denis bertin - Academia.edu (original) (raw)

Papers by denis bertin

Research paper thumbnail of Design of membranes with controlled porosity and interfacial properties using self organisation of block copolymers

Research paper thumbnail of Design of blue or yellow emitting devices controlled by the deposition process of a cationic iridium (III) complex

Synthetic Metals, 2011

A phosphorescent cyclometalated heteroleptic Ir(III) complex was investigated as emitter for ligh... more A phosphorescent cyclometalated heteroleptic Ir(III) complex was investigated as emitter for lightemitting electrochemical cells (LECs) and polymer organic light-emitting diodes (POLEDs). By exploring the deposition conditions of the emissive layer in multilayered electroluminescent devices, we directly impacted the emission color by mixing or not the complex with poly(vinylcarbazole) (PVK). Strategy of emission color tuning enabled to produce blue or yellow emitting devices. Heteroleptic complex was characterized by UV-visible absorption and luminescence spectroscopy. Cyclic voltammetry and DFT calculations were also performed.

Research paper thumbnail of Purification, synthesis and characterization of AaCtx, the first chlorotoxin-like peptide from Androctonus australis scorpion venom

Peptides, 2011

AaCtx is the first chlorotoxin-like peptide isolated from Androctonus australis scorpion venom. I... more AaCtx is the first chlorotoxin-like peptide isolated from Androctonus australis scorpion venom. Its amino acid sequence shares 70% similarity with chlorotoxin from Leiurus quinquestriatus scorpion venom, from which it differs by twelve amino acids. Due to its very low concentration in venom (0.05%), AaCtx was chemically synthesized. Both native and synthetic AaCtx were active on invasion and migration of human glioma cells. However, their activity was found to be lower than that of chlorotoxin. The molecular model of AaCtx shows that most of amino acids differing between AaCtx and chlorotoxin are localized on the N-terminal loop and the α-helix. Based on known compounds that block chloride channels, we suggest that the absence of negative charged amino acids on AaCtx structure may be responsible for its weak activity on glioma cells migration and invasion. This finding serves as a starting point for structure-function relationship studies leading to design high specific anti-glioma drugs.

Research paper thumbnail of Lebetin Peptides: Potent Platelet Aggregation Inhibitors

Pathophysiology of Haemostasis and Thrombosis, 2001

Lebetins from Macrovipera lebetina snake venom constitute a new class of inhibitors of platelet a... more Lebetins from Macrovipera lebetina snake venom constitute a new class of inhibitors of platelet aggregation. There are two groups of peptides: lebetin 1 (L1; 11- to 13-mer) and lebetin 2 (L2; 37- to 38-mer). The short lebetins are identical to the N-terminal segments of the longer ones. They inhibit platelet aggregation induced by various agonists (e.g. thrombin, PAF-acether or collagen). The shortest lebetin (11-mer) shows potent inhibition of rabbit (IC50 = 7 nM) and human (IC50 = 5 nM) platelets. They prevent collagen-induced thrombocytopenia in rats. N- and C-terminal-truncated synthetic L1γ (sL1γ; 11-mer) is less active in inhibiting platelet aggregation than the native peptide. Results from Ala scan studies of the sL1γ peptide indicated that replacement of the residues (P3, G7, P8, P9 or N10) resulted in a remarkable drop in the activity, whereas replacement of residues K2, P4 or K6 by Ala resulted in enhancement of the antiplatelet activity by at least 10-fold. To examine the...

Research paper thumbnail of Cationic iridium complex for the design of soft salt-based phosphorescent OLEDs and color-tunable light-emitting electrochemical cells

Organic Electronics, 2011

Phosphorescent Organic Light-Emitting Diodes (PhOLEDs) based on iridium (III) soft salt were desi... more Phosphorescent Organic Light-Emitting Diodes (PhOLEDs) based on iridium (III) soft salt were designed and studied. Heteroleptic anionic iridium complex (A) was prepared with thiocyanate anions and cationic iridium complex (C) was synthesized with 4,4 0-dinonyl-2,2 0-byridine as the ancillary ligand. Electronic and spectroscopic properties of the resulting combination of soft salt CÁA were investigated by mean of UV-visible absorption, fluorescence spectroscopy and cyclic voltammetry. DFT calculations were also performed and the electroluminescent performances evaluated. Light-emitting electrochemical cells (LECs) displaying color-variable emission were also obtained. This color tunability aroused from a modification of the molecular packing of the emissive layer with the temperature.

Research paper thumbnail of Single-ion BAB triblock copolymers as highly efficient electrolytes for lithium-metal batteries

Nature Materials, 2013

Electrochemical energy storage is one of the main societal challenges of this century. The perfor... more Electrochemical energy storage is one of the main societal challenges of this century. The performances of classical lithium-ion technology based on liquid electrolytes have made great advances in the past two decades, but the intrinsic instability of liquid electrolytes results in safety issues. Solid polymer electrolytes would be a perfect solution to those safety issues, miniaturization and enhancement of energy density. However, as in liquids, the fraction of charge carried by lithium ions is small (<20%), limiting the power performances. Solid polymer electrolytes operate at 80 • C, resulting in poor mechanical properties and a limited electrochemical stability window. Here we describe a multifunctional single-ion polymer electrolyte based on polyanionic block copolymers comprising polystyrene segments. It overcomes most of the above limitations, with a lithium-ion transport number close to unity, excellent mechanical properties and an electrochemical stability window spanning 5 V versus Li + /Li. A prototype battery using this polyelectrolyte outperforms a conventional battery based on a polymer electrolyte.

