Thierry Tassaing

Solubility in CO2 and carbonation studies of epoxidized fatty acid diesters: towards novel precursors for polyurethane synthesis

Novel linear polyurethanes were synthesized by bulk polyaddition of diamines with two vegetable-based biscarbonates produced from oleic acid methyl ester. Internal carbonated fatty acid diester (ICFAD) and terminal carbonated fatty acid diester (TCFAD) were obtained by the reaction of their epoxide precursors with CO2. Terminal epoxy fatty acid diester (TEFAD) was found to be more soluble and more reactive in CO2 than internal epoxy fatty acid diester (IEFAD). Polyurethanes obtained by polyaddition of TCFAD and ICFAD with diamines exhibit molecular weights up to 13 500 g mol−1 and glass transitions around −15 °C. Amide linkages were not observed when secondary diamine was used as the comonomer.

Drug loading of polymer implants by supercritical CO2 assisted impregnation: A review

Drug loaded implants also called drug-eluting implants have proven their benefits over simple implants. Among the developed manufacturing processes, the supercritical CO2 (scCO2) assisted impregnation has attracted growing attention to load Active Pharmaceutical Ingredients into polymer implants since it enables to recover a final implant free of any solvent residue and to operate under mild temperature which is suitable for processing with thermosensitive drugs. This paper is a review of the state-of-the-art and the application of the scCO2 assisted impregnation process to prepare drug-eluting implants. It introduces the process and presents its advantages for biomedical applications. The influences of the characteristics of the implied binary systems and of the experimental conditions on the drug loading are described. Then, the various current applications of this process for manufacturing drug-eluting implants are reviewed. Finally, the new emerging variations of this process are described.

Novel green fatty acid-based bis-cyclic carbonates for the synthesis of isocyanate-free poly(hydroxyurethane amide)s

Fatty acid-based bis-cyclic 5-membered carbonates containing amide linkages were prepared from methyl 10-undecenoate. The reaction in bulk of these bio-based carbonates with a series of di-amines led to poly(hydroxyurethane amide)s with molar masses up to 31 000 g mol−1. As expected, the so-formed bio-based thermoplastic poly(hydroxyurethane)s exhibit amorphous to semi-crystalline features with respect to the chemical structure of the monomers used.

Infrared spectroscopic study of hydrogen-bonding in water at high temperature and pressure

Abstract It is the purpose of this paper to present an infrared absorption spectroscopic study of the state of aggregation of water over a wide range of temperature (25–380°C) and pressure (1–250 bar) along the liquid-gas coexistence curve, and in the supercritical domain. The evolution of the spectral profiles asociated with the internal vibrational modes and with the librational motion has been investigated. In supercritical water, at T=380°C, low pressures (densities) in the range 25–50 bar (0.01–0.05 g.cm−3), only monomeric water is detected. Progressive increase of the pressure (density), from 50 to 250 bar (from 0.05 to 0.4 g.cm−3), shows clearly the appearance of water dimers and trimers. Finally, upon decreasing the temperature (250-25 °C) along the liquid-gas coexistence curve, one observes a continuous evolution of the shape of the infrared spectrum characteristic of the presence of oligomers of increasing size and for temperatures lower than 200°C, the progressive appearance of the hydrogen bond network.

Fluorinated Alcohols as Activators for the Solvent‐Free Chemical Fixation of Carbon Dioxide into Epoxides

The addition of fluorinated alcohols to onium salts provides highly efficient organocatalysts for the chemical fixation of CO2 into epoxides under mild experimental conditions. The combination of online kinetic studies, NMR titrations and DFT calculations allows understanding this synergistic effect that provides an active organocatalyst for CO2 /epoxides coupling.

