Pattern formation caused by double quenches in binary polymer mixtures: Response of phase-separated structure to a second quench within a two-phase region

Here we demonstrate the evolution of an unusual phase-separated pattern caused by a double quench: a first quench from a one-phase to a two-phase region and a subsequent second quench within the two-phase region. The resulting pattern evolution strongly depends upon the type of a double-quench sequence. A deeper second quench causes a level structure, while a shallower one causes a long-range interface instability coming from a mismatch in the local volume-surface ratio. The response of a domain structure to a second quench is qualitatively discussed on the basis of the phase diagram and existing theories for the coarsening dynamics of usual phase separation.