Research paper thumbnail of Direct synthesis of mesoporous silica presenting large and tunable pores using BAB triblock copolymers: Influence of each copolymer block on the porous structure

Microporous and Mesoporous Materials, 2008

Mesoporous silicas with large and tunable (from 4 to 40 nm) accessible pores have been successful... more Mesoporous silicas with large and tunable (from 4 to 40 nm) accessible pores have been successfully synthesized using laboratorymade BAB (A: hydrophilic block, B: hydrophobic block) type triblock copolymers as templates. A direct synthesis is carried out in the absence of swelling agent and without any further treatment. The polystyrene-b-poly(ethylene oxide)-b-polystyrene (PS-b-PEOb-PS) copolymers were synthesized using living/controlled radical polymerization. The porous structure (mesopore size, size distribution and microporous volume) was characterized using electron transmission microscopy and nitrogen sorption measurements. This study is focused on the control of the porous structure as a function of the hydrophobic PS block length and the hydrophilic block length (whilst keeping the other block length constant). It was found that when the PS block length increases: (i) the mesopore size increases linearly with PS block length which thus proffers a fine tuning of the pore diameter from 4 to 40 nm, (ii) the micropore volume decreases. When the PEO block length increases, (i) the mesopore size decreases (ii) the micropore volume increases. All these results were explained considering (i) that both PS and PEO block lengths have an influence on the degree of stretching of the PS chains, thus on the micellar core radius (ii) that the mesopore size is directly connected to the micellar core radius, i.e. that PEO chains do not directly participate to mesoporosity (due to its particular loop configuration) but only to microporosity.

Research paper thumbnail of Photo-Cross-Linked Diblock Copolymer Micelles: Quantitative Study of Photochemical Efficiency, Micelles Morphologies and their Thermal Behavior

Macromolecules, 2014

ABSTRACT Amphiphilic block copolymers based on azido-functional polystyrene (PVBA) and hydrophili... more ABSTRACT Amphiphilic block copolymers based on azido-functional polystyrene (PVBA) and hydrophilic poly(ethylene oxide) (PEO) have been synthesized by nitroxide mediated polymerization and used to prepare aqueous spherical micelles. These micelles consisting of a PEO corona and a PVBA core were stabilized by cores cross-linking under UV irradiation without addition of photoreagent. The efficiency of the core cross-linking was estimated in term of the conversion of azide groups to dibenzyldiazene junctions with liberation of gaseous nitrogen molecules. The micellar structures were studied by dynamic light scattering (DLS) and atomic force microscopy (AFM). Differential scanning calorimetry (DSC) was used to characterize the thermal behavior of freeze-dried micelles. Attachment of PEO block to a rigid core modified considerably the thermal behavior of PEO. We observed a decrease of about 15 °C for the crystallization temperature and 50% for the degree of crystallinity of cross-linked micelles submitted to 45 min UV irradiation compared to pristine copolymer.

Research paper thumbnail of Characterization of Functional Poly(ethylene oxide)s and Their Corresponding Polystyrene Block Copolymers by Liquid Chromatography under Critical Conditions in Organic Solvents

Macromolecules, 2012

Separation of functional poly(ethylene oxide) PEO and PEO block copolymers was investigated using... more Separation of functional poly(ethylene oxide) PEO and PEO block copolymers was investigated using liquid chromatography under critical conditions (LCCC) with a mixture of organic solvents as eluent. The optimum eluent is a mixture of 58.05% chloroform, 6.45% methanol, and 35.50% n-heptane (v/v/v) using a reverse phase (C 8) column. Unlike what was expected, the elution mechanism is governed by the interaction of a polar endgroup with the column. In these conditions, poly(ethylene oxide) (PEO) functionalized with either an acrylate or alkoxyamine moieties were separated. This allows us to investigate the efficiency of the synthesis of poly(ethylene oxide)-b-polystyrene (PEO-b-PS) and polystyrene-b-poly(ethylene oxide) b-polystyrene (PS-b-PEO-b-PS) block copolymers prepared via the combination of 1,2 radical intermolecular addition followed by the nitroxide-mediated polymerization NMP of styrene. Amphiphilic diblock PEO-b-PS and triblock PS-b-PEO-b-PS copolymers were also separated from PEO homopolymers using the same experimental conditions. We showed that the PEO block is then invisible, and the calibration curve obtained using PS homopolymer standards could be used to determine the whole molar mass of the PS block in block copolymers with PS and PEO segments, with a weak influence of the architecture.