Theoretical study on the chemical fixation of carbon dioxide with propylene oxide catalyzed by ammonium and guanidinium salts

The cycloaddition of carbon dioxide onto propylene oxide catalysed by ammonium and guanidinium salts has been investigated using density functional theory (DFT) in order to understand the catalytic mechanism and the role of the cation and the anion. Two different possible pathways were considered, but it has been found that the one whereby the activation of the epoxide by the onium salt occurs before the addition of CO2 was consistent with the experimental findings. The rate-determining step was found to be the ring opening of the epoxide that results from the nucleophilic attack of the anion of the catalyst on the non-substituted carbon of the epoxide ring. Moreover, we found that in order to have an efficient catalyst, it is necessary to have an anion with an ambivalent nature (a high nucleophilicity and good leaving group ability). Finally, it turns out that for a given anion, the guanidinium salt is more efficient than the ammonium salt in opening the epoxide ring, thanks to the ability of the guanidinium cation to form hydrogen bonds with the oxygen of the epoxide.

Calculation of IR frequencies and intensities in electrical and mechanical anharmonicity approximations: Application to small water clusters

We present a method for automatic computation of infrared (IR) intensities using parallel variational multiple window configuration interaction wave functions (P_VMWCI(2) algorithm). Inclusion of both mechanical and electrical anharmonic effects permits fundamental vibrational frequencies, including combinations and overtones, to be assigned. We use these developments to interpret the near-IR (NIR) and mid-IR (MIR) spectra of individual water clusters (H2O)(n) (n=1-4). Cyclic and linear systems are studied to provide equivalent reference theoretical data to investigate the structure of water as a function of density using NIR and MIR experimental spectra. Various density functional theory methods for generating the potential energy surface have been compared to reference results obtained at the CCSD(T) level [X. Huang et al., J. Chem. Phys. 128, 034312 (2008)]. For cyclic clusters, the IR intensities and frequencies obtained using B1LYP/cc-pVTZ are found to be in very good agreement with the available experimental values and of the same orders of magnitude as the reference theoretical values. These data are completed by the vibrational study of linear systems.

Organocatalytic promoted coupling of carbon dioxide with epoxides: a rational investigation of the cocatalytic activity of various hydrogen bond donors

A catalytic platform based on an onium salt used in combination with organic cocatalysts of various structures was developed for the efficient CO2/epoxide coupling under mild conditions. Through detailed kinetic studies by in situ FT-IR spectroscopy, a rational investigation of the efficiency of a series of commercially available hydrogen bond donors co-catalysts was realized and the influence of different parameters such as the pressure, the temperature, the catalyst loading, and the nature of the epoxide on the reaction kinetics was evaluated. Fluorinated alcohols were found to be more efficient than other hydrogen bond donor activators proposed previously in the literature under similar conditions.

Enhancement of Poly(vinyl ester) Solubility in Supercritical CO2 by Partial Fluorination: The Key Role of Polymer–Polymer Interactions

An enhancement of poly(vinyl ester) solubility in supercritical carbon dioxide (sc-CO(2)) can be achieved by decreasing the strength of the polymer-polymer interactions. To demonstrate this, a library of statistical copolymers of vinyl acetate and vinyl trifluoroacetate was synthesized by RAFT/MADIX polymerization with varying compositions at a given number-average molecular weight. These copolymers exhibited unprecedentedly low cloud-point pressures in sc-CO(2) at 40 °C compared with previously reported poly(vinyl esters). Surface tension measurements combined with a computational approach evidenced the prominent role played by polymer-polymer interactions.

Vibrational spectroscopic studies on the state of aggregation of water in carbon tetrachloride, in dioxane and in the mixed solvents

Abstract A detailed infrared study of the vibrational modes of water in dioxane, carbon tetrachloride and a mixed solvent as a function of concentration is reported. H 2 O/D 2 O mixtures have been used in order to isolate the uncoupled v(OH) and v(OD) modes. The data have been interpreted in terms of the state of aggregation of water molecules in a hydrophobic solvent and in a solvent to which hydrogen bonding can occur. It is shown that at very low concentrations ( x H 2 O = 5×10 −4 ) water exists in the monomeric form and can rotate rather freely. However, water is strongly self aggregated in a hydrophobic organic solvent for concentrations greater than x H 2 O = 5×10 −3 (ie if there are more than 5 water molecules in a 1000 solvent molecule ‘bath’). Evidence of distinct (dioxane) m (water) n complexes is found in dioxane solution and in the mixed solvent. However, as the water concentration is increased it is clear that a water/solvent ‘network’ is formed. The aggregation processes involving water depend critically, however, on the hydrophobicity of the solvent mixture.