François Stoffelbach

University of Liège, Luik, Walloon Region, Belgium

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Publications (39)141.94 Total impact

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    ABSTRACT: The polymerization of -caprolactone has been assessed in water using various Brönsted acids as catalysts. The reaction was found to be quantitative at 100°C, leading to number-average molecular weights up to 5000 g/mol. The Brönsted acid catalyzed polymerization of -caprolactone in water was further conducted in the presence of water-soluble polysaccharides thereby affording graft copolymers. The approach enables an easy, mild access to dextran hydroxyesters. For low degree of substitution, the latter self-assembles in water to form nanoparticles. Poly(ε-caprolactone)-graft-methylcellulose copolymers can also be obtained via a similar approach. It is noteworthy that the methodology reported herein is a one-step route to poly(ε-caprolactone)-graft-water-soluble polysaccharides, operating in mild conditions, i.e at low temperatures, using readily available metal-free catalysts and water as a solvent.
    Journal of Polymer Science Part A Polymer Chemistry 08/2014; 52(15):2139. · 3.54 Impact Factor
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    ABSTRACT: A new class of polymeric thermometers with a memory function is reported that is based on the supramolecular host–guest interactions of poly(N‐isopropylacrylamide) (PNIPAM) with side‐chain naphthalene guest moieties and the tetracationic macrocycle cyclobis(paraquat‐p‐phenylene) (CBPQT4+) as the host. This supramolecular thermometer exhibits a memory function for the thermal history of the solution, which arises from the large hysteresis of the thermoresponsive LCST phase transition (LCST=lower critical solution temperature). This hysteresis is based on the formation of a metastable soluble state that consists of the PNIPAM–CBPQT4+ host–guest complex. When heated above the transition temperature, the polymer collapses, and the host–guest interactions are disrupted, making the polymer more hydrophobic and less soluble in water. Aside from providing fundamental insights into the kinetic control of supramolecular assemblies, the developed thermometer with a memory function might find use in applications spanning the physical and biological sciences. A polymeric thermometer with a visual read‐out is based on the supramolecular interaction between a poly(N‐isopropylacrylamide) copolymer with naphthalene side chains and the tetracationic macrocycle cyclobis(paraquat‐p‐phenylene) tetrachloride. This supramolecular thermometer is (re)programmable and exhibits a memory for the thermal history of the solution.
    Angewandte Chemie 04/2014;
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    ABSTRACT: A new class of polymeric thermometers with a memory function is reported that is based on the supramolecular host–guest interactions of poly(N-isopropylacrylamide) (PNIPAM) with side-chain naphthalene guest moieties and the tetracationic macrocycle cyclobis(paraquat-p-phenylene) (CBPQT4+) as the host. This supramolecular thermometer exhibits a memory function for the thermal history of the solution, which arises from the large hysteresis of the thermoresponsive LCST phase transition (LCST=lower critical solution temperature). This hysteresis is based on the formation of a metastable soluble state that consists of the PNIPAM–CBPQT4+ host–guest complex. When heated above the transition temperature, the polymer collapses, and the host–guest interactions are disrupted, making the polymer more hydrophobic and less soluble in water. Aside from providing fundamental insights into the kinetic control of supramolecular assemblies, the developed thermometer with a memory function might find use in applications spanning the physical and biological sciences.
    Angewandte Chemie International Edition 04/2014; · 11.34 Impact Factor
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    ABSTRACT: A new class of polymeric thermometers with a memory function is reported that is based on the supramolecular host–guest interactions of poly(N-isopropylacrylamide) (PNIPAM) with side-chain naphthalene guest moieties and the tetracationic macrocycle cyclobis(paraquat-p-phenylene) (CBPQT4+) as the host. This supramolecular thermometer exhibits a memory function for the thermal history of the solution, which arises from the large hysteresis of the thermoresponsive LCST phase transition (LCST=lower critical solution temperature). This hysteresis is based on the formation of a metastable soluble state that consists of the PNIPAM–CBPQT4+ host–guest complex. When heated above the transition temperature, the polymer collapses, and the host–guest interactions are disrupted, making the polymer more hydrophobic and less soluble in water. Aside from providing fundamental insights into the kinetic control of supramolecular assemblies, the developed thermometer with a memory function might find use in applications spanning the physical and biological sciences.
