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Poly(ε-caprolactone)/clay nanocomposites were prepared by in-situ ring-opening polymerization of ε-caprolactone by using dibutyltin dimethoxide as an initiator/catalyst. A nonmodified Na+−montmorillonite and two montmorillonites surface-modified by dimethyl 2-ethylhexyl (hydrogenated tallow alkyl) and methyl bis(2-hydroxyethyl) (hydrogenated tallow alkyl) ammonium cations, respectively, were used. The evolution of molecular weights was followed in relation to silicate surface modification and clay concentration. The alcohol-bearing organo-modified clay was a co-initiator for the polymerization reaction and thus controlled the molecular weight of the PCL chains. Furthermore, the number-average molecular weight of the growing PCL chains linearly increased with the monomer conversion. Nanocomposites were analyzed by small-angle X-ray diffraction, transmission electron microscopy, and thermogravimetry. The clay dispersion depended on the structure of the alkylammonium used to make the clay more hydrophobic. Exfoliated nanocomposites were formed when hydroxyl-containing alkylammonium was used; otherwise, intercalated structures were reported. Thermogravimetric analyses showed a higher degradation temperature for the exfoliated structures than for the intercalated ones, both of them exceeding the degradation temperature of unfilled poly(ε-caprolactone).

Poly(ε-caprolactone) (PCL) and poly(vinyl chloride) (PVC) layered silicate nanocomposites were prepared by combination of intercalative polymerization and melt intercalation. In a first step, high clay content PCL nanocomposites were prepared by in situ polymerization of -caprolactone intercalated between selected organo-modified silicate layers. The polymerization was catalyzed with dibutyltin dimethoxide in the presence of montmorillonites, the surface of which were previously exchanged with (functionalized) long alkyl chains ammonium cations. Then, these highly filled PCL nanocomposites were added as masterbatches in commercial PCL and PVC by melt blending. The intercalation of PCL chains within the silicate layers by in situ polymerization proved to be very efficient, leading to the formation of intercalated and/or exfoliated structures depending on the organo-clay. These masterbatches were readily dispersed into the molten PCL and PVC matrices yielding intercalated/exfoliated layered silicate nanocomposites which could not be obtained by melt blending the matrix directly with the same organo-modified clays. The formation of nanocomposites was assessed both by X-ray diffraction and transmission electronic microscopy. Interestingly, this so-called 'masterbatch' two-step process allowed for preparing PCL nanocomposites even with non-modified natural clay, i.e. sodium montmorillonite, which showed a material stiffness much higher than the corresponding microcomposites recovered by direct melt intercalation. The thermal stability of PCL nanocomposites as a function of clay content was investigated by thermogravimetry (TGA).

Among the various issues pertaining to the use of composite polymeric materials based on nanoparticles, the dispersion of the nanofillers in the matrix and the nature of the fillerpolymer interface are central. In many cases, poor dispersion results in agglomeration or phase separation, leading to a dramatic loss of the materials properties. To overcome this problem, a number of strategies have been developed with various degrees of success. They usually come at a high price, due to the necessity of modifying the surface state of the filler. Here, we report on novel carbon nanotubes-reinforced poly(dimethyl)siloxane nanocomposites and surprisingly, for which the use of "self pure" multiwall carbon nanotubes, i.e., without any surface functionalization or specific surface treatment, turns out to be the most efficient approach to impart new key-properties to the silicone matrix. Viscometric, rheological and theoretical studies have been performed that demonstrate the remarkable potential of dispersing a very tiny amount of "self pure" carbon nanotubes in silicone, paving the way to unexpected applications, e.g., in the field of fire endurance. Very interestingly, only tiny amounts of MWCNTs are required: usually less than 0.5 wt %. Those properties all rely on the nature of the nanotube-silicone interface interactions, which are dominated by additive CH-p interactions between the methyl groups of the polymer and the nanotube surface.Polydimethylsiloxane (PDMS) is the most common silicone elastomer owing to its ease of fabrication and advantageous chemical/physical properties, such as low surface energy, low glass transition temperature and high chain mobility.[1] Currently, to compensate for their poor mechanical properties, silicone materials have to be reinforced by incorporation of particulate materials, silica being the most commonly used filler. To date, the in situ filling process, where silica is generated into the elastomeric matrix, is the most efficient way to fill PDMS materials.[2] However, this reinforcement still requires a relatively high mass fraction of minerals (> 10 wt %).Over the past few years, much attention has been paid to polymer nanocomposites, which represent a rational alternative to conventional filled polymers, especially polymerlayered silicate nanocomposites. [3,4] In spite of their many potential applications, only a few reports have been published on polydimethylsiloxane nanocomposites. [5][6][7][8] The key-point for the improvement of properties as diverse as the mechanical, the thermal, and the barrier performances is the effective/ individual dispersion of the nanofillers in the matrix. To reach this objective, the type of nanofillers, their size and the nature of the interface formed within the matrix all have to be optimized. In this context, carbon nanotubes (CNTs) are of prime interest; however, they have a strong tendency to agglomerate in densely packed bundles, and their dispersion in polymers still remains a major challenge.Here we discuss first the spectacular change in...

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