Simple and Accurate Calibration of the Flory-Huggins Interaction Parameter

Abstract

This work improves on a standard method used to calibrate χ, the Flory-Huggins interaction parameter, in experimental systems. The common method is to fit the order-disorder transition (ODT) of symmetric diblock copolymer melts to the mean-field prediction (χN)_{ODT} = 10.495. This work improves the calibration by using the more accurate prediction of (χN)_{ODT} from Morse and coworkers, correcting for the small degrees of polydispersity and compositional asymmetry that exist in real diblock copolymers. To find the correction, polydisperse lattice simulations are conducted over a wide range of invariant polymerization indices. The correction for compositional asymmetry is extracted from simulations for asymmetric diblocks conducted by Ghasimakbari and Morse. This improved calibration is demonstrated for 19 different chemistries, using previously published data from experiments. This calibration provides a considerable increase in accuracy, while still being simple to apply.