Solvent-mediated pathways to gelation and phase separation in suspensions of grafted nanoparticles
Kumar, Sanat K.
KAUST Grant NumberKUS-C1-018-02
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AbstractWe explore the role of the solvent medium on the interplay between gelation and phase separation in suspensions of organosilicate planar hybrids grafted with hydrocarbon chains. We establish their phase diagram by means of dynamic light scattering, rheology and visual observations, and different routes to gelation, depending on the solvent used. In agreement with earlier works, the solvent quality for the grafted chains at a given temperature controls the balance between attractions and repulsions, and hence the phase diagram of the nanoparticles and their tendency to gel. Here we show how to tune the suspension state and hence its rheology. For decane, a good solvent for the hydrocarbon chains, gelation occurs at rather low volume fractions in the presence of phase separation. This is due to the interdigitation of solvent molecules with the grafted chains, resulting in their crystalline packing that promotes the attraction between particles. For toluene, a solvent of reduced quality for the hydrocarbon chains, no interdigitation takes place, and hence gelation is triggered by clustering at higher volume fractions before phase separation. Our results support the generic picture of complex kinetic arrest/phase separation interplay in soft matter, where phase separation can proceed, be interrupted or be completely inhibited. A number of interesting possibilities for tailoring the rheology of grafted colloidal systems emerge. © 2009 The Royal Society of Chemistry.
CitationAnyfantakis M, Bourlinos A, Vlassopoulos D, Fytas G, Giannelis E, et al. (2009) Solvent-mediated pathways to gelation and phase separation in suspensions of grafted nanoparticles. Soft Matter 5: 4256. Available: http://dx.doi.org/10.1039/b911244h.
SponsorsWe would like to thank B. Mueller and E. Pavlopoulou for the refractive index contrast and the SAXS measurements, respectively, as well as A. Larsen and D. Kendristaki for assistance in some PCS and rheology measurements. We are grateful to B. Loppinet for helpful discussions and to J. K. G. Dhont for insightful comments and for bringing to our attention refs. 38 and 73. This work was supported in part by the EU NoE-Softcomp (NMP3-CT-2004-502235). EPG acknowledges the support of Award No. KUS-C1-018-02, made by King Abdullah University of Science and Technology (KAUST).
PublisherRoyal Society of Chemistry (RSC)