Correlation of binary interaction energies for polymer repeat unit pairs via connectivity indices

Departures from the geometric mean assumption for the interaction energy between unlike polymer repeat unit pairs i/j computed from experimental data, were correlated with the molecular connectivity indices for the repeat units. The effects of various factors on the correlation results were investigated. A better correlation is obtained when terms involving the solubility parameters for the repeat units are included. This empirical scheme provides a viable way to predict interaction energies, and, thus, blend phase behavior and interfacial parameters. The limitations of this scheme and possible ways to improve the correlation are discussed.