Symmetric tricritical point in a living polymer solution

We present a phase diagram styrene in chemical equilibrium with polystyrene, in solution in cyclohexane. We observe an upper critical solution point. Within our experimental error, the polymerization line meets the upper critical solution point. Both branches of the coexistence curve are consistent with a critical exponent as expected for a symmetric tricritical point. The unpolymerized branch shows the discontinuity in slope with the polymerization line which is expected for a nonclassical symmetric tricritical point. © 1990 The American Physical Society.

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