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Tuning Structure and Rheology of Silica–Latex Nanocomposites with the Molecular Weight of Matrix Chains: A Coupled SAXS–TEM–Simulation Approach
journal contribution
posted on 2014-05-13, 00:00 authored by Amélie Banc, Anne-Caroline Genix, Mathieu Chirat, Christelle Dupas, Sylvain Caillol, Michael Sztucki, Julian OberdisseThe structure of silica–latex
nanocomposites of three matrix
chain masses (20, 50, and 160 kg/mol of poly(ethyl methacrylate))
are studied using a SAXS/TEM approach, coupled via Monte Carlo simulations
of scattering of fully polydisperse silica nanoparticle aggregates.
At low silica concentrations (1 vol. %), the impact of the matrix
chain mass on the structure is quantified in terms of the aggregation
number distribution function, highest mass leading to individual dispersion,
whereas the lower masses favor the formation of small aggregates.
Both simulations for SAXS and TEM give compatible aggregate compacities
around 10 vol. %, indicating that the construction algorithm for aggregates
is realistic. Our results on structure are rationalized in terms of
the critical collision time between nanoparticles due to diffusion
in viscous matrices. At higher concentrations, aggregates overlap
and form a percolated network, with a smaller and lighter mesh in
the presence of high mass polymers. The linear rheology is investigated
with oscillatory shear experiments. It shows a feature related to
the silica structure at low frequencies, the amplitude of which can
be described by two power laws separated by the percolation threshold
of aggregates.
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Monte Carlo simulationsMolecular Weighttermmasses favorconstruction algorithmTuning StructureSAXSMatrix Chainscollision timeaggregates overlaposcillatory shear experimentsTEMpercolated network10 volpower lawspercolation thresholdsilica structureaggregation number distribution functionconcentrationpolydisperse silica nanoparticle aggregatesmass polymersmatrix chain mass
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