    Angewandte Chemie 04/2014;
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    ABSTRACT: A well-defined cyclobis(paraquat-p-phenylene) (CBPQT4+) end-functionalized poly(n-butyl acrylate) 3 was prepared via RAFT polymerization using a new trithiocarbonate CBPQT4+ derivative 2 as a reversible chain transfer agent. We have shown that the electron-poor CBPQT4+ moiety at the α-chain-end could be specifically modified by complex formation with various functionalized macromolecules featuring complementary electron rich end groups, thereby leading to the corresponding supramolecular diblock copolymers. The latter could be conveniently disassembled upon heating, by applying electrochemical redox processes or by the addition of a competing molecular guest. Furthermore, we can generate new diblock architectures upon the addition of an appropriately functionalized polymer. We also describe preliminarily results regarding the formation of nanostructured architectures both in solution and in thin films.
    Polym. Chem. 12/2013; 5(3).
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    ABSTRACT: A well-defined poly(N-isopropyl acrylamide) 1 incorporating at one termini a cyclobis(paraquat-p-phenylene) (CBPQT(4+) ) recognition unit is prepared via a RAFT polymerization followed by a copper-catalyzed azide-alkyne cycloaddition (CuAAC). (1) H NMR (1D, DOSY), UV-vis and ITC experiments reveal that polymer 1 is able of forming effective host-guest complexes with tetrathiafulvalene (TTF) end-functionalized polymers in water, thereby leading to the formation of non-covalently-linked double-hydrophilic block copolymers. The effect of the temperature on both the LCST phase transition of 1 and its complexes and on CBPQT(4+) /TTF host-guest interactions is investigated.
    Macromolecular Rapid Communications 12/2013; · 4.93 Impact Factor
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    ABSTRACT: The controlled/living free-radical copolymerization of vinylidene chloride (VDC) with methyl acrylate (MeA) or acrylic acid (AA) was studied by the reversible addition–fragmentation chain transfer (RAFT) technique using a trithiocarbonate RAFT agent. The reactions were performed in 1,4-dioxane solution at 30 °C and led to good control and high chain-end functionality. P(VDC-co-MeA)-b-PAA, PAA-b-P(VDC-co-MeA), and PAA-b-P(VDC-co-AA) amphiphilic block copolymers were then prepared in the same conditions, starting either from a hydrophobic P(VDC-co-MeA) macromolecular RAFT (macro-RAFT) agent or from a hydrophilic PAA one. The advantage of the first synthesis pathway relies on the very good transfer efficiency to trithiocarbonate-ended P(VDC-co-MeA) and on the rapid consumption of the latter even when low percentages (10 mol %) of MeA comonomer are incorporated in the macro-RAFT agent. In contrast, for the second approach a rapid consumption of the macro-RAFT agent is only reached with 30 mol % of MeA in the comonomer feed, whereas with 10 mol % of MeA the transfer constant was determined to be only close to 1. Finally, we demonstrated that PAA-b-P(VDC-co-AA) diblock copolymers might also be obtained with controlled features in a one-pot process.
    Macromolecules 02/2013; 46(3):664-673. · 5.93 Impact Factor
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    ABSTRACT: An ionically connected polystyrene-block-poly(ethylene oxide) diblock copolymer (PS−+PEO) has been prepared by blending a PEO block functionalized by a dimethylamino group at one extremity with a sulfonic acid terminated PS block. Proton transfer occurs from the sulfonic acid to the dimethylamino group, resulting in the formation of an ion pair acting as a junction between the two polymer blocks. This copolymer was further used to prepare thin films with a cylindrical morphology consisting of PEO cylinders embedded in a PS matrix and oriented perpendicularly to the film surface. Nanoporous thin films with sulfonate groups on the pore walls have been finally obtained after solvent extraction of the PEO microphases. The presence of those sulfonate groups was evidenced by grafting a positively charged fluorescent dye on the pore walls.