Research paper thumbnail of Polyaromatic Structures as Organo-Photoinitiator Catalysts for Efficient Visible Light Induced Dual Radical/Cationic Photopolymerization and Interpenetrated Polymer Networks Synthesis

Macromolecules, 2012

All reagents were purchased from Aldrich or Alfa Aesar and used as received without further purif... more All reagents were purchased from Aldrich or Alfa Aesar and used as received without further purification. Mass spectroscopy was performed by the Spectropole of Aix-Marseille University (Marseille). The HRMS mass spectral analysis was performed with a QStar Elite (Applied Biosystems SCIEX) mass spectrometer. ESI-HRMS measurements were also carried out with a Waters Xevo-QTOF. 1 H and 13 C NMR spectra were determined at room temperature in 5 mm o.d. tubes on a Bruker Avance 400 spectrometer of the Spectropole : 1 H (400 MHz) and 13 C (100 MHz). The 1 H chemical shifts were referenced to the solvent peak: CDCl 3 (7.26 ppm), and the 13 C chemical shifts were referenced to the solvent peak: CDCl 3 (77.0 ppm). The CPMAS and HPDEC spectra were recorded with a spectrometer operating at 10kHz (spinning rate). Purities higher than 90% for the three complexes were determined from the 1 H NMR spectra. Truxene and tribromotruxene were prepared according to a literature procedure. 1 Truxene derivative T_1 was synthesized in one step by a palladium-catalyzed Suzuki-cross coupling reaction between the commercially available pyrene-1-boronic acid and tribromohexahexyltruxene. Suzuki cross coupling occurred efficiently at reflux and under vigorous stirring of a water/toluene/ethanol biphasic mixture using potassium carbonate as base and Pd(PPh 3) 4 as catalyst. Tris(aza)pentacene T_2 was synthesized in one step by condensation of three equivalents of 2,3-diaminophenazine 2 with one equivalent of hexaketocyclohexane (see scheme 1).

Research paper thumbnail of A Step Towards High‐Molecular‐Weight Living/Controlled Polystyrene Using SG1‐Mediated Polymerization

Macromolecular Reaction Engineering, 2010

The synthesis of high‐molecular‐weight living/controlled polystyrene by NMP was studied. The comb... more The synthesis of high‐molecular‐weight living/controlled polystyrene by NMP was studied. The combination of Ac2O and alkoxyamines based on nitroxides TEMPO, TIPNO, and SG1 was tested at 130 °C. With TEMPO and TIPNO, dipole/dipole interactions led to a decrease in nitroxide concentration and an acceleration of the reaction. To minimize thermal auto‐initiation and thus obtain high‐$\overline M _{\rm n}$ PS, the temperature was lowered. At 90 °C, the use of BlocBuilder yielded PS of overlineMrmn\overline M _{\rm n}overlineMrmn = 210 000 g · mol−1 with a living fraction of 60%. Finally, new SG1‐based nitroxides were used to perform the polymerization at 75 °C. Since these nitroxides were too constrained, the decrease in kc caused a loss of control and livingness for high‐$\overline M _{\rm n}$ polymers.magnified image

Research paper thumbnail of Cover Picture: Macromol. Rapid Commun. 3/2006

Macromolecular Rapid Communications, 2006

Cover: The cover picture shows a strategy used to synthesize new functional polyethylenes (PE). A... more Cover: The cover picture shows a strategy used to synthesize new functional polyethylenes (PE). A neodymium based complex catalyzes ethylene chain growth reaction on MgR2 producing Mg(PE)2. Those are excellent candidates to react with disulfides of thiocarbonylated compounds (RC(S)SSC‐(S)R). Further details can be found in the Communication by R. Godoy Lopez, C. Boisson, F. D'Agosto,* R. Spitz, F. Boisson, D. Gigmes, and D. Bertin on page 173.

Research paper thumbnail of New Functional Polyolefins: Towards a Bridge Between Catalytic and RAFT Polymerizations?

Macromolecular Rapid Communications, 2006

Summary: Di‐polyethylenyl magnesium compounds, obtained by a transition metal catalyzed chain gro... more Summary: Di‐polyethylenyl magnesium compounds, obtained by a transition metal catalyzed chain growth reaction on butyloctyl magnesium, are reacted with a range of disulfides of thiocarbonylated compounds (RC(S)SSC(S)R). Xanthate, dithiocarbamate, dithioester, and trithiocarbonate‐functionalized polyethylenes are thus obtained and characterized by 1H NMR and IR spectroscopy, and MALDI TOF mass spectrometry. These macroRAFT agents may serve as building blocks for the synthesis of block copolymers based on polyolefins and polar segments.Thio thiocarbonylate‐terminated polyethylene chains are easily prepared in high yield by a two step reaction and analyzed by MALDI‐TOF mass spectrometry.imageThio thiocarbonylate‐terminated polyethylene chains are easily prepared in high yield by a two step reaction and analyzed by MALDI‐TOF mass spectrometry.

Research paper thumbnail of Random Copolymers with Pendant Cationic Mixed-Ligand Terpyridine-Based Iridium (III) Complexes: Synthesis and Application in Light-Emitting Devices

Macromolecular Chemistry and Physics, 2011

Research paper thumbnail of Poly(D,L-Lactide)-block-Poly(2-Hydroxyethyl Acrylate) Block Copolymers as Potential Biomaterials for Peripheral Nerve Repair: in vitro and in vivo Degradation Studies

Macromolecular Bioscience, 2011

Research paper thumbnail of Organized Formation of 2D Extended Covalent Organic Frameworks at Surfaces

Journal of the American Chemical Society, 2008

The development of nanoscale masking for particle deposition is exceedingly important to push the... more The development of nanoscale masking for particle deposition is exceedingly important to push the future of nanoelectronics beyond the current limits of lithography. We present the first example of ordered hexagonal covalent nanoporous structures deposited in extended arrays of near monolayer coverage across a Ag(111) surface. The networks were formed from the deposition of the reagents from a heated molybdenum crucible between 370 and 460 K under ultrahigh vacuum (UHV) onto a cleaned Ag(111) substrate and imaged using a scanning tunneling microscope (STM). Two surface covalent organic frameworks (SCOFs) are presented; the first is formed from the deposition of 1,4-benzenediboronic acid (BDBA) and its dehydration to form the boroxine-linked SCOF-1, the second is formed from the co-deposition of BDBA and 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP) to form a dioxaborole-linked SCOF-2 network. The networks were found to produce nanoporous structures of 15 A for SCOF-1 and 29 A for SCOF-2, which agreed with theoretical pore sizes determined from DFT calculations. Both SCOFs were found to have exceptional thermal stability, maintaining their structure until approximately 750 K, which was found to be the polymer degradation temperature from thermal gravimetric analysis (TGA).

