Prediction of a Broad Spectra of Membrane Morphologies Through a New NIPS Thermo-Kinetic Model

Abstract

This work presents a novel semiempirical mathematical approach consisting of a coupled thermo-kinetic model as valuable tool for predicting the polymeric fraction profile of membranes synthesized by nonsolvent induced phase separation (NIPS). Equilibrium binodal curves (BCs) of the system component were incorporated to the Fick’s diffusive kinetic model allowing a satisfactory prediction of the tendency to develop symmetric or asymmetric porous membrane morphologies, as well as a fair quantification of average porous fraction profiles. The model was validated using two different ternary systems: (i) polycaprolactone (PCL)/N-methylpyrrolidone (NMP)/water (W) characteristic of instantaneous demixing (asymmetric finger-like porous cross-section morphology); and (ii) PCL/NMP/isopropanol (IPA) characteristic of delayed demixing (symmetric sponge-like cross-section morphology). The loading of graphene oxide (GO) in the quaternary system PCL/GO/NMP/IPA also gave rise to a sponge-like porosity, characteristic of delayed demixing systems, which was reasonably predicted by the coupled thermo-kinetic model developed in this study. In addition, a computational scanning electron microscopy (SEM) image processing methodology was developed to validate the thermo-kinetic model, resulting in an advantageous tool for that purpose. Overall, this work reveals the usefulness of the new thermo-kinetic mathematical approach as a facile computational tool for membrane manufacturers and researchers for a preliminary discrimination of component combinations in quaternary polymer/nanofiller/solvent/nonsolvent NIPS systems.