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)

Structure and properties of a semifluorinated diblock copolymer modified epoxy blend

in Macromolecules (2007), 40(11), 4068-4074

Novel nanostructured thermosetting materials have been prepared by modification of an epoxy resin with a semifluorinated diblock copolymer, poly(heptadecafluorodecyl acrylate)-b-poly(caprolactone), PaF-b ... [more ▼]

Novel nanostructured thermosetting materials have been prepared by modification of an epoxy resin with a semifluorinated diblock copolymer, poly(heptadecafluorodecyl acrylate)-b-poly(caprolactone), PaF-b-PCL. In a first step, the phase behavior and linear viscoelasticity of PaF-b-PCL were investigated. According to the segregation regime, no order-order transitions were detected, being the order-disorder transition temperature beyond the degradation temperature. Atomic force microscopy (AFM) images of the block copolymer after different thermal treatments revealed that self-assembly takes place into spherical nanodomains, which is consistent with the copolymer composition. This block copolymer was further used to prepare a nanostructured thermoset blend with an epoxy resin. DSC and DMA analysis reveals microphase separation of PaF block from the epoxy-rich phase after curing. The PaF block self-assembled into wormlike and spherical micelles in the thermoset system. This nanostructured blend presented unique surface properties showing high hydrophobicity (upsilon = 109 degrees) and low surface energy (17 mN/m). [less ▲]

Controlled synthesis of carboxylic acid end-capped poly(heptadecafluorodecyl acrylate) and copolymers with 2-hydroxyethyl acrylate

in Journal of Polymer Science. Part A, Polymer Chemistry (2007), 45(8), 1499-1506

1H,1H,2H,2H-Heptadecafluorodecyl acrylate (AC8) was polymerized by reversible addition-fragmentation chain transfer and copolymerized with 2-hydroxyethyl acrylate with the formation of random and block ... [more ▼]

1H,1H,2H,2H-Heptadecafluorodecyl acrylate (AC8) was polymerized by reversible addition-fragmentation chain transfer and copolymerized with 2-hydroxyethyl acrylate with the formation of random and block copolymers, respectively. The kinetics of the (co)polymerization was monitored with H-1 NMR spectroscopy and showed that the homopolymerization and random copolymerization of AC8 were under control. As a result of this control and the use of S-1-dodecyl-S-(alpha,alpha'-dimethyl-alpha"-acetic acid)trithiocarbonate as a chain-transfer agent, the copolymer chains were end-capped by an a-carboxylic acid group. Moreover, the controlled polymerization of AC8 was confirmed by the successful synthesis of poly(1H,1H,2H,2H-heptadecafluorodecyl acrylate)-b-poly(2hydroxyethyl acrylate) diblock copolymers, which were typically amphiphilic compounds. [less ▲]

Motional heterogeneity of intercalated species in modified clays and poly(epsilon-caprolactone)/clay nanocomposites

in Langmuir (2006), 22(10), 4818-4824

Modified laponites and synthetic saponites are used as precursors for the preparation of poly(epsilon-caprolactone) (PCL)/clay nanocomposites. The structure and dynamics of species intercalated in the ... [more ▼]

Modified laponites and synthetic saponites are used as precursors for the preparation of poly(epsilon-caprolactone) (PCL)/clay nanocomposites. The structure and dynamics of species intercalated in the modified clays and the corresponding nanocomposites are characterized by X-ray diffraction and magic-angle spinning NMR. The influence of the headgroup, the hydrocarbon chain length, and the loading of the surfactant on the nanocomposite formation are discussed. The yield of PCL intercalation is related to the probability of direct polymer-clay interactions and to the size of the clay platelets. Relaxation times in the laboratory and rotating frames that allow characterization of fast and slow molecular dynamics in these systems are discussed, showing a motional heterogeneity of the intercalated species. [less ▲]

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

in Studies in Surface Science and Catalysis (2006), 160

X-ray microtomography coupled with image analysis: a useful tool or 3D characterization of polymer foams

Conference (2005, October)

Synthesis and foaming of polymer nanocomposites and microspheres in supercritical CO2

Poster (2005, June 01)