Structure and Dynamics of Polymer-Layered Silicate Nanocomposites

Abstract

The static and dynamic properties of polymer-layered silicate nanocomposites are discussed in the context of polymers in confined media. Despite the topological constraints imposed by the host lattice, mass transport of the polymer into the silicate layers (at least in the case of essentially non-polar polystyrene) appears to be unhindered and exhibits mobility similar to that of the pure polymer. However, both the local and global dynamics of the polymer in the hybrids are dramatically different from those in the bulk. On a local scale, intercalated polymer chains exhibit higher flexibility along their backbone along with a marked suppression (or even absence) of cooperative dynamics typically associated with the glass transition. On a global scale, relaxation of polymer chains either tethered to or in close proximity (<1 nm as in intercalated hybrids) to the host surface are dramatically altered and parallel those of other intrinsically anisotropic materials such as block copolymers and liquid crystals.

Review and critical analysis of the morphology of random ionomers across many length scales

“…Because the techniques that are used to deduce the existence of this phase depend on the hundreds of nanometer length scale, a critical discussion of this phase will be delayed until that time. However, it is appropriate to note that a rigid amorphous phase is not unique to ionomers; such a phase has been shown to occur in crystalline polymers [61] and nanocomposites [62,63].…”

Molecular probe technique for determining local thermal transitions: The glass transition at Silica/PMMA nanocomposite interfaces

“…Krishnamoorti et al [27] found complete suppression of cooperative dynamics associated with glass transition in polystyrene and polyethylene oxide intercalated nanocomposites with fluorohectorite. Ash et al [28] have shown that interactions between alumina nanoparticles and PMMA led to a depression in T g that was dependent on the size and concentration of the nanofiller used.…”

Rheology of Polymers with Nanofillers

“…One of the advantages of the linear region is the validity of the time-temperature (t-T) superposition principle-thus the possibility of extending the studies over many decades of frequency [Ferry, 1980]. Krishnamoorti et al [1996] reported the t-T superposition for the end-tethered CPNCs of PA-6 and poly(ε-caprolactone). The authors observed that orientation of clay platelets depends on the amplitude of dynamic stress.…”