Yves Gnanou

French National Centre for Scientific Research, Lutetia Parisorum, Île-de-France, France

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Publications (167)410.27 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The chemistry of N-heterocyclic carbenes (NHCs) has witnessed tremendous development in the past two decades: NHCs have not only become versatile ligands for transition metals, but have also emerged as powerful organic catalysts in molecular chemistry and, more recently, in metal-free polymer synthesis. To understand the success of NHCs, this review first presents the electronic properties of NHCs, their main synthetic methods, their handling, and their reactivity. Their ability to activate key functional groups (e.g. aldehydes, esters, heterocycles, silyl ketene acetals, alcohols) is then discussed in the context of molecular chemistry. Focus has been placed on the activation of substrates finding analogies with monomers (e.g. bis-aldehydes, multi-isocyanates, cyclic esters, epoxides, N-carboxyanhydrides, etc.) and/or initiators (e.g. hydroxy- or trimethylsilyl-containing reagents) employed in such "organopolymerisation" reactions utilizing NHCs. A variety of metal-free polymers, including aliphatic polyesters and polyethers, poly(α-peptoid)s, poly(meth)acrylates, polyurethanes, or polysiloxanes can be obtained in this way. The last section covers the use of NHCs as structural components of the polymer chain. Indeed, NHC-based photoinitiators, chain transfer agents or functionalizing agents, as well as bifunctional NHC monomer substrates, can also serve for metal-free polymer synthesis.
    Chemical Society Reviews 01/2013; · 24.89 Impact Factor
  • Rachid Matmour, Yves Gnanou
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    ABSTRACT: This article reviews the various methods developed to generate di- and multicarbanionic lithiated initiators, the difficulties associated with their synthesis but also their potential in macromolecular engineering. It is shown that a wealth of complex macromolecular architectures based on monomers amenable to carbanionic polymerization can now be synthesized by divergent approach from these di- and multicarbanionic lithiated initiators. A comparison is made with other types of multifunctional initiators that have been developed from other living/controlled polymerizations, generating similar complex polymeric architectures from other monomers. A comparison is also made with the structures generated by the convergent carbanionic approach.
    Progress in Polymer Science. 01/2013; 38(1):30–62.
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    ABSTRACT: Anion metathesis of imidazol(in)ium chlorides with KHCO(3) afforded an easy one step access to air stable imidazol(in)ium hydrogen carbonates, denoted as [NHC(H)][HCO(3)]. In solution, these compounds were found to be in equilibrium with their corresponding imidazol(in)ium carboxylates, referred to as N-heterocyclic carbene (NHC)-CO(2) adducts. The [NHC(H)][HCO(3)] salts were next shown to behave as masked NHCs, allowing for the NHC moiety to be readily transferred to both organic and organometallic substrates, without the need for dry and oxygen-free conditions. In addition, such [NHC(H)][HCO(3)] precursors were successfully investigated as precatalysts in two selected organocatalyzed reactions of molecular chemistry and polymer synthesis, namely, the benzoin condensation reaction and the ring-opening polymerization of d,l-lactide, respectively. The generation of NHCs from [NHC(H)][HCO(3)] precursors occurred via the formal loss of H(2)CO(3)via a concerted low energy pathway, as substantiated by Density Functional Theory (DFT) calculations.
    Journal of the American Chemical Society 04/2012; 134(15):6776-84. · 10.68 Impact Factor
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    ABSTRACT: A free N-heterocyclic carbene has been efficiently used for the organocatalysed step-growthpolymerisation between aliphatic diisocyanates and diols. Both the nature of the diisocyanate monomer and the order of addition of reactants are critical parameters for the successful synthesis of soluble linear polyurethanes.
    Polym. Chem. 02/2012; 3(3):605-608.
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    ABSTRACT: Degradable dendrimer-like PEOs were designed using an original ABC-type branching agent featuring a cleavable ketal group, following an iterative divergent approach based on the anionic ring opening polymerization (AROP) of ethylene oxide and arborization of PEO chain ends. A seventh generation dendrimer-like PEO carrying 192 peripheral hydroxyls and exhibiting a molar mass of 446 kg · mol(-1) was obtained in this way. The chemical degradation of these dendritic scaffolds was next successfully accomplished under acidic conditions, forming linear PEO chains of low molar mass (≈2 kg · mol(-1)), as monitored by (1)H NMR, SEC, and MALDI-TOF mass spectrometry as well as by AFM.
