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Figure 6. A (left) Pressure - composition phase diagram. ^ lb and ^ ^ represent the coexistence phase compositions when pressure is reduced from Pi to Pf and the solutions phase separates into a polymer-lean and polymer-rich phase. B(right) Transient structure formation and evolution when the nucleation and growth (paths I and 111) and spinodal decomposition (path 11) regimes are entered.

Understanding the time scale of new phase formation and growth and devising methods to quench and pin a system in one of its non-equilibrium transient states are important considerations in producing micro-structured materials for example structures with specific pore size, distribution or morphologies. The system must be quenched in the appropriate time frame if the transient structures are to be locked-in. By documenting the kinetics of phase separation and mapping the experimentally accessible spinodal boundary, one could fine-tune the end-pressures of the quench to induce phase separation by nucleation and growth or spinodal decomposition, and try to capture the transient structures by matching the vitrification or gelation times with the time scale of the domain growth. For example, such an understanding would help develop methodologies for formation of co-continuous morphology development even from polymer solutions that may not be initially at the critical polymer concentration.

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