Elasticity, fracture and thermoreversible gelation of highly filled physical gels⋆
Department of Materials Science and Engineering, Northwestern University, 60208-3108, Evanston, IL, USA
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Accepted: 12 June 2005
Published online: 30 August 2005
We describe a physically associating triblock copolymer-based gel that exhibits a reversible transition between solid and liquid states at a temperature of approximately 55° C. The thermal transition of the gel enables us to compare the properties of liquid suspensions and elastic composites with identical particle loadings, with particle volume fractions as large as 0.55. The suspension viscosity and the composite elasticity scale in a similar manner with the overall particle volume fraction, a result that is rationalized in terms of an effective strain amplification factor that depends only on the particle loading. Measured values of the strain amplification factor are in good agreement with the expected form for well-dispersed spheres. We also find that the elastic composites are exceptionally strong, with fracture strengths that exceed the modulus of the base gel by a factor of 100 or more. Deviations from purely elastic behavior became important for high particle volume fractions, and were probed by stress relaxation experiments.
PACS: 83.80.Hj Suspensions, dispersions, pastes, slurries, colloids – / 83.80.Kn Physical gels and microgels – / 83.80.Wx Filled elastomers –
© EDP Sciences, Società Italiana di Fisica and Springer-Verlag, 2005