    European Polymer Journal 05/2012; 48(5):940–944. · 3.24 Impact Factor
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    ABSTRACT: It is well-established that a competitive adsorption exists between polycarboxylate superplasticizers (SP) and sulfate ions solubilized in the interstitial solution of cement paste, which may cause a loss of the dispersing properties. This has been explained by competitive weak ionic interactions between functional carboxyl groups and sulfate ions with cement grains. In this study, SPs including trialkoxysilane functional groups have been synthesized. Adsorption and dispersing properties of these SPs were evaluated in the presence of different concentrations of Na2SO4 added in aqueous solution. It appeared that a partial substitution of carboxyl groups by trialkoxysilane in the polymer makes them more resistant to sulfate ions. We suggested that the high adsorption capacity of these SPs results from the formation of strong bonds between hydroxysilane groups and calcium silicate hydrate phases. The improved compatibility of these new silylated SPs has been demonstrated through the formulation of two different concrete equivalent mortars.
    Cement and Concrete Research 01/2012; 42(1):166–172. · 3.11 Impact Factor
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    ABSTRACT: The aqueous solution properties of amphiphilic tetrathiafulvalene (TTF) end-functionalized poly(N-isopropylacrylamide) (PNIPAM) derivative 1 have been studied. Fluorescence spectroscopy, dynamic light scattering (DLS) and differential scanning calorimetry (Nano-DSC) were used to monitor the temperature-induced micellization and showed that 1 underwent two successive phase transitions corresponding to unimer-to-micelle and lower critical solution temperature (LCST) transitions, respectively. We have investigated the complexation properties of the TTF unit toward cyclobis(paraquat-p-phenylene) (CBPQT4+) or the randomly methylated β-cyclodextrin (RAMEB) to manipulate the amphiphilicity of 1 and to control the unimer-to-micelle phase transition by forming pseudorotaxane-like architectures. For the RAMEB complex with 1, the addition of a competitive guest such as 1-adamantanol resulted in the restoration of amphiphilicity of polymer 1 and consequently the reformation of micelles.
    Macromolecules. 07/2011; 44(16).
  • Claire Bernhardt, François Stoffelbach, Bernadette Charleux
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    ABSTRACT: A new alkene-functionalized SG1-based alkoxyamine was synthesized and used to prepare well-defined functional polymers by nitroxide mediated polymerization. The latter were characterized by NMR, SEC and MALDI-TOF mass spectrometry. Livingness was assessed by chain extension toward AB-type block copolymer. The alkene functionality located at the α-chain-end allowed the post-modification of the polymer by thiol–ene coupling reaction.
    Polym. Chem. 12/2010; 2(1):229-235.
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    ABSTRACT: In this article, we report the formation of micelles from a tetrathiafulvalene (TTF) end-functionalized poly(N-isopropylacrylamide) (poly(NIPAM)) derivative (1). We have determined the critical aggregation concentration (CAC) and average diameter of the micelles using fluorescence spectroscopy and dynamic light scattering experiments, respectively. We have exploited the NIPAM backbone of the polymer to thermally transform the swollen hydrophilic poly(NIPAM) derivative to a more globular hydrophobic state at the lower critical solution temperature (LCST). Finally, we have shown that we can exploit the chemical oxidation and complexation properties of the TTF unit to disrupt the micelle architecture to release the hydrophobic dye Nile Red from the interior of the micelle.
    Journal of the American Chemical Society 08/2010; 132(31):10796-801. · 10.68 Impact Factor
  • Jutta Rieger, Wenjing Zhang, François Stoffelbach, Bernadette Charleux
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    ABSTRACT: Water-soluble poly(N,N-dimethylacrylamide)s (PDMAAm) with a reactive trithiocarbonate group exhibiting different structures were used as macromolecular RAFT (reversible addition−fragmentation chain transfer) agents in the surfactant-free emulsion polymerization of n-butyl acrylate and styrene, under ab initio, batch conditions. Independently of the structure of the RAFT group, the polymerizations were fast and controlled with molar masses that matched well the theoretical values and rather low polydispersity indexes. Monomer conversions close to 100% were reached and the polymerizations behaved as controlled systems, even when solids contents up to 40% were targeted. The system thus led to poly(N,N-dimethylacrylamide)-b-poly(n-butyl acrylate) and poly(N,N-dimethylacrylamide)-b-polystyrene amphiphilic diblock copolymers formed in situ and self-assembled upon chain extension. The stability of the aqueous dispersions, measured by the amount of coagulum formed, improved with increasing length of the stabilizing hydrophilic PDMAAm segments.
