Divergence of the structure function observations by light scattering

2 Divergence of the structure function. Observations by light scattering 

Numerous light-scattering experiments have been performed with polymer solutions in the vicinity of the critical demixtion point in order to determine the structure function fi(q). 

Experimental values of 1 /I(q) obtained8 for the same sample at various temperatures are plotted in Fig. 16.8 against q1. The sample is a polystyrene (Afw = 1.1 x 10s) solution in cyclohexane. The volume fraction of polystyrene is cp = 0.0813 

For T — 7 (q ) 1, the measured intensities are nearly independent of the transfer wave number q. This result can be understood as follows the inverse scattering intensity (16.4.27) reads 

The condition q2 °Rq 1 is quite well verified in the experimental situation corresponding to Fig. 16.8. In fact, the value °Rq of the mean square radius of gyration of a Brownian chain of molecular mass Afw = 1.1 x 10s is 

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