Research paper thumbnail of Elaboration of densely functionalized polylactide nanoparticles from N -acryloxysuccinimide-based block copolymers

Journal of Polymer Science Part A: Polymer Chemistry, 2011

Poly(N-acryloxysuccinimide) (PNAS) and poly(Nacryloxysuccinimide-coN -vinylpyrrolidone) (P(NAS-co... more Poly(N-acryloxysuccinimide) (PNAS) and poly(Nacryloxysuccinimide-coN -vinylpyrrolidone) (P(NAS-co-NVP)) of adjustable molecular weights and narrow polydispersities were prepared by nitroxide-mediated polymerization (NMP) in N,Ndimethylformamide in the presence of free SG1 (N-tert-butyl-N-1-diethylphosphono-(2,2-dimethylpropyl) nitroxide), with MAMA-SG1 (N-(2-methylpropyl)-N-(1-diethylphosphono-2,2-dimethylpropyl)-O-(2-carboxylprop-2-yl)hydroxylamine) alkoxyamine as initiator. The reactivity ratios of NAS and NVP were determined to be r NAS ¼ 0.12 and r NVP ¼ 0, indicating a strong alternating tendency for the P(NAS-co-NVP) copolymer. NAS/ NVP copolymerization was then performed from a SG1-functionalized poly(D,L-lactide) (PLA-SG1) macro-alkoxyamine as initiator, leading to the corresponding PLA-b-P(NAS-co-NVP) block copolymer, with similar NAS and NVP reactivity ratios as mentioned above. The copolymer was used as a surface modifier for the PLA diafiltration and nanoprecipitation processes to achieve nanoparticles in the range of 450 and 150 nm, respectively. The presence of the functional/hydrophilic P(NAS-co-NVP) block, and particularly the N-succinimidyl (NS) ester moieties at the particle surface, was evidenced by ethanolamine derivatization and zeta potential measurements. V

Research paper thumbnail of Long‐range polar and steric effects in propionate‐SG1‐type alkoxyamines (SG1‐CHMeCOOX): a multiparameter analysis

Journal of Physical Organic Chemistry, 2006

The effects of the substituent X on the homolysis rate constants (kd) of SG1‐propionate type alko... more The effects of the substituent X on the homolysis rate constants (kd) of SG1‐propionate type alkoxyamines (SG1‐CHMeCOOX) are analyzed by a multiparametric equation with υ, the steric constant and σI, the polar inductive/field Hammett constant of X. An influence of long‐range polar and steric effects on kd was observed, that is, decrease in kd with increasing size of the X group and increase in kd with increasing polarity of the X group. Copyright © 2006 John Wiley & Sons, Ltd.

Research paper thumbnail of β-Fragmentation of alkoxyl radicals: Natural bond orbital analysis

International Journal of Quantum Chemistry, 2005

Alkoxyl radicals are often generated in order to perform regioselective hydrogen atom abstraction... more Alkoxyl radicals are often generated in order to perform regioselective hydrogen atom abstraction. However, their ␤-fragmentation generates alkyl radicals that are less efficient to abstract hydrogen atoms. We have performed density functional theory (DFT) calculations [UB3LYP/6-31ϩG(d,p)] followed by a natural bond orbital (NBO) analysis on a series of alkoxyl radicals. The ␤-fragmentation of these radicals is discussed in terms of bond population and hyperconjugative interactions.

Research paper thumbnail of Intramolecular Hydrogen Bonding: The Case of β‐Phosphorylated Nitroxide (= Aminoxyl) Radical

Helvetica Chimica Acta, 2006

Alkoxyamines and persistent nitroxide (= aminoxyl) radicals are important regulators of nitroxide... more Alkoxyamines and persistent nitroxide (= aminoxyl) radicals are important regulators of nitroxide‐mediated radical polymerization. Since polymerization times decrease with the increasing homolysis rate constant of the CON bond homolysis between the polymer chain and the aminooxy moiety, the factors influencing the cleavage rate constant are of considerable interest. It has already been shown that the value of the homolysis rate constant kd is very sensitive to the stabilization of both released radical species. X‐Ray, EPR, and kinetic data showed that the intramolecular H‐bonding radical in the 1‐(diethoxyphosphoryl)‐2,2‐dimethylpropyl 2‐hydroxy‐1,1‐dimethylethyl nitroxide (3a) (homologue of 2‐hydroxy‐1,1‐dimethylethyl 1‐phenyl‐2‐methylpropyl nitroxide (2a)) did not occur with the nitroxide moiety as expected but with the phosphoryl group. However, the polymerization rate of styrene (= ethenylbenzene) was significantly enhanced.

