New group contribution estimation of solvent activity in polymer solutions

A new group contribution method (GCM) approach, based upon the combination of a thermodynamic model and molecular simulation (MS) is introduced. While other conventional GCMs require fitting with experimental data to determine group parameter values, proposed model calculates them directly using the pairwise interaction energy of functional groups (FG), obtained from MS. The solvent activities of a large variety of polymer solutions were estimated using the Helmholtz energy of mixing, based on the modified double lattice (MDL) model. For each polymer/solvent system, the interaction energy term within the Helmholtz energy expression is determined using the aforementioned group parameter derived from MS combined GCM (MS–GCM). From a number of polymer and solvent molecules, eleven FGs are defined. As considering FG connectivity, dummy atoms are introduced at the first adjacent positions in order to prevent impossible configurations during interaction energy calculation. The molecule disassembling method and dummy atom selection for each FG are carefully investigated. Newly proposed approach of MS–GCM could reduce the number of parameter much less than conventional GCMs but successfully predicted solvent activity. Its total deviation average of solvent activity estimation is 3.9%. Although it is little bit higher than previous work of Hu et al. but still remains in acceptable level.