formation energy, interfacial thickness by MD simulation. The effect of entropy in micelle formation has also discussed through MD simulation. The polarity, dipole moment, charge distribution and molecular structure optimization have been illustrated by DFT. A relatively new coarse-grained method, DPD is also emphasized the phase behaviour of surfactant/oil/brine as well as polymer-surfactant complex system.