Research paper thumbnail of Design of membranes with controlled porosity and interfacial properties using self organisation of block copolymers

Research paper thumbnail of Design of blue or yellow emitting devices controlled by the deposition process of a cationic iridium (III) complex

Synthetic Metals, 2011

A phosphorescent cyclometalated heteroleptic Ir(III) complex was investigated as emitter for ligh... more A phosphorescent cyclometalated heteroleptic Ir(III) complex was investigated as emitter for lightemitting electrochemical cells (LECs) and polymer organic light-emitting diodes (POLEDs). By exploring the deposition conditions of the emissive layer in multilayered electroluminescent devices, we directly impacted the emission color by mixing or not the complex with poly(vinylcarbazole) (PVK). Strategy of emission color tuning enabled to produce blue or yellow emitting devices. Heteroleptic complex was characterized by UV-visible absorption and luminescence spectroscopy. Cyclic voltammetry and DFT calculations were also performed.

Research paper thumbnail of Purification, synthesis and characterization of AaCtx, the first chlorotoxin-like peptide from Androctonus australis scorpion venom

Peptides, 2011

AaCtx is the first chlorotoxin-like peptide isolated from Androctonus australis scorpion venom. I... more AaCtx is the first chlorotoxin-like peptide isolated from Androctonus australis scorpion venom. Its amino acid sequence shares 70% similarity with chlorotoxin from Leiurus quinquestriatus scorpion venom, from which it differs by twelve amino acids. Due to its very low concentration in venom (0.05%), AaCtx was chemically synthesized. Both native and synthetic AaCtx were active on invasion and migration of human glioma cells. However, their activity was found to be lower than that of chlorotoxin. The molecular model of AaCtx shows that most of amino acids differing between AaCtx and chlorotoxin are localized on the N-terminal loop and the α-helix. Based on known compounds that block chloride channels, we suggest that the absence of negative charged amino acids on AaCtx structure may be responsible for its weak activity on glioma cells migration and invasion. This finding serves as a starting point for structure-function relationship studies leading to design high specific anti-glioma drugs.

Research paper thumbnail of Lebetin Peptides: Potent Platelet Aggregation Inhibitors

Pathophysiology of Haemostasis and Thrombosis, 2001

Lebetins from Macrovipera lebetina snake venom constitute a new class of inhibitors of platelet a... more Lebetins from Macrovipera lebetina snake venom constitute a new class of inhibitors of platelet aggregation. There are two groups of peptides: lebetin 1 (L1; 11- to 13-mer) and lebetin 2 (L2; 37- to 38-mer). The short lebetins are identical to the N-terminal segments of the longer ones. They inhibit platelet aggregation induced by various agonists (e.g. thrombin, PAF-acether or collagen). The shortest lebetin (11-mer) shows potent inhibition of rabbit (IC50 = 7 nM) and human (IC50 = 5 nM) platelets. They prevent collagen-induced thrombocytopenia in rats. N- and C-terminal-truncated synthetic L1γ (sL1γ; 11-mer) is less active in inhibiting platelet aggregation than the native peptide. Results from Ala scan studies of the sL1γ peptide indicated that replacement of the residues (P3, G7, P8, P9 or N10) resulted in a remarkable drop in the activity, whereas replacement of residues K2, P4 or K6 by Ala resulted in enhancement of the antiplatelet activity by at least 10-fold. To examine the...

Research paper thumbnail of Cationic iridium complex for the design of soft salt-based phosphorescent OLEDs and color-tunable light-emitting electrochemical cells

Organic Electronics, 2011

Phosphorescent Organic Light-Emitting Diodes (PhOLEDs) based on iridium (III) soft salt were desi... more Phosphorescent Organic Light-Emitting Diodes (PhOLEDs) based on iridium (III) soft salt were designed and studied. Heteroleptic anionic iridium complex (A) was prepared with thiocyanate anions and cationic iridium complex (C) was synthesized with 4,4 0-dinonyl-2,2 0-byridine as the ancillary ligand. Electronic and spectroscopic properties of the resulting combination of soft salt CÁA were investigated by mean of UV-visible absorption, fluorescence spectroscopy and cyclic voltammetry. DFT calculations were also performed and the electroluminescent performances evaluated. Light-emitting electrochemical cells (LECs) displaying color-variable emission were also obtained. This color tunability aroused from a modification of the molecular packing of the emissive layer with the temperature.

Research paper thumbnail of Single-ion BAB triblock copolymers as highly efficient electrolytes for lithium-metal batteries

Nature Materials, 2013

Electrochemical energy storage is one of the main societal challenges of this century. The perfor... more Electrochemical energy storage is one of the main societal challenges of this century. The performances of classical lithium-ion technology based on liquid electrolytes have made great advances in the past two decades, but the intrinsic instability of liquid electrolytes results in safety issues. Solid polymer electrolytes would be a perfect solution to those safety issues, miniaturization and enhancement of energy density. However, as in liquids, the fraction of charge carried by lithium ions is small (<20%), limiting the power performances. Solid polymer electrolytes operate at 80 • C, resulting in poor mechanical properties and a limited electrochemical stability window. Here we describe a multifunctional single-ion polymer electrolyte based on polyanionic block copolymers comprising polystyrene segments. It overcomes most of the above limitations, with a lithium-ion transport number close to unity, excellent mechanical properties and an electrochemical stability window spanning 5 V versus Li + /Li. A prototype battery using this polyelectrolyte outperforms a conventional battery based on a polymer electrolyte.

