Dr. Olivier Vitrac presents: An atomistic Flory-Huggins formulation for the tailored prediction of activity and partition coefficients
From Cimberly Weir
Abstract: Claiming that activity coefficients are the easiest properties to calculate was a utopia until few years ago. Conventional techniques sample configurational space by particle insertion/deletion methods or by thermodynamic integration ones. They are particularly time-consuming and almost intractable for large solutes in entangled polymer matrices. Conversely, we developed new tailored methods to estimate chemical potentials or activity coefficients in situations met in food packaging applications: aqueous dominant mixtures, homopolymers and copolymers. They rely on a compressible Flory-Huggins formulation at atomistic scale with additional entropy and enthalpy corrections inferred by molecular dynamics simulation. Corrections are particularly important to reproduce radial distributions, cooperative hydrogen bonding and the residual elastic energy in glassy polymers. The whole approach has been validated to estimate partition coefficients of various substances (e.g., aroma, plastic additives, homologous series of alkanes and alcohols) between a broad range of polymers and food simulants.