Spontaneous structure formation in polymer blends: implications for reactor design*

When engineering new materials for energy storage and membrane applications, material scientists must learn to design and create novel porous structures. A physical understanding of the relevant continuous manufacturing techniques is difficult to capture, particularly as micro-scale structure formation can be disrupted by the presence of macro-scale flows. Comprehensive modelling of such systems remains a challenge due to length scale disparity: any included transport models must be solved at the unit-operation scale, while simultaneously capturing structure formation at the level of the product material. Here, we simulate spontaneous structure formation within flowing polymer blends. Detailed pattern formation is modelled via a coupling of the Navier–Stokes and multi-component Cahn–Hilliard equations. To cascade physical information across scales, we consider a moving frame formation in which characteristic time-dependent shear fields are sampled from accompanying reactor-scale flow simulations. This approach enables a closed-loop design whereby macro-scale design parameters, including reactor geometry, can be tuned such that micro-scale properties are optimised for each target application.