Comprehensive analysis of structural, dynamic, and thermodynamic properties of oil-in-water microemulsions coated with polyethylene oxide-decorated telechelic polymers and stabilized by non-ionic surfactants

Abstract

Molecular dynamics simulations are used to study the structural, dynamic and thermodynamic of properties neutral oil-in-water microemulsion particles coated with a telechelic steric polymer, polyethylene oxide-$C_{12}$$H_{25}$ (PEO-D) at different ϕ volume fractions. The microemulsion particles are stabilised by a non-ionic surfactant Triton $X_{100}$ ($T{X}_{100}$) and a co-surfactant Triton $X_{35}$ ($T{X}_{35}$). We graft a telechelic polymer PEO-D, onto the surface of the $T{X}_{100}$ microemulsion particles, the number of polymers on a microemulsion being denoted by n(PEO-D), where n is between 0 and 26.9. The total potential of a $T{X}_{100}$ microemulsion system is composed of a hard sphere potential, a Van der Waals potential and a Yukawa-type repulsive potential introduced by the surfactants. For a system of $T{X}_{100}$ microemulsion particles coated with PEO-D polymer, a steric repulsion potential is added to the total potential. The structural and thermodynamic properties and interactions between the microemulsions are determined using the correlation function g(r), the structure factor S(q) and the osmotic compressibility ${\chi }_T$. These properties show that increasing the volume fraction ϕ and adding the PEO-D polymer enhances the repulsive interactions. The dynamic properties are analysed using the mean square displacement MSD, the diffusion coefficient D, the viscosity η and the velocity autocorrelation function VACF. The dynamic results show that as the volume fraction or number of PEO-D polymers on each $T{X}_{100}$ microemulsion particle increases, the particle dynamics become increasingly complex and the system becomes highly viscous.