The correlation length of an eight-arm polystyrene in methylcyclohexane near the critical point

Nithya L. Venkataraman, Christopher J. Locke, and D. T. Jacobs

The turbidity of eight-arm polystyrene in methylcyclohexane has been measured and used to determine the correlation length amplitude ξo. The turbidity in this system was determined from the measured ratio of the transmitted to incident light intensities over three decades in reduced temperature. Using Ornstein-Zernike theory, we are able to fit the turbidity data and determine that ξo = 0.604 ± 0.010 nm for this branched polystyrene with a total molecular weight of 74,000. This value of ξo is less than that reported in the literature for a linear polystyrene of the same molecular weight in methylcyclohexane. Support for this research was provided by the grants NSF 9987850 and NASA NAG8-1433.