We propose here an alternative way to understand the characteristic pattern formation found in the so-called viscoelastic phase separations. Since the viscoelastic phase separations have been observed in systems with strong viscoelastic nature such as polymer solutions, numerical modelings for them have been conducted so far by introducing dynamic properties such as concentration-dependent mobility or elastic relaxation moduli to a usual scheme of phase separations. In contrast to these approaches, we propose the introduction of a small change, a bump, in the local free-energy function, keeping a parameter representing dynamic properties constant. We show that the bump in the local free-energy function successfully induces desired pattern formations in a controlled way, while it does not change equilibrium states. The mechanisms by which this free-energy approach reproduces experimentally observed pattern formations are discussed.
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