    Macromolecular Rapid Communications 11/2011; 32(21):1722-8. · 4.93 Impact Factor
  • 09/2011: pages 249 - 293; , ISBN: 9783527631421
  • Michel Fontanille, Yves Gnanou
    09/2011: pages 7 - 55; , ISBN: 9783527631421
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    ABSTRACT: Unsaturated N-heterocyclic carbenes (NHCs) such as 1,3-bis(di-isopropyl)imidazol-2-ylidene (1) and 1,3-bis(di-tert-butyl)imidazol-2-ylidene (2) are shown to catalyze the sequential group transfer polymerization (GTP) of (meth)acrylic monomers. A variety of block copolymers including not only alkyl methacrylate but also alkyl acrylate monomer units as well as blocks deriving from N,N-dimethylacrylamide and methacrylonitrile were thus obtained at room temperature, using 1-methoxy-2-methyl-1-trimethylsiloxypropene (MTS) as initiator in THF as solvent. Block copolymerizations could be achieved, starting indifferently from the GTP of the acrylic monomer to that of the methacrylic one or vice versa, that is, regardless of the order of addition of the two monomers, in contrast to most examples of block copolymer synthesis by “controlled/living” sequential polymerization. It is postulated that these NHC-catalyzed GTPs of (meth)acrylics proceed via a single step concerted-like associative mechanism, involving the formation of thermodynamically unstable intermediates or transition states, likely hypervalent siliconates, with no detectable anionic enolates formed.
    Polym. Chem. 07/2011; 2(8):1706-1712.
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    ABSTRACT: In recent years it has become clear that the future of polymer chemistry and of the polymer industry lies more in improving existing polymers rather than discovering new monomers. Thus, the focus has now turned towards the synthesis of either novel or better controlled architectures through “living” polymerization mechanisms.
    07/2011: pages 189-224;
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    ABSTRACT: Janus-type dendrimer-like poly(ethylene oxide)s (PEOs) of 1st, 2nd, and 3rd generation carrying terminal hydroxyl functions on one side and cleavable ketal groups on the other were used as substrates to conjugate folic acid as a folate receptor and camptothecin (CPT) as a therapeutic drug in a sequential fashion. The conjugation of both FA and CPT was accomplished by “click chemistry” based on the 1,3 dipolar cycloaddition coupling reaction. First, the hydroxyl functions present at one face of Janus-type dendrimer-like PEOs were transformed into alkyne groups through a simple Williamson-type etherification reaction. Next, the ketals carried by the other face of the dendrimer-like PEOs were hydrolyzed, yielding twice as many hydroxyls which were subsequently subjected to an esterification reaction using 2-bromopropionic bromide. Before substituting azides for the bromide of 2-bromopropionate esters just generated in the presence of NaN3, an azido-containing amidified FA derivative was reacted through click chemistry with alkyne functions introduced on the other face of the dendrimer-like PEOs. A purposely designed alkyne-functionalized biomolecule derived from CPT was conjugated to the azido functions carried by the dendritic PEOs by a second “click reaction.” In this case, twice as many CPT as FA moieties were finally conjugated to the two faces of the Janus-type dendrimer-like PEOs, the numbers of folate and CPT introduced being 2 and 4, 4 and 8, and 8 and 16 for samples of 1st, 2nd, and 3rd generation, respectively (route A). An alternate route for functionalizing the dendrimer-like PEO of 1st generation consisted, first, in conjugating the azido-containing CPT onto the alkyne groups present on one face of the dendritic PEO scaffold. The alkyne-functionalized FA was further introduced by click chemistry after the bromides of 2-bromopropionate esters were chemically transformed into azido groups. The corresponding prodrug thus contains 2 CPT and 4 FA external moieties (route B). Every reaction step product was thoroughly characterized by 1H NMR spectroscopy. A preliminary investigation into the water solution properties of these functionalized dendritic PEOs is also presented. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
    Journal of Polymer Science Part A Polymer Chemistry 05/2011; 49(13):2839 - 2849. · 3.54 Impact Factor
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    ABSTRACT: ω-Norbornenyl polystyrene (PS) macromonomers whose molar masses range from 2700 to 11000 g/mole have been polymerized under living conditions by ring-opening metathesis, with a Schrock complex as initiator. The samples obtained have been characterized by a multiangle laser light scattering (MLLS) detector connected to the outlet of a size exclusion chromatography (SEC) instrument. The experimental values of the degree of polymerization (D̄Pn) lie in close agreement with the expected ones. The compactness of the various branched species formed, which covers a wide range of segment densities (ρS), is found to depend on two factors that are their degree of polymerization and the size of the initial macromonomer. The ratio (g) of the mean-square radii gyration (<R2b) of polymacromonomers to those (<R21) of linear PS homologues of same molar mass was also determined. Plotting the variation of g vs. the D̄Pn's of polymacromonomers gives an idea of the conformation adopted by these branched structures.
