Ckt C o[1 Ac A TkeDk22

where C o is the amplitude of the correlation function of the light scattered when the polymer solution is in thermal equilibrium (A T = 0) and where Ac (A T,k) represents the enhancement of the amplitude due to the presence of a temperature gradient. As mentioned earlier, this enhancement is proportional to (AT)2 and inversely proportional to k 4:

In the case that k l AT, the coefficient A *c becomes [18]

In Eq. (4) v in the kinematic viscosity of the polymer solution, ^ the chemical potential difference between solvent and solute such that the derivative (6^/6w)p,T taken at constant pressure p and constant temperature T, is proportional to the inverse osmotic compressibility of thesolution.

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