Temperature (K) Temperature (K)

Figure 4. Critical Demixing isopleths for PS/methylcyclohexane/n-heptane solutions. Parts "b'' and "c" show the diagrams in the vicinity of the hypercritical (homogeneous double critical) points. Modified from ref. 4 and used with permission.

the poorer solvent, /ra¬ęs-1-4-DMCH, but with Mw carefully chosen to properly size the one phase homogeneous region. For PS9x105 Thyp l lies slightly above 200 MPa but for this solution Phypl<0. Therefore MW was decreased slightly to yield Thypl for (PS5.75x105(7wt%)/trans-1,4-DMCH) at 175 MPa and 349.15 K. For this solution PHYPLlies at P=1.65MPa, 438.7K. This set of measurements establishes that the proposed master curve exists in at least one weakly interacting binary polymer solution (see Figure 5).

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