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See detailα-chloro-ε-caprolactone, a versatile precursor for grafting of aliphatic polyesters
Riva, Raphaël ULg; Lenoir, Sandrine ULg; Lecomte, Philippe ULg et al

Poster (2009, September 17)

Macromolecular engineering is one of the most powerful tool to synthesise many polymers of various architectures and with tailored properties. This contribution aims at reporting on a novel strategy for ... [more ▼]

Macromolecular engineering is one of the most powerful tool to synthesise many polymers of various architectures and with tailored properties. This contribution aims at reporting on a novel strategy for the macromolecular engineering of poly-ε-caprolactone (PCL) which is based on the use of a dual monomer / initiator compound, α-chloro-ε-caprolactone (αClεCL). Indeed, αClεCL is not only polymerizable by ring opening initiated by metal alkoxides, but it is also an initiator for the atom transfer radical polymerization (ATRP) of vinyl monomers, so leading easily to the synthesis of macromonomers. Polystyrene macromonomer has been prepared by this method and successfully copolymerized with ε-caprolactone (εCL) with formation of the corresponding grafted PCL. αClεCL is also a precursor of copolyesters with εCL that bear pendant chlorides. These (co)polyesters have been used as macroinitiators for the ATRP of methyl methacrylate in order to synthesise the corresponding graft copolymer. On the other hand, the pendant chlorides of poly(αClεCL-co-εCL) copolyesters were easily converted into azide with formation of the corresponding azide bearing copolyester. This copolyester was then reacted with an alkyne bearing an ATRP initiator by “Click chemistry”. The conversion of chlorides into more efficient ATRP initiators led to the improvement of the initiation efficiency of the macroinitiator. [less ▲]

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See detailNew developments in the functionalization of aliphatic polyesters by "click" copper-catalyzed azide-alkyne cycloaddition
Lecomte, Philippe ULg; Riva, Raphaël ULg; Schmeits, Stephanie ULg et al

Conference (2009, June 03)

Nowadays, biodegradable and biocompatible aliphatic polyesters are widely used as environmentally friendly thermoplastics and biomaterials. Nevertheless, the absence of any pendant functional group is a ... [more ▼]

Nowadays, biodegradable and biocompatible aliphatic polyesters are widely used as environmentally friendly thermoplastics and biomaterials. Nevertheless, the absence of any pendant functional group is a severe limitation for the development of novel applications. Our strategy aiming at functionalizing aliphatic polyesters relies on the “click” copper-catalyzed cycloaddition (CuAAC) of alkynes duly substituted by functional groups or even chains onto PCL bearing pendant azides. The aliphatic polyesters bearing pendant azides have been very efficiently synthesized by a straightforward approach, which relies on the ring-opening copolymerization of αClεCL (or γBrεCL) and εCL (or lactide) followed by reaction with sodium azide to convert pendant chlorides or bromides into azides. The alternative reported by Emrick et al. is based on the CuAAC reaction of azides substituted by any functional group onto copolyesters of poly(ε-caprolactone) bearing pendant alkynes. Interestingly enough, Emrick et al. carried out the CuAAc reaction in water at 80°C. Unfortunately, it turned out, at least in our hands, that these conditions can not be extended to the derivatization of more sensitive aliphatic polyesters because degradation was then unavoidable. Nevertheless, we found out that degradation can be minimized whenever the CuAAC reaction is carried out in an organic solvent at lower temperature. Typically, the CuAAC reaction was carried out in DMF or THF at 35°C. Recently, it was shown that supercritical carbon dioxide can be used as a more environmentally friendly solvent than DMF or THF. The contamination by catalytic residues of aliphatic polyesters functionalized by the CuAAC reaction is a severe limitation in view of future applications, especially in the biomedical field. In the last part of this talk, a special attention will be paid on our current efforts to get rid of copper residues. [less ▲]

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See detailFunctionalization of aliphatic polyesters by “click chemistry” in supercritical carbon dioxide
Grignard, Bruno ULg; Schmeits, Stephanie ULg; Riva, Raphaël ULg et al