    Macromolecular Symposia 03/2011; 95(1):151 - 166.
  • Jean‐Luc Six, Yves Gnanou
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    ABSTRACT: Polymers with dendritic structure are a category of macromolecular architectures that has received considerable attention in the last decade. These polymers, also referred to as dendrimers, exhibit a degree of branching equal to unity. Interest in dendrimers whose branching points are linked to each other by generations of macromolecular size is in contrast quite new. This paper describes a new synthetic strategy which allows access to poly(ethylene oxide) (PEO) with dendritic structure. PEO dendrimers with different degree of compactness have been synthesized upon modifying the size of successive generations.
    Macromolecular Symposia 03/2011; 95(1):137 - 150.
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    ABSTRACT: This paper concerns the synthesis of two different structures of styrene-butadiene block copolymers that were respectively obtained via sequential and statistical ring-opening metathesis copolymerization of norbornene-terminated polystyrene (PS) and polybutadiene (PB) macromonomers. The stimulus for preparing such styrene-butadiene copolymers originates from the observation that phase-separated morphologies in block copolymers not only depend on the respective size of the blocks and the interaction parameter (χ), but also on the topological constraints introduced in the copolymer structure. From the differential scanning calorimetry study that was carried, it can be inferred that the two types of copolymers -prepared by sequential and statistical copolymerization of PS and PB macromonomers respectively- exhibit quite different phase separation behaviors, indicating that they develop distinct equilibrium domain morphologies.
    Macromolecular Symposia 03/2011; 128(1):21 - 37.
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    ABSTRACT: The synthesis of poly(N-heterocyclic carbene)s, denoted poly(NHC)s, and of their poly(NHC−CO2) adducts for a use in organocatalysis is described. Poly(NHC)s were readily obtained in a three-step sequence of reactions, involving i) the free-radical polymerization of ionic liquid monomers, that is, 1-vinyl-3-alkylimidazolium-type monomers with bromide (Br−) as counteranion, followed by ii) anion exchange of Br− for bis(trifluoromethanesulfonyl)imide (−NTf2), of the poly(1-vinyl-3-alkylimidazolium bromide) precursors, affording poly(1-vinyl-3-alkylimidazolium bis(trifluoromethanesulfonyl)imide) derivatives, and iii) deprotonation of the latter polymeric ionic liquids with a strong base. Carbon dioxide (CO2) was found to reversibly react with poly(NHC)s forming relatively air-stable and thermolabile poly(NHC−CO2) adducts. Both poly(NHC)s and their poly(NHC−CO2) adducts were used as polymer-supported organic catalysts and precatalysts, respectively, in transesterification and benzoin condensation reactions under homogeneous conditions. Both types of polymer-supported NHCs were recycled and used several times, but the manipulation of poly(NHC)s −like their molecular NHC analogues- was more complicated owing to their air and moisture sensitivity. In this regard, zwitterionic poly(NHC−CO2) adducts like their molecular NHC−CO2 analogues could be easier manipulated than their bare poly(NHC) counterparts, providing good to excellent yields even after several organocatalytic cycles, in particular toward the transesterification reaction.
