We studied interaction of hydrophilic polymer chain
and hydrophilic silica nanoparticles in a dilute aqueous system
using an idealized model system comprised of a well characterized
polyvinyl alcohol of 100 Å Rg
and
hard spherical LUDOX® silica
of 80 Å radii. Interaction among the polymer chains forming
polymer clusters with collective polymer structure
factor induced by the polymer-mediated potentials of mean force
between the nanoparticles, was observed. However, Gaussian nature
of individual polymer chain remains unaltered. The dilute system
of polymer with low silica volume fraction has the scattering
form which was appropriately modeled as the sum of the individual
profiles of spherical silica particles and polymer cluster of
interchain
packing.
With increasing silica volume fraction in the dilute solution,
the spatial range parameter between the particles
is reduced; hence there is a net increase in the mean potential
force and consequently to stronger interaction between the silica
and polymer. In the dilute systems of high silica with low polymer
volume fraction, the polymer chain apparently attracted closer
to the silica and concurrently absorbed to the silica hard surface
and their scattering data were excellently fit with a model form
factor as comprising of one unit forming the core of the spherical
silica particles and the interacting polymer as the corona. This
result of severe change in polymer interchain
conformation
in a dilute system corroborated with reduced polymer
viscosity observed.