    Macromolecules. 07/2010; 43(15).
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    ABSTRACT: The reversible addition−fragmentation chain transfer (RAFT) polymerization technique has been employed to synthesize various linear tetrathiafulvalene end-functionalized polymers. n-Butyl acrylate, N-isopropylacrylamide, and styrene monomers were polymerized in the presence of azobis(isobutyronitrile) and a new tetrathiafulvalene (TTF) trithiocarbonate derivative as reversible chain transfer agent. All RAFT polymerizations exhibited pseudo-first-order kinetics, a linear increase of the number-average molar mass (Mn SEC) with conversion and narrow molar mass distributions (polydispersity <1.3). The resulting homopolymers exhibited α-TTF and ω-trithiocarbonyl end groups. Cyclic voltammetry was used to investigate the electrochemical properties of the TTF polymers. Finally, we have shown that the TTF moiety at the α-chain-end could be specifically modified by complex formation with the tetracationic cyclophane cyclobis(paraquat-p-phenylene) (CBPQT4+) in organic media. Electrochemical oxidation of the TTF moiety resulted in disassembly of the polymer inclusion complex (PIC).
    11/2009;
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    ABSTRACT: We describe the application of the LCST of a naphthalene-functionalised polyNIPAM derivative as a convenient, tuneable and reversible method to disrupt complex formation with CBPQT(4+) in water.
    Chemical Communications 10/2009; · 6.38 Impact Factor
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    ABSTRACT: The RAFT-mediated, surfactant-free, ab initio, batch emulsion polymerization of n-butyl acrylate (nBA) and its copolymerization with methyl methacrylate (MMA) were studied. The control agent was a surface-active trithiocarbonate macromolecular RAFT agent composed of a hydrophilic poly(ethylene oxide) (PEO) block and a hydrophobic dodecyl chain. The homopolymerizations of nBA were fast with high final conversions, and the polymer chains were well-controlled with narrow molar mass distribution. The length of the PEO chain was shown to affect the particle size and the polymerization kinetics directly. We found the conditions to tune the particle size independently from the poly(n-butyl acrylate) chain length by playing with a mixture of macro-RAFT agents with long and short PEO segment or by adding a PEO-based nonionic surfactant. The copolymerizations of nBA and MMA exhibited features very similar to those of the nBA homopolymerizations provided that the molar percentage of MMA did not exceed approximately 75%. In all cases, stable, submicrometric particles composed of amphiphilic diblock copolymer chains were formed.
    Macromolecules 08/2009; 42(15). · 5.93 Impact Factor
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    ABSTRACT: Functionalized poly-epsilon-caprolactone-block-polyethyleneglycol (PCL-PEG) amphiphilic copolymers were prepared to be constituents of nanocarriers used for the targeting of specific cells. Hence, we conceived a smooth and simple photografting methodology on these copolymers using a bifunctional molecular clip (O-succinimidyl-4-(p-azido-phenyl)butanoate). We prepared PCL-PEGs with pendent N-hydroxysuccinimide esters and studied the grafting with 3H-lysine, which radioactivity was counted by LSC. Several parameters were investigated, such as behavior of homopolymers, initial concentrations, irradiation, and incubation durations. Evidences of a "PEG directed photografting" are discussed and this selectivity could be improved by a selective solvent technique. The photografting on different PCL-PEGs revealed a dependency of the rates to the crystallinity of the copolymers. Several controls by SEC, DLS, and TEM of the treated copolymers were realized. Lastly, the coupling of alpha-D-mannopyranoside ligand was performed, reaching amounts of 5400 nmol/g of PCL-PEG. This derivatized PCL-PEG enters in the preparation of nanocarriers used for the targeting of antigen presenting cells.
    Biomacromolecules 03/2009; 10(4):966-74. · 5.37 Impact Factor
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    ABSTRACT: This communication describes the first example of the efficient use of a simple amphiphilic molecule as both a surfactant and an initiator in the miniemulsion polymerization of methyl methacrylate under AGET and ARGET ATRP conditions.
