The recent surge of interest in nanoscale materials has been inspired, in part, by the realization that nanoscale materials often exhibit physical and chemical properties that are dramatically different from their bulk counterparts.1-3 A promising strategy for synthesizing nanophase organic-inorganic hybrids is intercalation of polymers in layered hosts.4-18 In most cases, the synthesis involves either intercalation of a suitable monomer and subsequent polymerization4-16 or polymer intercalation from solution.16-18 For most technologically important polymers, both approaches are limited since neither a suitable monomer nor a compatible polymer-host solvent system is always available. We report a more versatile synthetic approach based on direct polymer melt intercalation. Using an organically modified layered silicate, different polymers of varying degrees of polarity and crystallinity have been intercalated, including for the first time polystyrene.During polymer intercalation from solution, a relatively large number of solvent molecules need to be desorbed from the host to accommodate the incoming polymer chains. The desorbed solvent molecules gain one translational degree of freedom and the resulting entropic gain compensates for the decrease in conformational entropy (1)

The Stardust spacecraft collected thousands of particles from comet 81P/Wild 2 and returned them to Earth for laboratory study. The preliminary examination of these samples shows that the nonvolatile portion of the comet is an unequilibrated assortment of materials that have both presolar and solar system origin. The comet contains an abundance of silicate grains that are much larger than predictions of interstellar grain models, and many of these are high-temperature minerals that appear to have formed in the inner regions of the solar nebula. Their presence in a comet proves that the formation of the solar system included mixing on the grandest scales.

The bulk of the comet 81P/Wild 2 (hereafter Wild 2) samples returned to Earth by the Stardust spacecraft appear to be weakly constructed mixtures of nanometer-scale grains, with occasional much larger (over 1 micrometer) ferromagnesian silicates, Fe-Ni sulfides, Fe-Ni metal, and accessory phases. The very wide range of olivine and low-Ca pyroxene compositions in comet Wild 2 requires a wide range of formation conditions, probably reflecting very different formation locations in the protoplanetary disk. The restricted compositional ranges of Fe-Ni sulfides, the wide range for silicates, and the absence of hydrous phases indicate that comet Wild 2 experienced little or no aqueous alteration. Less abundant Wild 2 materials include a refractory particle, whose presence appears to require radial transport in the early protoplanetary disk.