Poster (2009, May 14)

The combination of ring-opening polymerization of lactones and “click” copper-catalyzed Huisgen’s [3+2] cycloaddition is known to be a very efficient strategy for the functionalization of poly(ε ... [more ▼]

The combination of ring-opening polymerization of lactones and “click” copper-catalyzed Huisgen’s [3+2] cycloaddition is known to be a very efficient strategy for the functionalization of poly(ε-caprolactone) (PCL) and poly(lactic acid) (PLA). Whenever the “click” reaction occurs in an organic solvent (THF or DMF), at relatively low temperature (35°C) and within short reaction time (2 hours), no significant degradation of polyester chains is detected. This strategy was implemented in previous works to graft alkynes substituted by different functional groups, such as hydroxyl, tertiary amines, acrylates or ammonium salts onto azide-functionalized PCL. Moreover, this approach was previously extended to the synthesis of grafted copolymers, either by the grafting of omega-alkyne-PEO onto azide-functionalized aliphatic PLA or PCL (“grafting onto” technique) either by grafting of an ATRP initiator followed by the polymerization of vinyl monomers, such as styrene (“grafting from” technique). These functionalized aliphatic polyesters are promising materials for the development of new biomedical devices. In this work, novel conditions were implemented for the “click” reaction in order to avoid the use of organic solvents and to limit the amount of catalyst remnants in functionalized aliphatic polyesters. Toward this end, if was found that the functionalization by “click” chemistry can be efficiently carried out in supercritical carbon dioxide rather than in THF or DMF. For that sake, it turned out necessary to synthesize a perfluorinated polyamine in order to solubilize the catalyst in supercritical carbon dioxide. Aliphatic polyesters are not soluble in supercritical carbon dioxide. Nevertheless, even under heterogeneous conditions, the functionalization of aliphatic polyesters by “click” chemistry is quantitative. Interestingly enough, no degradation was observed. Last but not least, the copper catalyst was easily removed by supercritical fluid extraction leading to a very low content of residual copper in the final copolyester. [less ▲]

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See detailDéveloppement d'un implant intra-péritonéal contre l'endométriose
Krier, Fabrice ULg; Evrard, Brigitte ULg; Piel, Géraldine ULg et al

Scientific conference (2009, February 03)

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See detailRecent advances in the synthesis of aliphatic polyesters by “click” chemistry
Riva, Raphaël ULg; Jérôme, Christine ULg; Jérôme, Robert ULg et al

Conference (2008, September 11)

Since the discovery of Sharpless and Meldal, the copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) is more and more popular in the field of macromolecular engineering owing to its robustness, its ... [more ▼]

Since the discovery of Sharpless and Meldal, the copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) is more and more popular in the field of macromolecular engineering owing to its robustness, its high tolerance to a wide range of functional groups without any need of protecting groups and the absence of side-products. This reaction is known to be a very efficient “click” reaction as defined by Sharpless. The chemical modification of aliphatic polyesters remains, at the time being, a very difficult task to achieve because of the very limited number of efficient chemical reactions, which can be implemented in the absence of chain degradation. The main purpose of this contribution is to report on the most recent advances on the use of CuAAC to derivatize aliphatic polyesters (Scheme 1). Interestingly enough, it was recently shown that CuAAC carried out onto aliphatic polyesters attached with either azides or alkynes is very efficient under mild conditions, which limit undesirable degradation. Several functional groups were grafted onto aliphatic polyesters by CuAAC without using any protection/deprotection reactions. The CuAAC is also very efficient to prepare aliphatic polyesters with various architectures as highlighted by the synthesis of graft copolymers, star-shaped copolymers and networks. This “click” chemistry has been combined with other polymerization mechanism such as ATRP in order to extend further the range of available polymers. [less ▲]