    Chemical Communications 11/2008; · 6.38 Impact Factor
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    ABSTRACT: The purpose of this paper was to study the application of a surface-active trithiocarbonate RAFT agent, the 2-(dodecylthiocarbonothioylthio)-2-methylpropanoic acid, sodium salt (TTCA) in surfactant-free, ab initio, batch emulsion polymerization. Because of the highly water-soluble character of the leaving group favoring exit from the micelles or the particles over reinitiation, the polymerization of styrene was completely inhibited. In contrast, the polymerization of n-butyl methacrylate was fast and led to small, stable particles, demonstrating the good stabilizing efficiency of TTCA. However, the control over molar mass was not effective, as homopolymers with high molar mass were formed. This was related to the inappropriate leaving/initiating group and low chain transfer constant of the RAFT agent in the free-radical polymerization of methacrylic esters and was also observed in bulk. This poor efficiency was overcome by copolymerizing n-butyl methacrylate with a low percentage of styrene or n-butyl acrylate. In this case, the bulk copolymerization led to controlled copolymers with predicted molar mass and narrow molar mass distribution and the chain transfer efficiency was similarly high in surfactant-free emulsion polymerization. The good colloidal characteristics of the latexes with the stabilizing group attached at the chain-end were maintained, leading to autostabilized latexes with small particle diameter, below 150 nm. This work is the first example of the direct and efficient use of a surface-active, low molar mass, RAFT agent in emulsifier-free, batch emulsion polymerization, leading simultaneously to a good control over molar mass and narrow molar mass distribution, together with good colloidal properties.
    Macromolecules. 10/2008; 41(21).
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    ABSTRACT: Amphiphilic block copolymers poly(ethylene oxide)-b-polystyrene (PEO-PS-Br) with various molecular weights and poly(ethylene oxide) homopolymer (PEO-Br) were synthesized and used as macroinitiators and stabilizers (reactive “surfactants”) for activator generated by electron transfer atom transfer radical polymerization (AGET ATRP) of n-butyl acrylate (BA), in miniemulsion either with or without ethyl 2-bromoisobutyrate (EBiB) as co-initiator. Under both conditions, the reactions were well controlled and stable latexes were formed. In the absence of EBiB, polymer particles with diameter around 120−230 nm were obtained, and the particles contained polymers with molecular weight Mn = 16 000−25 000 g/mol and relatively low polydispersity (Mw/Mn = 1.2−1.4). In the presence of a low molecular weight initiator, EBiB, the amount of surfactant used can be reduced in the reaction (1.7−4 wt % vs monomer). The percent of initiating sites from EBiB was changed from 30% to 90%, and the majority of the obtained polymers were initiated by EBiB. Nevertheless, because of the covalent linking of the surfactants to polymer chains, no free surfactant was left in the reaction system. The final diameter of latexes stabilized by reactive surfactants was around 200−390 nm, the number-average molecular weight Mn of the polymers obtained was 10 000−25 000 g/mol, and the polydispersity index was around 1.2.
    Macromolecules. 08/2008; 41(17).

Publication Stats

324 Citations
141.94 Total Impact Points

Institutions

  • 2006–2012
    • University of Liège
      • Center for Education and Research on Macromolecules (CERM)
      Luik, Walloon Region, Belgium
    • Leibniz Institute of Polymer Research Dresden
      • Max Bergmann Center for Biomaterials
      Dresden, Saxony, Germany
  • 2010
    • University of Lille Nord de France
      Lille, Nord-Pas-de-Calais, France
  • 2008–2010
    • Pierre and Marie Curie University - Paris 6
      • Laboratoire de Chimie des Polymères
      Lutetia Parisorum, Île-de-France, France
  • 2009
    • Université des Sciences et Technologies de Lille 1
      Lille, Nord-Pas-de-Calais, France
  • 2001–2007
    • University of Burgundy
      Dijon, Bourgogne, France
  • 2005
    • Laboratoire de Chimie de Coordination.
      Tolosa de Llenguadoc, Midi-Pyrénées, France
  • 2003
    • The University of Warwick
      • Department of Chemistry
      Coventry, England, United Kingdom