Elasticity and dynamics of particle gels in non-Newtonian melts |
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Authors: | Giovanni Romeo Giovanni Filippone Alberto Fernández-Nieves Pietro Russo Domenico Acierno |
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Institution: | (1) Department of Materials Engineering and Production, University of Napoli Federico II, P.le Tecchio, 80, 80125 Naples, Italy;(2) School of Physics, Georgia Institute of Technology, Atlanta, GA 30332, USA;(3) Institute of Chemistry and Technology of Polymers, National Council of Research, Via Campi Flegrei 34, Pozzuoli, 80078 Naples, Italy |
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Abstract: | We investigate the relation between the structure and the viscoelastic behavior of a model polymer nanocomposite system based
on a mixture of titanium dioxide (TiO2) nanoparticles and polypropylene. Above a critical volume fraction, Φ
c, the elasticity of the hybrids dramatically increases, and the frequency dependence of the elastic and viscous moduli reflects
the superposition of the independent responses of the suspending polymer melt and of an elastic particle network. In addition,
the elasticity of the hybrids shows critical behavior around Φ
c. We interpret these observations by hypothesizing the formation of a transient network, which forms due to crowding of particle
clusters. Consistent with this interpretation, we find a long-time, Φ-dependent, structural relaxation, which emphasizes the transient character of the structure formed by the particle clusters.
For times below this characteristic relaxation time, the elasticity of the network is Φ-independent and reminiscent of glassy behavior, with the elastic modulus, G′, scaling with frequency, ω, as G′∼ω
0.3. We expect that our analysis will be useful for understanding the behavior of other complex fluids where the elasticity of
the components could be superimposed. |
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Keywords: | Linear viscoelasticity Polymer nanohybrid Filler network |
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