| Abstract
| - Contrast variation small-angle neutron scattering (SANS) has been employed to study complex fluids comprisingmodel microemulsions and polymers. The systems are water-in-oil microemulsions with added non-adsorbing polymer,under good polymer solvency conditions and semidilute polymer concentrations. The polymer/colloid size ratio wasq ≈ 11, which is well within the “protein limit”. Four scattering contrasts were produced by selective deuteration ofthe dispersed and continuous phases and also the surfactant. In this way, the separate partial structure factors (PSF)for colloid−colloid (c−c), polymer−polymer (p−p), and colloid−polymer (c-p) have been obtained. The c−c PSFhas been compared with theoretical predictions, allowing determination of a polymer correlation length. This iscompared with a similar correlation length obtained from the p−p PSF, which is shown to increase with colloidconcentration. In this sense, adding microemulsion has a similar effect on the dissolved polymer as reducing the solventquality, and an effective Flory−Huggins χ parameter has been calculated. The cross-term PSF shows a distinctanti-correlation. This is the first time such structure factors have been determined experimentally for colloid−polymersystems in the protein limit and these allow a more detailed understanding of the structural interactions in thesesystems.
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