Search

Magnetron sputter deposition of metal targets over liquids allows producing colloidal solutions of small metal nanoparticles (NPs) without any additional reducing or stabilizing reagents. Despite that this synthetic approach is known for almost 15 years, the detailed mechanism of NP formation is still unclear. Detailed investigations must be carried out to better understand the growth mechanism and, ultimately, control the properties of the NPs. Here, the combination of the gold (Au) target and castor oil, a highly available green solvent, was chosen as a model system to investigate how different experimental parameters affect the growth of NPs. The effect of deposition time, applied sputter power, working gas pressure, and type of sputter plasma (direct current magnetron sputtering (DC-MS) vs. high-power impulse magnetron sputtering (HiPIMS)) on properties of Au NPs has been studied by UV-vis spectroscopy and transmission electron microscopy (TEM), and further supported by quantum-chemistry calculations and mass-spectrometry analysis. The mechanism of the Au NP formation includes the production of primary NPs and their subsequent aggregative growth limited by diffusion in the viscous castor oil medium. Final Au NPs have a narrow size distribution and a medium diameter of 2.4–3.2 nm when produced in DC-MS mode. The NP size can be increased up to 5.2 ± 0.8 nm by depositing in HiPIMS mode which, therefore, mimics energy and time-consuming post synthesis annealing.

The attachment of conjugated polymers (CPs), characterized by their optical and electronic properties and excellent processability, to inorganic nanoparticles (NPs), known for their specialized ele...

The research area of nonlinear topologies of conjugated polymers (CPs) became a topic of growing interest due to their unique optoelectronic properties compared to CPs with linear topologies. Nonetheless, the field of the third-order nonlinear optical response (TONO) is still largely unexplored, although, theoretically, nonlinear CPs should give a higher TONO response. Therefore, linear CPs and a trigonal nonlinear CP were synthesized via a combination of a controlled chain-growth polymerization, post-polymerization reactions and a click reaction. Afterward, the TONO response of the CPs was investigated with the highly sensitive third-harmonic scattering technique using solvatochromism experiments. In contrast to what was expected, trigonal nonlinear CPs do not possess a higher TONO response compared to their linear counterparts.

International audience; Pseudomonas aeruginosa is a human pathogen belonging to the top priorities for the discovery of new therapeutic solutions. Its propensity to generate biofilms strongly complicates the treatments required to cure P. aeruginosa infections. Herein we describe the synthesis of a series of novel rotaxanes comprised of a central galactosylated pillar [5]arene, a tetrafucosylated dendron and a tetra-guanidinium subunit. Strategically, we exploited a supramolecular assembly technology to generate complex rotaxanes from relatively simple subcomponents. The final glycorotaxanes displayed high affinity for the two P. aeruginosa lectins LecA and LecB as evaluated by Isothermal Titration Calorimetry. Potent inhibition levels of P. aeruginosa biofilm growth were evidenced showing that the three subunits of the glycorotaxanes work synergistically. Such antibiofilm potency had rarely been reached in the literature. Importantly, none of the final rotaxanes was bactericidal, showing that their antibiofilm activity is lectinmediated but does not depend on bacteria killing, which is a rare feature for antibiofilm agents.

International audience; Research toward bio-based polymers is an expanding field due to environmental concerns. A library of new aliphatic diol-diamide monomers with different chain lengths between the two amido groups was synthesized from sustainable levulinic acid and various linear aliphatic diamines (C 2-C 10). The monomers were prepared by diacylation of the diamines followed by reduction of the ketones to alcohols. These secondary diols were successfully recognized by an enzyme and polymerised in solution through a lipase-catalysed polycondensation. Poly(ester-co-amide)s with number-average molecular weights (M n) in the range of 1300-7200 g mol −1 were obtained, with dispersities between 1.5 and 1.8. An improvement of the M n value was observed upon increasing the monomer chain length. The variation of the aliphatic diol allows modulating the thermal properties of the final polymers. The glass transition temperatures were found to be between −23°C and 0°C. The polymers containing a long aliphatic segment (C 8-C 10) were able to crystallize (melting temperature of 90-97°C). TGA analyses showed that the ester linkages degrade at lower temperatures than the amide bonds. The stability of the latter was found to be higher when the number of methylene units increased from 2 (355°C) to 10 (378°C). This kind of biopolymer could be used as a drug delivery system or for tissue engineering applications. † Electronic supplementary information (ESI) available. See