Research paper thumbnail of Direct synthesis of mesoporous silica presenting large and tunable pores using BAB triblock copolymers: Influence of each copolymer block on the porous structure

Microporous and Mesoporous Materials, 2008

Mesoporous silicas with large and tunable (from 4 to 40 nm) accessible pores have been successful... more Mesoporous silicas with large and tunable (from 4 to 40 nm) accessible pores have been successfully synthesized using laboratorymade BAB (A: hydrophilic block, B: hydrophobic block) type triblock copolymers as templates. A direct synthesis is carried out in the absence of swelling agent and without any further treatment. The polystyrene-b-poly(ethylene oxide)-b-polystyrene (PS-b-PEOb-PS) copolymers were synthesized using living/controlled radical polymerization. The porous structure (mesopore size, size distribution and microporous volume) was characterized using electron transmission microscopy and nitrogen sorption measurements. This study is focused on the control of the porous structure as a function of the hydrophobic PS block length and the hydrophilic block length (whilst keeping the other block length constant). It was found that when the PS block length increases: (i) the mesopore size increases linearly with PS block length which thus proffers a fine tuning of the pore diameter from 4 to 40 nm, (ii) the micropore volume decreases. When the PEO block length increases, (i) the mesopore size decreases (ii) the micropore volume increases. All these results were explained considering (i) that both PS and PEO block lengths have an influence on the degree of stretching of the PS chains, thus on the micellar core radius (ii) that the mesopore size is directly connected to the micellar core radius, i.e. that PEO chains do not directly participate to mesoporosity (due to its particular loop configuration) but only to microporosity.

Research paper thumbnail of Photo-Cross-Linked Diblock Copolymer Micelles: Quantitative Study of Photochemical Efficiency, Micelles Morphologies and their Thermal Behavior

Macromolecules, 2014

ABSTRACT Amphiphilic block copolymers based on azido-functional polystyrene (PVBA) and hydrophili... more ABSTRACT Amphiphilic block copolymers based on azido-functional polystyrene (PVBA) and hydrophilic poly(ethylene oxide) (PEO) have been synthesized by nitroxide mediated polymerization and used to prepare aqueous spherical micelles. These micelles consisting of a PEO corona and a PVBA core were stabilized by cores cross-linking under UV irradiation without addition of photoreagent. The efficiency of the core cross-linking was estimated in term of the conversion of azide groups to dibenzyldiazene junctions with liberation of gaseous nitrogen molecules. The micellar structures were studied by dynamic light scattering (DLS) and atomic force microscopy (AFM). Differential scanning calorimetry (DSC) was used to characterize the thermal behavior of freeze-dried micelles. Attachment of PEO block to a rigid core modified considerably the thermal behavior of PEO. We observed a decrease of about 15 °C for the crystallization temperature and 50% for the degree of crystallinity of cross-linked micelles submitted to 45 min UV irradiation compared to pristine copolymer.

Research paper thumbnail of Characterization of Functional Poly(ethylene oxide)s and Their Corresponding Polystyrene Block Copolymers by Liquid Chromatography under Critical Conditions in Organic Solvents

Macromolecules, 2012

Separation of functional poly(ethylene oxide) PEO and PEO block copolymers was investigated using... more Separation of functional poly(ethylene oxide) PEO and PEO block copolymers was investigated using liquid chromatography under critical conditions (LCCC) with a mixture of organic solvents as eluent. The optimum eluent is a mixture of 58.05% chloroform, 6.45% methanol, and 35.50% n-heptane (v/v/v) using a reverse phase (C 8) column. Unlike what was expected, the elution mechanism is governed by the interaction of a polar endgroup with the column. In these conditions, poly(ethylene oxide) (PEO) functionalized with either an acrylate or alkoxyamine moieties were separated. This allows us to investigate the efficiency of the synthesis of poly(ethylene oxide)-b-polystyrene (PEO-b-PS) and polystyrene-b-poly(ethylene oxide) b-polystyrene (PS-b-PEO-b-PS) block copolymers prepared via the combination of 1,2 radical intermolecular addition followed by the nitroxide-mediated polymerization NMP of styrene. Amphiphilic diblock PEO-b-PS and triblock PS-b-PEO-b-PS copolymers were also separated from PEO homopolymers using the same experimental conditions. We showed that the PEO block is then invisible, and the calibration curve obtained using PS homopolymer standards could be used to determine the whole molar mass of the PS block in block copolymers with PS and PEO segments, with a weak influence of the architecture.

