Numerical simulation of the self-assembly of a polymer-polymer-solvent ternary system on a heterogeneously functionalized substrate

The spinodal decomposition of a polymer-polymer-solvent ternary blend spin coated on heterogeneously functionalized substrate is studied in a three-dimensional numerical model. The Cahn-Hilliard equation was used to describe the free energy profile of the domain. The mechanism of the morphology evolution was studied quantitatively. The well-established linear relationship of the characteristic length, R(t), with t^1/3 can be observed in the simulation results. The functionalized substrate greatly affected the morphology evolution of blends with different solvent concentrations. The results indicated that a critical time can be observed, at which the evolution rate changes abruptly, also after which the compatibility of the surface morphology to the functionalized substrate pattern increases at a much lower pace in the diluted solution. In the condensed solution, the compatibility actually decreases beyond the critical time. The influence of solvent evaporation is investigated and a sharper interface was observed in the case with solvent evaporation and film thickness reduction.