The epimerization of polylactide is reported in the presence of 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) at 105°C in toluene. The extent of the reaction depends on the amount of TBD introduced and the reaction time. Up to ca. 46% D units can be formed starting from poly(L-lactide) in the presence of 5 mol% TBD. The epimerization rate is slightly higher for D-stereoisomers vs. L-stereoisomers. From the decrease of the number-average molecular weight observed, a concomitant chain scission reaction is observed. A possible mechanism based on a nucleophilic attack of TBD is proposed based on NMR analyses, notably DOSY, MALDI ToF mass spectrometry and IR spectroscopy. The implications of the work in the field of polymer synthesis and chemical recycling of polylactide are discussed. 181;109188

Among the various catalysts that can be used for polycondensation reactions, enzymes have been gaining interest for three decades, offering a green and eco-friendly platform towards the sustainable design of renewable polyesters. However, limitations imposed by their delicate nature, render them less addressed. As a case study, we compare herein bulk and solution polycondensation of 1,6-hexanediol and diethyl adipate catalyzed by an immobilized lipase from Candida antarctica. The influence of various parameters including time, temperature, enzyme loading, and vacuum was assessed in the frame of a two-step polymerization with the help of response surface methodology, a statistical technique that investigates relations between input and output variables. Results in solution (diphenyl ether) and bulk conditions showed that a two-hour reaction time was enough to allow adequate oligomer growth for the first step conducted under atmospheric pressure at 100 &deg, C. The number-average molecular weight (Mn) achieved varied between 5000 and 12,000 g&middot, mol&minus, 1 after a 24 h reaction and up to 18,500 g∙mol&minus, 1 after 48 h. The statistical analysis showed that vacuum was the most influential factor affecting the Mn in diphenyl ether. In sharp contrast, enzyme loading was found to be the most influential parameter in bulk conditions. Recyclability in bulk conditions showed a constant Mn of the polyester over three cycles, while a 17% decrease was noticed in solution. The following work finally introduced a statistical approach that can adequately predict the Mn of poly(hexylene adipate) based on the choice of parameter levels, providing a handy tool in the synthesis of polyesters where the control of molecular weight is of importance.

We report the synthesis, characterization and biological profile of new bis-triazoled cyclopolylactides (c-PLA, c-PLA-FA, c-PLA-Rhod) obtained by an optimized combination of ROP and click chemistry reactions. Cyclo-PLA having a number average molecular weight of 6000 g mol−1 and a polydispersity index of 1.52 was synthetized by click ring-closure of well-defined α,ω-heterodifunctional linear precursors, followed by quaternarization of N3-triazole nodes, and subsequent CuAAC with azido-folate and azido-rhodamine yielding jellyfish-shaped c-PLA-FA and c-PLA-Rhod. Salinomycin (Sal) was loaded into jellyfish-shaped c-PLA-FA and c-PLA-Rhod nanoparticles (NPs) by nanoprecipitation, with a good encapsulation efficiency (79% and 84%, respectively) and loading content (7.1% and 7.6%, respectively). The biological studies focused on their antiproliferative effects on osteosarcoma bulk MG63 and cancer stem cells (CSCs). The cycloPLA-based NPs, with a size ranging between 125 and 385 nm, killed CSCs and MG63, with a higher efficacy on CSCs; they (unloaded or Sal-loaded) evoked on CSCs a cellular response similar to the payload, with a higher effect than the free Sal. Internalization studies indicated a fast cellular uptake (within 2 h) and sarcospheres remained fluorescent till 72 h. To the best of our knowledge, this is the first study reporting anti-CSCs properties of cycloPLA with jellyfish architecture and we believe could contribute to the development of effective strategies for osteosarcoma targeting.

Reactive extrusion and magnesium (II) N-heterocyclic carbene catalyst are successfully employed in continuous polylactide synthesis. The possibility of using six-membered N-heterocyclic carbene adducts to act as efficient catalysts towards the sustainable synthesis of poly(l-lactide) through ring-opening polymerization of l-lactide (LA) is first investigated in bulk batch reactions. Under optimized solvent-free conditions, polylactide (PLA) of moderate to high molecular weights and excellent optical activities are successfully achieved. These promising results are further applied in the continuous production of PLA in an extruder.

