The Turbidity of an 8-arm Star Polystyrene in Methylcyclohexane Near the Critical Temperature

Christopher J. Locke

Measurements of the light intensity transmitted through a cell containing a mixture of a star polystyrene and methylcyclohexane (star-ps/myc) were made as a function of temperature. The turbidity was calculated from the transmitted light intensity data and turbidity was compared to the theoretical prediction of universal exponents υ and γ, for correlation length amplitude ξo, and for turbidity amplitude τo. The data were analyzed using a weighted nonlinear least squares routine with the critical exponents υ and γ held constant at the predicted values of 1.24 and 0.63, respectively. For a 0.155 mass fraction star-ps/mcy, the amplitude of correlation length ξo was determined to be 0.452±0.005 nm with a turbidity amplitude of τo = (84.8±0.6) x 10-6cm-1. For a 0.145 mass fraction star-ps/mcy, the amplitude of correlation length ξo was determined to be 0.597±0.005 nm and the turbidity amplitude to be τo = (107.4±0.7) x 10-6cm-1. These values of ξo are less than what has been measured for a linear polystyrene of the same Mw in methylcyclohexane.