Aqueous mixtures of spherical and rodlike (flexible) macroparticles: structure and dynamics of latex spheres in saltfree solutions |
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Authors: | J Biegel C Hundegger B Nadig R Weber |
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Institution: | Fakult?t für Physik, Universit?t Konstanz, 78457, Konstanz, Germany
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Abstract: | This paper resumes light scattering investigations of saltfree aqueous solutions of two component mixtures of charged spheres
by extending those measurements to systems in which one component is replaced by essentially stiff rodlike particles. In a
second step of investigations these were replaced by linear flexible particles. Fd-virus particles (length l=883 nm) or macromolecules of NaPSS of four different contour lengths have been used as representatives. Mostly the concentration
of latex spheres was fixed at 0.02 Vol%. The concentration of the other component was varied over a wide range. Concerning
the scattering intensity, the contribution of the latex spheres dominates, in particular in the systems containing NaPSS particles.
This simplifies the interpretation of data considerably. A rearrangement of the spheres is observed, depending on the shape
of the other sort of particles. These conclusions can be drawn from the shift of measured static structure factor with concentration c. A power law is found for the q-value of the maximum. The exponent depends on the properties of the second component. For the lower molecular weight (MW)
samples of NaPSS below a critical concentration, the exponent is smaller than 1/3, decreasing the more the smaller the MW
of the samples is. A tentative explanation in terms of charge number of NaPSS particles is given. The short time dynamics
has been explored too. From the data a “dynamically determined structure factor” can be derived, that can be compared with
the measured static structure factor. Good (fd) and fair (NaPSS) agreement is obtained respectively. Only at small wavenumbers
below the maximum of deviations occur which increase with concentration; they are consistent with hydrodynamic interaction.
Received 30 July 1998 and Received in final form 14 December 1998 |
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Keywords: | PACS 61 25 Hq Macromolecular and polymer solutions polymer melts swelling - 78 35 +c Brillouin and Rayleigh scattering other light scattering - 83 70 Hq Heterogeneous liquids: suspensions dispersions emulsions pastes slurries foams block copolymers etc |
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