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See detailMacromolecular engineering of biodegradable polyesters by ring-opening polymerization and 'Click' chemistry
Lecomte, Philippe ULg; Riva, Raphaël ULg; Jérôme, Christine ULg et al

in Macromolecular Rapid Communications (2008), 29(12-13), 982-997

Biodegradability makes aliphatic polyesters valuable candidates for biomaterials and environmentally friendly thermoplastics. Nevertheless, their chemical modification, which is mandatory for a series of ... [more ▼]

Biodegradability makes aliphatic polyesters valuable candidates for biomaterials and environmentally friendly thermoplastics. Nevertheless, their chemical modification, which is mandatory for a series of potential applications, is usually a problem because it must be carried out under very mild conditions in order to prevent degradation by hydrolysis and/or transesterification from occurring. In this review, the copper(i) -catalyzed azide-alkyne cycloaddition, which is a click reaction, is shown to be very efficient to bypass these problems and to tailor the macromolecular architecture and functionality of those polyesters without facing undesired degradation reactions. [less ▲]

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See detailContribution of "click chemistry" to the synthesis of antimicrobial aliphatic copolyester
Riva, Raphaël ULg; Lussis, Perrine ULg; Lenoir, Sandrine ULg et al

in Polymer (2008), 49(8), 2023-2028

A straightforward strategy is proposed to impart antimicrobial properties to biodegradable poly(oxepan-2-one) (poly(epsilon-caprolactone) or PCL), which is based on the grafting of pendant ammonium salts ... [more ▼]

A straightforward strategy is proposed to impart antimicrobial properties to biodegradable poly(oxepan-2-one) (poly(epsilon-caprolactone) or PCL), which is based on the grafting of pendant ammonium salts by "click" chemistry. First, statistical copolymerization of 3-chlorooxepan-2-one (alpha-chloro-epsilon-caprolactone or alpha Cl epsilon CL) with oxepan-2-one (epsilon-caprolactone or epsilon CL) was initiated by 2,2-dibutyl-2-stanna-1,3-dioxepane (DSDOP). In a second step, pendant chlorides were converted into azides by reaction with sodium azide (NaN3). Finally, quaternary ammonium containing alkynes were quantitatively added to the pendant azide groups of PCL by the copper-catalyzed Huisgen's 1,3-dipolar cycloaddition, which is a typical "click" reaction. An alternative two-step strategy based on the cycloaddition of the amine containing alkyne onto the pendant azides, followed by quaternization turned out to be less efficient. The antimicrobial activity was analyzed by the "shaking flask method" in the presence of Escherichia coli [less ▲]

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See detailSynthesis of novel functional aliphatic polyesters by association of ring-opening polymerization and click chemistry
Lecomte, Philippe ULg; Schmeits, Stephanie ULg; Riva, Raphaël ULg et al

Conference (2008, April 09)

Nowadays, biodegradable and biocompatible aliphatic polyesters are widely used as environmentally friendly thermoplastics and biomaterials. Nevertheless, the absence of any functional group along the ... [more ▼]

Nowadays, biodegradable and biocompatible aliphatic polyesters are widely used as environmentally friendly thermoplastics and biomaterials. Nevertheless, the absence of any functional group along the chain is a severe limitation for the development of new applications. Very recently, it was reported by Emrick et al. and by us that copper(I)-mediated 1,3-dipolar Huisgen's cycloaddition of alkynes and azides, the most widely used “click” reaction in the frame of macromolecular engineering, is very efficient to derivatize aliphatic polyesters. Due to the tolerance for many functional groups, cumbersome protection and deprotection steps are not needed. One main advantage of copper(I)-mediated Huisgen's cycloaddition compared to other reactions previously used to derivatize aliphatic polyesters relies on the mildness of the experimental conditions, which results in limited degradation. Our most recent results dealing with the combination of “click” chemistry and ring-opening polymerization towards functional PCL and PLA, networks, graft and hyperbranched copolymers will be highlighted. [less ▲]

