Correlation length of a near-critical, eight-arm star polystyrene in methylcyclohexane

The turbidity of monodisperse, eight-arm star polystyrene in methylcyclohexane has been measured near each system's critical point and used to determine the correlation length amplitude $\xi _{0 }$at various molecular weights. The turbidity was determined from the measured ratio of the transmitted to incident light intensities as a function of temperature. Various systematic errors were explored and eliminated in obtaining a value of $\xi _{0}$ for each molecular weight of the branched polystyrene in methylcyclohexane. Ornstein-Zernike theory is used to fit the turbidity data. The values of $\xi _{0}$ and their dependence on molecular weight are comparable to that reported in the literature for a linear polystyrene of the same molecular weight in methylcyclohexane. We acknowledge the support from NSF-REU grant DMR 0243811 and to the donors of the American Chemical Society Petroleum Research Fund.