Supercritical carbon dioxide as an efficient process to obtain specialty organoclays : from lab preparation to pre-industrial production

Conference (2008, October 07)

Production of highly efficient nanoclays in supercritical carbon dioxide

Poster (2008, August 31)

Characterization of the porous structure of biodegradable scaffolds obtained with supercritical CO2 as foaming agent

in Journal of Porous Materials (2008), 15(4), 397-403

Poly(ε-caprolactone) foams were prepared, via a batch process, by using supercritical CO2 as foaming agent. Their porous structure was characterized through mercury porosimetry, helium and mercury ... [more ▼]

Poly(ε-caprolactone) foams were prepared, via a batch process, by using supercritical CO2 as foaming agent. Their porous structure was characterized through mercury porosimetry, helium and mercury pycnometry, scanning electron microscopy (SEM) and X-ray microtomography observations coupled with image analysis. The pore size distributions obtained by these two latter techniques show that the pore structure is more homogeneous when the foaming process is performed under a high CO2 saturation pressure (higher than 250 bars). [less ▲]

Supercritical carbon dioxide, a tool for the dispersion ROP of lactone and PCL foaming: Part A

Poster (2008, June 02)

Aliphatic polyesters, namely polylactide (PLA) and poly-ε-caprolactone (PCL) are biodegradable and biocompatible materials that find applications as resorbable suture (PLA) and drugs delivery vectors (PCL ... [more ▼]

Aliphatic polyesters, namely polylactide (PLA) and poly-ε-caprolactone (PCL) are biodegradable and biocompatible materials that find applications as resorbable suture (PLA) and drugs delivery vectors (PCL). Nevertheless, these polymers were mainly prepared by ring opening polymerization using aluminum alkoxide or tin alkoxide initiators in organic media. Recently, the use of supercritical carbon dioxide as polymerization medium was proposed as a potential alternative to the use toxic organic solvents. Nevertheless, due to the non-solubility of PCL in this medium, the growing chains rapidly precipitate during their synthesis leading to the formation of a bulky material that is typical of a precipitation polymerization. This work aims at investigating the dispersion ring-opening polymerization (ROP) of ε-caprolactone in the presence of fluoropolymer-based stabilizers, that were prepared by combining the ring opening polymerization of ε-caprolactone and atom transfer radical polymerization of heptadecafluorodecylacrylate (AC8) and so, stabilizing PCL micrometric particles in supercritical carbon dioxide. In practice, the ROP of CL was initiated by dibutyltin dimethoxide in the presence of PCL-b-PAC8 diblock stabilizers of differents molecular weight and composition. After 24h at 40°C, PCL was collected as a powder that consists of small-sized microspheres. Finally, post-polymerization purification of PCL (removal of tin catalyst that may lead to toxicological problems) was demonstrated to be quite feasible by supercritical fluid extraction (SFE) leading to the preparation of PCL with low catalytic residues. The second goal of this work aims at reporting on the use of sc CO2 for the preparation of foams of poly(epsilon-caprolactone) (PCL), that could be useful in the packaging sector and/or the biomedical sector as potential scaffolds for tissue engineering but also as substitutes for polystyrene thermoformed trays. The method that consists of saturating a polymer with a compressed or supercritical fluid, such as carbon dioxide followed by depressurization and polymer expansion was investigated. Indeed, no residual product is left in the foam, no toxic gas is produced and no resort to hydrocarbon solvents is required. Moreover, CO2 is cheap, non-toxic, recyclable, non-flammable and the technology of CO2-assisted foaming can be used in either a batch mode or in a continuous mode within a high-pressure extruder. [less ▲]

Supercritical carbon dioxide : a new method for the organomodification of natural clays

Conference (2008, May 05)

Extrusion foaming of poly(styrene-co-acrylonitrile) using supercritical carbon dioxide

Conference (2008, May 05)

Supported ATRP of fluorinated methacrylates in supercritical carbon dioxide : preparation of scCO2 soluble polymers with low catalytic residues

in Chemical Communications (2008), (44), 5803-5805

Synthesis of poly( 2,2,2-trifluoroethyl methacrylate) by supported ATRP was investigated in supercritical carbon dioxide using a copper salt ligated to a polymeric ligand immobilised onto silica; after ... [more ▼]

Synthesis of poly( 2,2,2-trifluoroethyl methacrylate) by supported ATRP was investigated in supercritical carbon dioxide using a copper salt ligated to a polymeric ligand immobilised onto silica; after polymerisation, fluorinated polymers with well defined molecular weight and low polydispersity were obtained. [less ▲]

Swelling behavior and release properties of pH-sensitive hydrogels based on methacrylic derivatives

in Acta Pharmaceutica (Zagreb, Croatia) (2007), 57(3), 301-314

The purpose of this study is to develop novel intestinal-specific drug delivery systems with pH sensitive swelling and drug release properties. Methacrylic-type polymeric prodrugs were synthesized by free ... [more ▼]

The purpose of this study is to develop novel intestinal-specific drug delivery systems with pH sensitive swelling and drug release properties. Methacrylic-type polymeric prodrugs were synthesized by free radical copolymerization of methacrylic acid, poly(ethyleneglycol monomethyl ether methacrylate) and a methacrylic derivative of N-(4-hydroxyphenyl)-2-(4-methoxyphenyl) acetamide in the presence of ethylene glycol dimethacrylate as crosslinking agent. The effect of copolymer composition on the swelling behavior and hydrolytic degradation were studied in simulated gastric (SGF, pH 1.2) and intestinal fluids (SIF, pH 7.0). The dynamic swelling behavior of these hydrogels was investigated to determine the mechanism of water transport through these hydrogels. The mechanism of water transport through the gels was significantly affected by the pH of the swelling medium and became more relaxation-controlled in a swelling medium of pH 7.0. The swelling and hydrolytic behaviors of hydrogels were dependent on the content of methacrylic acid (MAA) groups and caused a decrease and increase in gel swelling in SGF and SIF, respectively. Drug release studies showed that the increasing content of MAA acid in the copolymer enhances hydrolysis in SIF. These results suggest that pH-sensitive systems could be useful for preparation of a muccoadhesive system and controlled release of N-(4-hydroxyphenyl)-2-(4-methoxyphenyl) acetamide. [less ▲]

Production of highly efficient nanoclays in supercritical carbon dioxide

Poster (2007, August 31)

Preparation of specialty nanoclays in supercritical carbon dioxide

Conference (2007, August 29)