H. S. Jeon

Structure‐property relationships in exfoliated polyisoprene (PI)/clay nanocomposites have been studied as a function of the clay concentration with rheometry, X‐ray diffraction, small‐angle X‐ray scattering, and transmission electron microscopy. The results presented here indicate that the interlayer spacing of layered silicates increases from 2 to at least approximately 14 nm because of the penetration of polymer molecules into the spacing between the silicate layers. The average aspect ratio (width/thickness) of the dispersed nanoplates is also estimated to be at least approximately 80. Additionally, the storage modulus of the nanocomposite exhibits frequency‐independent pseudo‐solidlike behavior above the percolation threshold [volume fraction of clay at the percolation threshold (ϕ_p) = 0.02] and shows large enhancements (up to approximately six orders of magnitude) in comparison with the storage modulus of PI when the volume fraction of clay (ϕ) is greater than ϕ_p. For the shear‐aligned PI/clay nanocomposites, an increase in the storage modulus with shear alignment is observed at ϕ < ϕ_p, whereas a decrease in the storage modulus is observed for ϕ > ϕ_p. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1000–1009, 2004