    Macromolecules. 03/2011;
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    ABSTRACT: 1,3-Bis(di-isopropyl)imidazol-2-ylidene (1) and 1,3-bis(di-tert-butyl)imidazol-2-ylidene (2), which are N-heterocyclic carbenes (NHCs) are shown to catalyze the solution group transfer polymerization (GTP) of miscellaneous monomers in a controlled fashion at room temperature, in the presence of 1-methoxy-2-methyl-1-trimethylsiloxypropene (MTS) as initiator. The ability of seven distinct monomers, methyl methacrylate (MMA), tert-butyl acrylate (tBA), n-butyl acrylate (nBA), N,N-dimethylaminoethyl acrylate (DMAEA), N,N-dimethyl acrylamide (DMA), N,N-dimethylaminoethyl methacrylate (DMAEMA), and methacrylonitrile (MAN) to polymerize via GTP by NHC catalysis has been evaluated. The first-order kinetic plots, that is the evolution of ln[M]0/[M] versus time, systematically deviate from linearity, with the noticeable exception of GTP of DMA. A direct dependence of the rate of GTP on the concentration in MTS initiator is observed in the case of tBA carried out in THF, that is, the rate of polymerization increases with [MTS], with a first-order dependence on [MTS]. These results suggest the formation of hypervalent siliconate intermediates in NHC-induced GTP of acrylic monomers which proceeds via an associative mechanism. The nonlinear variation of ln[M]0/[M] with time in the terminal phase of the polymerization of both acrylates and methacrylates may be explained by the development of strong interactions between the NHC and pendant ester groups of poly(meth)acrylates, limiting the availability of the catalyst for chain end activation. In contrast, interactions between the NHC and amide-type units of poly(DMA) are unlikely, NHCs being not known as effective catalysts for transamidation reactions. A first-order kinetic plot with a linear variation of ln[M]0/[M] with time is thus observed for the NHC-catalyzed GTP of DMA.
    Macromolecules. 10/2010;
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    ABSTRACT: A N-heterocyclic carbene, namely, 1,3-bis-(diisopropyl)imidazol-2-ylidene either directly initiates or catalyzes the metal-free ring opening polymerization of neat propylene oxide at 50 degrees C, affording well-defined alpha,omega-heterodifunctionalized poly(propylene oxide) oligomers.
    Chemical Communications 05/2010; 46(18):3203-5. · 6.38 Impact Factor
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    ABSTRACT: The present study describes innovations in the ring-opening polymerization (ROP) of ethylene oxide (EO) using N-heterocyclic carbenes (NHCs) as organocatalysts, which enables the synthesis of α,ω-heterodifunctionalized poly(ethylene oxide)s (PEOs). Two representative NHC catalysts, namely, 1,3-bis(diisopropyl)imidazol-2-ylidene (1) and 1,3-bis(di-tert-butyl)imidazol-2-ylidene (2), were efficiently employed in conjunction with a variety of chain regulators of general structure NuE, where Nu and E are the nucleophilic and the electrophilic part, respectively, with E = H or SiMe3 (e.g., PhCH2OH, HC≡CCH2OH, N3SiMe3, and PhCH2OSiMe3). Catalytic amounts of the NHC (typically [NHC]/[NuE]/[EO] = 0.1/1/100 in moles) were indeed utilized to trigger the metal-free ROP of EO at 50 °C in dimethyl sulfoxide, allowing the polymerization to proceed to completion. In this way, PEOs of dispersities lower than 1.2 and molar masses perfectly matching the [EO]/[NuE] ratio were obtained, attesting to the controlled/living character of these NHC-catalyzed polymerizations. Characterization of α,ω-difunctionalized PEOs by combined techniques such as 1H NMR spectroscopy, MALDI-TOF mass spectrometry, and size exclusion chromatography confirmed the quantitative introduction of the nucleophilic moiety (Nu) and its electrophilic component (E = H or SiMe3) in the α- and ω-position of the PEO chains, respectively, and the formation of polymers with narrowly distributed molar masses. These results are discussed in the light of the existence of two possible mechanisms. The first one involves a direct attack of the NHC catalyst onto EO and the formation of a zwitterionic intermediate (activated monomer mechanism). The second possibility is the activation by the NHC of the E moiety of the NuE chain regulator first and then of the α-Nu,ω-OE PEO chain (activated chain end mechanism).
