Polymer/layered silicate nanocomposites: a review from preparation to processing

Ionic liquids are salts that are liquid at low temperature (<100 degrees C) which represent a new class of solvents with nonmolecular, ionic character. Even though the first representative has been known since 1914, ionic liquids have only been investigated as solvents for transition metal catalysis in the past ten years. Publications to date show that replacing an organic solvent by an ionic liquid can lead to remarkable improvements in well-known processes. Ionic liquids form biphasic systems with many organic product mixtures. This gives rise to the possibility of a multiphase reaction procedure with easy isolation and recovery of homogeneous catalysts. In addition, ionic liquids have practically no vapor pressure which facilitates product separation by distillation. There are also indications that switching from a normal organic solvent to an ionic liquid can lead to novel and unusual chemical reactivity. This opens up a wide field for future investigations into this new class of solvents in catalytic applications.

Ionic Liquids-New "Solutions" for Transition Metal Catalysis.

For economical and ecological reasons, synthetic chemists are confronted with the increasing obligation of optimizing their synthetic methods. Maximizing efficiency and minimizing costs in the production of molecules and macromolecules constitutes, therefore, one of the most exciting challenges of synthetic chemistry.1-3 The ideal synthesis should produce the desired product in 100% yield and selectivity, in a safe and environmentally acceptable process.4 It is now well recognized that organometallic homogeneous catalysis offers one of the most promising approaches for solving this basic problem.2 Indeed, many of these homogeneous processes occur in high yields and selectivities and under mild reaction conditions. Most importantly, the steric and electronic properties of these catalysts can be tuned by varying the metal center and/or the ligands, thus rendering tailor-made molecular and macromolecular structures accessible.5,6 Despite the fact that various efficient methods, based on organometallic homogeneous catalysis, have been developed over the last 30 years on the laboratory scale, the industrial use of homogeneous catalytic processes is relatively limited.7 The separation of the products from the reaction mixture, the recovery of the catalysts, and the need for organic solvents are the major disadvantages in the homogeneous catalytic process. For these reasons, many homogeneous processes are not used on an industrial scale despite their benefits. Among the various approaches to address these problems, liquidliquid biphasic catalysis (“biphasic catalysis”) has emerged as one of the most important alternatives.6-11 The concept of this system implies that the molecular catalyst is soluble in only one phase whereas the substrates/products remain in the other phase. The reaction can take place in one (or both) of the phases or at the interface. In most cases, the catalyst phase can be reused and the products/substrates are simply removed from the reaction mixture by decantation. Moreover, in these biphasic systems it is possible to extract the primary products during the reaction and thus modulate the product selectivity.12 For a detailed discussion about this and other concepts of homogeneous catalyst immobilization, the reader is referred elsewhere.6,7 These biphasic systems might combine the advantages of both homogeneous (greater catalyst efficiency and mild reaction conditions) and heterogeneous (ease of catalyst recycling and separation of the products) catalysis. The advent of water-soluble organometallic complexes, especially those based on sulfonated phosphorus-containing ligands, has enabled various biphasic catalytic reactions to be conducted on an industrial scale.13-15 However, the use of water as a * Corresponding author. Fax: ++ 55 51 3316 73 04. E-mail: dupont@iq.ufrgs.br. 3667 Chem. Rev. 2002, 102, 3667−3692

https://www.chem.ccu.edu.tw/~joyce/referance/gump/IL/Chem.%20Rev.%202002,%20102,%203667.pdf

Ionic liquid (molten salt) phase organometallic catalysis.

Catalytic reactions in ionic liquids

A review on polymer–layered silicate nanocomposites

Nano-biocomposites: Biodegradable polyester/nanoclay systems

Starch-based nano-biocomposites

Vapor barrier properties of polycaprolactone montmorillonite nanocomposites: effect of clay dispersion

The last decade has seen the development of an alternative chemistry, which intends to reduce the human impact on the environment. The polymers are obviously involved into this tendency and numerous bio-sourced plastics (bioplastics), such as polylactide, plasticized starch, etc., have been elaborated. However, even if a lot of commercial products are now available, their properties (mechanical properties, moisture sensitivity) have to be enhanced to be really competitive with the petroleum-based plastics. One of the most promising answers to overcome these weaknesses is the elaboration of nano-biocomposites, namely the dispersion of nano-sized filler into a biopolymer matrix. This review reports the last developments in nano-biocomposites based on polysaccharides and nanoclays. The main elaboration strategies developed in starch, chitosan, cellulose acetate and pectin based nano-biocomposites elaborated with montmorillonite as the nanofiller are exposed herein. The corresponding dispersion state and properties are discussed.

Progress in nano-biocomposites based on polysaccharides and nanoclays

Mixed culture polyhydroxyalkanoate (PHA) production from volatile fatty acid (VFA)-rich streams: Effect of substrate composition and feeding regime on PHA productivity, composition and properties

Eric Pollet

Papers

Nano-biocomposites: Biodegradable polyester/nanoclay systems

Starch-based nano-biocomposites

Vapor barrier properties of polycaprolactone montmorillonite nanocomposites: effect of clay dispersion

Progress in nano-biocomposites based on polysaccharides and nanoclays

Mixed culture polyhydroxyalkanoate (PHA) production from volatile fatty acid (VFA)-rich streams: Effect of substrate composition and feeding regime on PHA productivity, composition and properties