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See detailPH-responsive biodegradable amphiphilic networks
Zednik, Jiri; Riva, Raphaël ULg; Lussis, Perrine ULg et al

in Polymer (2008), 49(3), 697-702

Copper-mediated azide - alkyne Huisgen's 1,3-dipolar cycloaddition is a "click" reaction that was successfully used to prepare pH-responsive, amphiphilic and biodegradable networks. Indeed, this reaction ... [more ▼]

Copper-mediated azide - alkyne Huisgen's 1,3-dipolar cycloaddition is a "click" reaction that was successfully used to prepare pH-responsive, amphiphilic and biodegradable networks. Indeed, this reaction proved to be very efficient in the "one pot" grafting of amino alkyne onto azide containing poly(epsilon-caprolactone) and the cross-linking of these chains by alpha,omega-dialkynyl poly(ethylene oxide). The pH-controlled release of guests hosted during the cross-linking step was illustrated with an entrapped model dye. [less ▲]

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See detailSynthesis of eight-shaped and star-shaped poly(ε-caprolactone) and their amphiphilic derivatives
Li, Haiying; Riva, Raphaël ULg; Kricheldorf, Hans R. et al

in Chemistry : A European Journal (2008), 14(1), 358-368

Spirocyclic tin dialkoxides are unique initiators for the ring-expansion polymerization of lactones leading to complex, but well-defined macromolecular architectures. In a first example, -caprolactone (CL ... [more ▼]

Spirocyclic tin dialkoxides are unique initiators for the ring-expansion polymerization of lactones leading to complex, but well-defined macromolecular architectures. In a first example, -caprolactone (CL) was polymerized, followed by the resumption of polymerization of a mixture of CL and CL -substituted by a chloride (ClCL), so leading to living eight-shaped chains. Upon hydrolysis of the alkoxides, a four-arm star-shaped copolyester was formed, whose each arm was grafted by conversion of the chloride units into azides, followed by the Huisgen's [3+2] cycloaddition of alkyne end-capped poly(ethylene oxide) (PEO) onto the azide substituents. The complexity of this novel amphiphilic architecture was increased further by substituting the four-arm interconnecting PCL by an eight-shaped PCL. In a preliminary step, CL was polymerized followed by a few units of CL -substituted by an acrylate. The intramolecular photo-crosslinking of the acrylates adjacent to the tin dialkoxides was effective in stabilizing the eight-shaped polyester while preserving the chain growth sites. This quite unusual tetrafunctional macroinitiator was used to copolymerize CL and ClCL, followed by hydrolysis of the alkoxides, conversion of the chloride units into azides and grafting of the four arms by PEO (see above). This architecture reported for the very first time is nothing but a symmetrical four-tail eight-shaped copolyester macromolecule. [less ▲]

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See detailSynthesis of novel functional aliphatic polyesters
Schmeits, Stephanie ULg; Riva, Raphaël ULg; Jérôme, Christine ULg et al

in Polymer Preprints (2008), 49(1), 222-223

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See detailDEVELOPMENT OF AN INTRAPERITONEAL IMPLANT FOR THE ENDOMETRIOSIS TREATMENT
Krier, Fabrice ULg; Nizet, Dominique; Riva, Raphaël ULg et al

Poster (2008)

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See detailMacromolecular engineering of cyclic aliphatic polyesters by ring-opening polymerization and "click" chemistry
Lecomte, Philippe ULg; Li, Haiying; Riva, Raphaël ULg et al

Conference (2007, September 04)

The last decades have witnessed a steadily increasing progress in the macromolecular engineering of the main families of synthetic polymers. Ring-shaped copolymers show a unique topology due to the ... [more ▼]

