TRICRITICAL PHENOMENA IN BIMODAL POLYMER-SOLUTIONS .2. TURBIDITY MEASUREMENTS IN THE 3-PHASE REGION

The turbidites of four bimodal mixtures of polystyrene in methylcyclohexane have been measured in the three-phase region near the tricritical point. The results from eight different wave-lengths have been analyzed to obtain the correlation lengths xi and the susceptibilities chi. chi and xi are strongly correlated, so it is their ratio chi/xi that is determined most precisely. As the tricritical point is approached, all three quantities diverge, as expected from the classical mean-field theory. Although the uncertainities are larger than wished for, it appears that the Griffiths first sums get increasingly larger as the tricritical point is approached, and probably diverge in the same way as has been observed for other tricritical systems.