Research paper thumbnail of Polyaromatic Structures as Organo-Photoinitiator Catalysts for Efficient Visible Light Induced Dual Radical/Cationic Photopolymerization and Interpenetrated Polymer Networks Synthesis

Macromolecules, 2012

All reagents were purchased from Aldrich or Alfa Aesar and used as received without further purif... more All reagents were purchased from Aldrich or Alfa Aesar and used as received without further purification. Mass spectroscopy was performed by the Spectropole of Aix-Marseille University (Marseille). The HRMS mass spectral analysis was performed with a QStar Elite (Applied Biosystems SCIEX) mass spectrometer. ESI-HRMS measurements were also carried out with a Waters Xevo-QTOF. 1 H and 13 C NMR spectra were determined at room temperature in 5 mm o.d. tubes on a Bruker Avance 400 spectrometer of the Spectropole : 1 H (400 MHz) and 13 C (100 MHz). The 1 H chemical shifts were referenced to the solvent peak: CDCl 3 (7.26 ppm), and the 13 C chemical shifts were referenced to the solvent peak: CDCl 3 (77.0 ppm). The CPMAS and HPDEC spectra were recorded with a spectrometer operating at 10kHz (spinning rate). Purities higher than 90% for the three complexes were determined from the 1 H NMR spectra. Truxene and tribromotruxene were prepared according to a literature procedure. 1 Truxene derivative T_1 was synthesized in one step by a palladium-catalyzed Suzuki-cross coupling reaction between the commercially available pyrene-1-boronic acid and tribromohexahexyltruxene. Suzuki cross coupling occurred efficiently at reflux and under vigorous stirring of a water/toluene/ethanol biphasic mixture using potassium carbonate as base and Pd(PPh 3) 4 as catalyst. Tris(aza)pentacene T_2 was synthesized in one step by condensation of three equivalents of 2,3-diaminophenazine 2 with one equivalent of hexaketocyclohexane (see scheme 1).

Research paper thumbnail of A Step Towards High‐Molecular‐Weight Living/Controlled Polystyrene Using SG1‐Mediated Polymerization

Macromolecular Reaction Engineering, 2010

The synthesis of high‐molecular‐weight living/controlled polystyrene by NMP was studied. The comb... more The synthesis of high‐molecular‐weight living/controlled polystyrene by NMP was studied. The combination of Ac2O and alkoxyamines based on nitroxides TEMPO, TIPNO, and SG1 was tested at 130 °C. With TEMPO and TIPNO, dipole/dipole interactions led to a decrease in nitroxide concentration and an acceleration of the reaction. To minimize thermal auto‐initiation and thus obtain high‐$\overline M _{\rm n}$ PS, the temperature was lowered. At 90 °C, the use of BlocBuilder yielded PS of overlineMrmn\overline M _{\rm n}overlineMrmn = 210 000 g · mol−1 with a living fraction of 60%. Finally, new SG1‐based nitroxides were used to perform the polymerization at 75 °C. Since these nitroxides were too constrained, the decrease in kc caused a loss of control and livingness for high‐$\overline M _{\rm n}$ polymers.magnified image

Research paper thumbnail of Cover Picture: Macromol. Rapid Commun. 3/2006

Macromolecular Rapid Communications, 2006

Cover: The cover picture shows a strategy used to synthesize new functional polyethylenes (PE). A... more Cover: The cover picture shows a strategy used to synthesize new functional polyethylenes (PE). A neodymium based complex catalyzes ethylene chain growth reaction on MgR2 producing Mg(PE)2. Those are excellent candidates to react with disulfides of thiocarbonylated compounds (RC(S)SSC‐(S)R). Further details can be found in the Communication by R. Godoy Lopez, C. Boisson, F. D'Agosto,* R. Spitz, F. Boisson, D. Gigmes, and D. Bertin on page 173.

Research paper thumbnail of New Functional Polyolefins: Towards a Bridge Between Catalytic and RAFT Polymerizations?

Macromolecular Rapid Communications, 2006

Summary: Di‐polyethylenyl magnesium compounds, obtained by a transition metal catalyzed chain gro... more Summary: Di‐polyethylenyl magnesium compounds, obtained by a transition metal catalyzed chain growth reaction on butyloctyl magnesium, are reacted with a range of disulfides of thiocarbonylated compounds (RC(S)SSC(S)R). Xanthate, dithiocarbamate, dithioester, and trithiocarbonate‐functionalized polyethylenes are thus obtained and characterized by 1H NMR and IR spectroscopy, and MALDI TOF mass spectrometry. These macroRAFT agents may serve as building blocks for the synthesis of block copolymers based on polyolefins and polar segments.Thio thiocarbonylate‐terminated polyethylene chains are easily prepared in high yield by a two step reaction and analyzed by MALDI‐TOF mass spectrometry.imageThio thiocarbonylate‐terminated polyethylene chains are easily prepared in high yield by a two step reaction and analyzed by MALDI‐TOF mass spectrometry.

Research paper thumbnail of Random Copolymers with Pendant Cationic Mixed-Ligand Terpyridine-Based Iridium (III) Complexes: Synthesis and Application in Light-Emitting Devices

Macromolecular Chemistry and Physics, 2011

Research paper thumbnail of Poly(D,L-Lactide)-block-Poly(2-Hydroxyethyl Acrylate) Block Copolymers as Potential Biomaterials for Peripheral Nerve Repair: in vitro and in vivo Degradation Studies

Macromolecular Bioscience, 2011

Research paper thumbnail of Organized Formation of 2D Extended Covalent Organic Frameworks at Surfaces

Journal of the American Chemical Society, 2008

The development of nanoscale masking for particle deposition is exceedingly important to push the... more The development of nanoscale masking for particle deposition is exceedingly important to push the future of nanoelectronics beyond the current limits of lithography. We present the first example of ordered hexagonal covalent nanoporous structures deposited in extended arrays of near monolayer coverage across a Ag(111) surface. The networks were formed from the deposition of the reagents from a heated molybdenum crucible between 370 and 460 K under ultrahigh vacuum (UHV) onto a cleaned Ag(111) substrate and imaged using a scanning tunneling microscope (STM). Two surface covalent organic frameworks (SCOFs) are presented; the first is formed from the deposition of 1,4-benzenediboronic acid (BDBA) and its dehydration to form the boroxine-linked SCOF-1, the second is formed from the co-deposition of BDBA and 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP) to form a dioxaborole-linked SCOF-2 network. The networks were found to produce nanoporous structures of 15 A for SCOF-1 and 29 A for SCOF-2, which agreed with theoretical pore sizes determined from DFT calculations. Both SCOFs were found to have exceptional thermal stability, maintaining their structure until approximately 750 K, which was found to be the polymer degradation temperature from thermal gravimetric analysis (TGA).

