Inspired by the proclivity of various palladium sources to form nanoparticles in imidazoliumbased ionic liquids, we now report that tris-imidazolium salts bearing hexadecyl chains and a bridging mesitylene moiety are potent stabilizers of palladium nanoparticles efficiently prepared via a Chaudrettype hydrogenation of the bis(dibenzylideneacet- (0). The palladium nanoparticles have been isolated in pure form and characterized by 1 H nuclear magnetic resonance, transmission electron microscopy, electron diffraction and dynamic light scattering. The new materials proved effective in Suzuki cross-coupling at a loading of 0.2% palladi-um. Thus, using a tris-imidazolium iodide-palladium material, a series of biaryl products has been prepared starting from aryl bromides and some activated chlorides. The possibility that this catalytic activity might be due to the formation of palladium N-heterocyclic carbenes has been addressed through solid state 13 C NMR and the synthesis of an imidazolium analogue in which the acidic 2-H was replaced with a methyl group.

Palladium nanoparticles stabilized with tris-imidazolium tetrafluoroborates catalyze the stereoselective hydrosilylation of internal alkynes in a dry inert atmosphere to give (E)-vinylsilanes in excellent yields. In the presence of controlled amounts of water a transfer hydrogenation reaction takes place with the formation of (Z)-alkenes or the corresponding alkanes.

Ultrasound technology was proved as an efficient processing technique to obtain micro-molded specimens of polylactide (PLA) and polybutylene succinate (PBS), which were selected as examples of biodegradable polyesters widely employed in commodity and specialty applications. Operational parameters such as amplitude, molding force and processing time were successfully optimized to prepare samples with a decrease in the number average molecular weight lower than 6%. Ultrasonic waves also seemed an ideal energy source to provide effective disaggregation of clay silicate layers, and therefore exfoliated nanocomposites. X-ray diffraction patterns of nanocomposites prepared by direct micro-molding of PLA or PBS powder mixtures with natural montmorillonite or different organo-modified clays showed the disappearance of the 001 silicate reflection for specimens having up to 6 wt.% clay content. All electron micrographs revealed relatively homogeneous dispersion and sheet nanostructures oriented in the direction of the melt flow. Incorporation of clay particles during processing had practically no influence on PLA characteristics but enhanced PBS degradation when an organo-modifier was employed. This was in agreement with thermal stability data deduced from thermogravimetric analysis. Cold crystallization experiments directly performed on micro-molded PLA specimens pointed to a complex influence of clay particles reflected by the increase or decrease of the overall non-isothermal crystallization rate when compared to the neat polymer. In all cases, the addition of clay led to a clear decrease in the Avrami exponent.

Hybrid scaffolds constituted by a mixture of conducting and biodegradable polymers have been obtained by the electrospinning technique. Specifically, poly(3-thiophene metyl acetate) (P3TMA) and a copolymer derived from L-leucine which bears ester, urea and amide groups (PEU-co-PEA) have been employed. Both polymers have been selected because of their intrinsic properties and their high solubility in organic solvents. The biodegradable polymer renders continuous and homogeneous microfibers in most of the electrospinning conditions tested, appearing as an ideal carrier for the polythiophene derivative.A spontaneous phase separation has been observed for concentrated solutions of PEU-co-PEA and P3TMA in chloroform:methanol mixtures. The dense phase results enriched on the conducting polymer and can be successfully electrospun giving rise to scaffolds with up to 90 wt-% of P3TMA. Morphologic observations have indicated that continuous and regular microfibers are attained despite the high conducting polymer content. P3TMA presents a high doping level and leads to stable electrospun scaffolds by the simple addition of a low percentage of a high molecular weight carrier. The resulting scaffolds are practically amorphous and thermally stable, presenting also a pronounced electrochemical response and being electrochemically active. Thus, the formation of polarons and bipolarons at specific positions, the ability to exchange charge reversibly and the electrical stability of hybrid PEUco-PEA/P3TMA electrospun scaffolds and P3TMA alone are practically the same.