Isorefractive scattering method

In recent years, Du of polystyrene has been measured by this isorefiac-tive scattering method [37-44]. The isorefractive solutions chosen were poly (methyl methacrylate) (PMMA) + benzene, poly(vinylmethylether) (PVME) + ortho-fluorotoluene (oFT), and PVME + toluene. In this section, we refer to a detailed study of Wheeler et al. [43] with PVME + oFT. 

Quasielashc light scattering was considered in detail in Chapter 4. The discussion here starts where Chapter 4 left off. The optical probe method refers to the special case of measurements on a ternary solvent matrix polymer rigid probe system in which the matrix polymer does not scatter significantly, while the probe species dominates scattering from the system even though it is dilute. Optical probe studies are formally similar to QELSS studies of ternary polymer polymer solvent systems containing an isorefractive polymer solvent pair. 

The determination of molar masses by non-colligative methods such as light scattering and ultracentrifugation will lead only to apparent molar masses if solvent mixtures are used whose components are not isorefractive. The observed increases or decreases of these apparent molar masses depend in sign and magnitude on both the preferential solvation and the refractive index inerement... 

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