    Macromolecules 02/2010; · 5.93 Impact Factor
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    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    ChemInform 01/2010; 33(6).
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    ABSTRACT: Dendrimer-like poly(ethylene oxide)s (PEOs) were synthesized through a semicontinuous process based on the anionic ring-opening polymerization (AROP) of ethylene oxide (EO), followed by AROP of a mixture of glycidol (G) and propylene oxide (PO). Glycidol was used as branching agent generating two hydroxyl groups after ring-opening, whereas propylene oxide served to prevent the aggregation of the generated terminal alkoxides. A three-armed PEO star was first prepared through AROP of EO from 1,1,1-tris(hydroxymethyl)ethane as trifunctional precursor using dimethyl sulfoxide (DMSO) as solvent. After completion of EO polymerization and without isolating the PEO star precursor, G and PO (molar ratio 1:3) were added in the same batch to be polymerized either sequentially or randomly. This led to a three-armed PEO star with an average number of terminal hydroxyls per arm which depended on the number of G units inserted at PEO chain ends, as determined by 1H NMR spectroscopy. Growth of the second and the third generation of PEO could be achieved upon reiterating the same steps of AROP of EO and subsequent AROP of G and PO (arborization step) in one pot, affording dendrimer-like PEOs of generation 3 with moderately distributed but expected molar masses. In a variant of this strategy, G was copolymerized in the presence of allyl glycidyl ether during the arborization step in order to introduce allylic double bonds at the branching points of the dendrimer-like PEOs.
    Macromolecules. 10/2009;
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    ABSTRACT: The solution properties of IL-based block copolymers (IL BCs) of the type PAm-b-PIL-1Br, PMAA-b-PIL-2Br, and PMAA-b-PIL-3Br, where PIL, PAm and PMAA stand for polymeric ionic liquid, poly(acrylamide), and poly(methacrylic acid), respectively, are manipulated and made to self-assemble into nanoparticles in water or in organic media. This can be achieved not only by simply exchanging the bromide (Br−) counteranion of IL blocks for −N(SO2CF3)2, but also by the choice of a selective solvent or by methylation of the hydrophilic PMAA blocks into hydrophobic poly(methyl methacrylate) (PMMA) ones. Investigations into the behavior of self-assembled IL BCs aggregates by 1H NMR spectroscopy, light scattering and transmission electron microscopy evidence that anion or solvent exchange or chemical modification induce the formation of polymeric vesicles referred to as polymersomes, for IL BCs of hydrophilic mass fraction (f) of around 40. The size and shape of the self-assembled aggregates formed can be altered by changing the composition of the blocks or by a partial exchange of the anion. In addition, the anion sensitivity of these IL BCs occurs reversibly. For instance, anion exchange of the PIL block, from Br− to −N(SO2CF3)2 leads to a vesicular morphology consisting of −N(SO2CF3)2-based IL blocks as the hydrophobic membrane stabilized by water-soluble PAm (or PMAA). As for PAm135-b-(PIL-1N(SO2CF3)2)12 IL BC possessing a hydrophilic mass fraction higher than 45, it is found to self-assemble into spherical polymeric micelles.
    Macromolecules 07/2009; 42(14):5167-5174. · 5.93 Impact Factor

Publication Stats

2k Citations
410.27 Total Impact Points

Institutions

  • 1998–2013
    • French National Centre for Scientific Research
      Lutetia Parisorum, Île-de-France, France
  • 1996–2012
    • Université Bordeaux 1
      • UMR LCPO - Laboratoire de Chimie des Polymères Organiques
      Talence, Aquitaine, France
  • 2010
    • Paul Sabatier University - Toulouse III
      Tolosa de Llenguadoc, Midi-Pyrénées, France
  • 2005–2007
    • University of Florida
      • Department of Chemistry
      Gainesville, FL, United States
  • 2003
    • Istanbul Technical University
      • Department of Chemistry
      İstanbul, Istanbul, Turkey
  • 2000–2002
    • University of Bordeaux
      Burdeos, Aquitaine, France
  • 2001
    • Laboratoire de Chimie de Coordination.
      Tolosa de Llenguadoc, Midi-Pyrénées, France
  • 1990
    • Cornell University
      Ithaca, New York, United States