The last decades have witnessed a steadily increasing progress in the macromolecular engineering of the main families of synthetic polymers. Ring-shaped copolymers show a unique topology due to the absence of any chain-end and exhibit distinct properties from their linear counterparts, such as glass transition temperature, order-disorder transition, reduced viscosity, lower hydrodynamic volumes. This communication aims at reporting on a novel route to biodegradable cyclic polyesters. Our strategy is based on the work of Prof. Kricheldorf who initiated the ring-opening polymerization of ε-caprolactone by cyclic tin dialkoxides, e.g., 2,2-dibutyl-2-stanna-1,3-dioxepane (DSDOP) in order to obtain “living” macrocyclic PCL, still containing two endocyclic tin-oxygen bonds. In this work, the resumption of polymerization by a few units of ε-caprolactone substituted by an acrylic unit, e.g., 1-(2-oxooxepan-3-yl)ethyl prop- 2-enoate, followed by intramolecular photo-crosslinking of pendant unsaturations and finally by hydrolysis gave rise to macrocyclic PCL. As a rule, this strategy is very well-suited for the synthesis of high molecular weight PCL. Moreover, tin alkoxides were kept untouched after the cross-linking step and remained thus available for further macromolecular engineering. The process was extended to the synthesis of other architectures such as sun-shaped, two-tail tadpoleshaped, and eight-shaped copolyesters. The second part of the lecture, it will be shown that the copper(I)-catalyzed Huisgen’s [3+2] cycloaddition, which is the most popular “Click" reaction, is very efficient to graft alkynes, duly substituted by functional groups or chains, onto aliphatic copolyesters bearing pendant azides. Interestingly enough, mild conditions were found and no degradation was observed during the “click” derivatization of copolyesters of PCL. The “click” reactions of alkynes onto pendant azides of copolyesters of PLA, by far more sensitive than PCL, was also successfully carried out without any detectable degradation. ”Click” chemistry is very versatile because this reaction was successfully implemented to graft functional groups or chains directly onto ω-azido-ε-caprolactone, without any ring-opening of the lactone, in order to make available a new range of functional caprolactones. Finally, the “click” grafting of PEO onto the tails of tadpole-shaped copolymers will be shown to be a route to amphiphilic copolymers with an original architecture. [less ▲]

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See detailContribution of "click" chemistry to the functionalization of aliphatic polyesters
Schmeits, Stephanie ULg; Riva, Raphaël ULg; Zednik, Jiri et al

Poster (2007, August 31)

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See detailMacromolecular engineering of aliphatic polyesters based on macrocyclic units
Lecomte, Philippe ULg; Li, Haiying; Riva, Raphaël ULg et al

Poster (2007, August 31)

The last decades have witnessed a steadily increasing progress in the macromolecular engineering of the main families of synthetic polymers. Ring-shaped copolymers show a unique topology due to the ... [more ▼]

The last decades have witnessed a steadily increasing progress in the macromolecular engineering of the main families of synthetic polymers. Ring-shaped copolymers show a unique topology due to the absence of any chain-end and exhibit distinct properties from their linear counterparts, such as glass transition temperature, order-disorder transition, reduced viscosity, lower hydrodynamic volumes. This communication aims at reporting on a novel route to biodegradable cyclic polyesters. Our strategy is based on the work of Prof. Kricheldorf who initiated the ring-opening polymerization of ε-caprolactone by cyclic tin dialkoxides, e.g., 2,2-dibutyl-2-stanna-1,3-dioxepane (DSDOP) in order to obtain “living” macrocyclic PCL, still containing two endocyclic tin-oxygen bonds. In this work, the resumption of polymerization by a few units of ε-caprolactone substituted by an acrylic unit, e.g., 1-(2-oxooxepan-3-yl)ethyl prop-2-enoate, followed by intramolecular photo-cross-linking of pendant unsaturations and finally by hydrolysis gave rise to macrocyclic PCL. As a rule, this strategy is very well-suited for the synthesis of high molecular weight PCL. Moreover, tin alkoxides were kept untouched after the cross-linking step and remained thus available for further macromolecular engineering. The process was extended to the synthesis of other architectures such as sun-shaped, two-tail tadpole-shaped, eight-shaped and symmetrical four-tail eight-shaped copolyesters. [less ▲]

Detailed reference viewed: 27 (5 ULg)