Research paper thumbnail of Elaboration of densely functionalized polylactide nanoparticles from N -acryloxysuccinimide-based block copolymers

Journal of Polymer Science Part A: Polymer Chemistry, 2011

Poly(N-acryloxysuccinimide) (PNAS) and poly(Nacryloxysuccinimide-coN -vinylpyrrolidone) (P(NAS-co... more Poly(N-acryloxysuccinimide) (PNAS) and poly(Nacryloxysuccinimide-coN -vinylpyrrolidone) (P(NAS-co-NVP)) of adjustable molecular weights and narrow polydispersities were prepared by nitroxide-mediated polymerization (NMP) in N,Ndimethylformamide in the presence of free SG1 (N-tert-butyl-N-1-diethylphosphono-(2,2-dimethylpropyl) nitroxide), with MAMA-SG1 (N-(2-methylpropyl)-N-(1-diethylphosphono-2,2-dimethylpropyl)-O-(2-carboxylprop-2-yl)hydroxylamine) alkoxyamine as initiator. The reactivity ratios of NAS and NVP were determined to be r NAS ¼ 0.12 and r NVP ¼ 0, indicating a strong alternating tendency for the P(NAS-co-NVP) copolymer. NAS/ NVP copolymerization was then performed from a SG1-functionalized poly(D,L-lactide) (PLA-SG1) macro-alkoxyamine as initiator, leading to the corresponding PLA-b-P(NAS-co-NVP) block copolymer, with similar NAS and NVP reactivity ratios as mentioned above. The copolymer was used as a surface modifier for the PLA diafiltration and nanoprecipitation processes to achieve nanoparticles in the range of 450 and 150 nm, respectively. The presence of the functional/hydrophilic P(NAS-co-NVP) block, and particularly the N-succinimidyl (NS) ester moieties at the particle surface, was evidenced by ethanolamine derivatization and zeta potential measurements. V

Research paper thumbnail of Long‐range polar and steric effects in propionate‐SG1‐type alkoxyamines (SG1‐CHMeCOOX): a multiparameter analysis

Journal of Physical Organic Chemistry, 2006

The effects of the substituent X on the homolysis rate constants (kd) of SG1‐propionate type alko... more The effects of the substituent X on the homolysis rate constants (kd) of SG1‐propionate type alkoxyamines (SG1‐CHMeCOOX) are analyzed by a multiparametric equation with υ, the steric constant and σI, the polar inductive/field Hammett constant of X. An influence of long‐range polar and steric effects on kd was observed, that is, decrease in kd with increasing size of the X group and increase in kd with increasing polarity of the X group. Copyright © 2006 John Wiley & Sons, Ltd.

Research paper thumbnail of β-Fragmentation of alkoxyl radicals: Natural bond orbital analysis

International Journal of Quantum Chemistry, 2005

Alkoxyl radicals are often generated in order to perform regioselective hydrogen atom abstraction... more Alkoxyl radicals are often generated in order to perform regioselective hydrogen atom abstraction. However, their ␤-fragmentation generates alkyl radicals that are less efficient to abstract hydrogen atoms. We have performed density functional theory (DFT) calculations [UB3LYP/6-31ϩG(d,p)] followed by a natural bond orbital (NBO) analysis on a series of alkoxyl radicals. The ␤-fragmentation of these radicals is discussed in terms of bond population and hyperconjugative interactions.

Research paper thumbnail of Intramolecular Hydrogen Bonding: The Case of β‐Phosphorylated Nitroxide (= Aminoxyl) Radical

Helvetica Chimica Acta, 2006

Alkoxyamines and persistent nitroxide (= aminoxyl) radicals are important regulators of nitroxide... more Alkoxyamines and persistent nitroxide (= aminoxyl) radicals are important regulators of nitroxide‐mediated radical polymerization. Since polymerization times decrease with the increasing homolysis rate constant of the CON bond homolysis between the polymer chain and the aminooxy moiety, the factors influencing the cleavage rate constant are of considerable interest. It has already been shown that the value of the homolysis rate constant kd is very sensitive to the stabilization of both released radical species. X‐Ray, EPR, and kinetic data showed that the intramolecular H‐bonding radical in the 1‐(diethoxyphosphoryl)‐2,2‐dimethylpropyl 2‐hydroxy‐1,1‐dimethylethyl nitroxide (3a) (homologue of 2‐hydroxy‐1,1‐dimethylethyl 1‐phenyl‐2‐methylpropyl nitroxide (2a)) did not occur with the nitroxide moiety as expected but with the phosphoryl group. However, the polymerization rate of styrene (= ethenylbenzene) was significantly enhanced.