Optical theta conditions

The critical concentration of demixing was determined for 3 mixtures of polymers PS-PMMA, PS-PDMS and PS-PVAc at constant composition y = dCrp -0.5. The solvents used for the PS-PDMS couple were toluene, in which the "optical theta" condition was verified Anps = - AnpDMS and THF, in which the PDMS was matched AnpDMS = The system PS-PMMA was mixed in benzene where AnpMMA is 0. 

L. Giebel, M. Benmouna, R. Borsali, and E. W. Fischer. Quasielastic light scattering from polydimethylsiloxane/polymethyl methacrylate/chloroform under the optical theta condition. Macromolecules, 26 (1993), 2433-2438. 

Note that (0) = 0. The condition of the zero average differential refractive index is sometimes called optical theta. 

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