A poly(3-hexylthiophene)-block-perfluoropolyether-block-poly(3-hexylthiophene) (P3HT-b-PFPE-b-P3HT) triblock copolymer was synthesized by copper(I)-catalyzed alkyne–azide cycloaddition (CuAAC) in 95% yield. The copolymer was unequivocally characterized by size exclusion chromatography reaching 27 000 g mol−1 and nuclear magnetic resonance (NMR). As expected, diffusion-ordered spectroscopy NMR experiment revealed a lower diffusion coefficient (2.56 × 10-10 m2 s−1) for the P3HT-b-PFPE-b-P3HT triblock copolymer than the ethynyl end-functionalized P3HT (2.83 × 10-10 m2 s−1). Such a triblock copolymer exhibits i) a good thermal stability with no significant weight loss until 320 °C under air, ii) a glass transition of -50 °C due to the soft PFPE segment and iii) a melting peak arising from P3HT at 236 °C. The UV–vis absorption spectrum exhibits a similar absorption profile to that of pure P3HT with a vibronic structure. Analysis of terpolymer thin films by atomic force microscopy imaging and grazing incidence wide-angle X-ray scattering reveals the formation of P3HT crystallites and an “edge-on” orientation of the polymer chains towards the substrate. Preliminary photovoltaic studies on blends of this triblock copolymer combined with a fullerene derivative indicate that the devices using P3HT-b-PFPE-b-P3HT show an almost similar power conversion efficiency to commercial P3HT.

In this work, an atmospheric aerosol assisted pulsed plasma process is reported as an environmentally friendly technique for the preparation of tunable catechol-bearing thin films under solvent and catalyst free conditions. The approach relies on the direct injection of dopamine acrylamide dissolved in 2-hydroxyethylmethacrylate as comonomer into the plasma zone. By adjusting the pulsing of the electrical discharge, the reactive plasma process can be alternatively switch ON (tON) and OFF (tOFF) during different periods of time, thus allowing a facile and fine tuning of the catechol density, morphology and deposition rate of the coating. An optimal tON/tOFF ratio is established, that permits maximizing the catechol content in the deposited film. Finally, a diagram, based on the average energy input into the process, is proposed allowing for easy custom synthesis of layers with specific chemical and physical properties, thus highlighting the utility of the developed dry plasma route.

End-functionalized poly(3-hexylthiophene) (P3HT) and poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl methacrylate) (PTMA) were synthesized using controlled polymerization techniques and linked together to lead to a diblock copolymer structure via click cycloaddition. These diblock copolymers were further blended with carbon nanotubes (CNTs) to be used as cathodes in organic radical batteries. The performances of these batteries were studied during charge/discharge cycling at constant and variable current densities (C rate). In order to shed light on the importance of the diblock copolymer architecture, the results were compared to the capacities measured on electrodes made of blends of P3HT and PTMA homopolymers. Theoretical simulations were finally used to corroborate the good electrochemical properties of the synthesized diblock copolymers.

© 2018 American Chemical Society. The new conjugated poly(4,4-bis(2-ethylhexyl)cyclopentadithiophene-alt-p-phenylene) (PCPDTPP) has been synthesized in a controlled way via catalyst transfer condensative polymerization (CTCP) of the corresponding biaryl monomer. Therefore, a series of Ni catalysts as well as (new) Pd-PEPPSI catalysts were employed in different Kumada CTCPs (KCTCPs) and Negishi CTCPs (NCTCPs). A series of tests confirmed the absence of undesired transfer and termination reactions and, hence, the controlled character of the chain-growth polymerization with Ni(dppe)Cl2 as catalyst. This resulted in polymers with low dispersities (D = 1.2), Mn of 33 kDa, and relatively good end-group control. Furthermore, formation of PCPDTPP-b-poly(3-octylthiophene) (P3OT) block copolymers was possible. Via optical analysis and DSC measurements, we demonstrated that the conjugated alternating PCPDTPP copolymer is an amorphous, strongly fluorescent polymer with a fluorescence quantum yield (ψf) of 58% in chloroform. ispartof: MACROMOLECULES vol:51 issue:21 pages:9043-9051 status: published

Biomolecular machines perform types of complex molecular-level tasks that artificial molecular machines can aspire to. The ribosome, for example, translates information from the polymer track it traverses (messenger RNA) to the new polymer it constructs (a polypeptide) 1 . The sequence and number of codons read determines the sequence and number of building blocks incorporated into the biomachine-synthesized polymer. However, neither control of sequence2,3 nor the transfer of length information from one polymer to another (which to date has only been accomplished in man-made systems through template synthesis) 4 is easily achieved in the synthesis of artificial macromolecules. Rotaxane-based molecular machines5–7 have been developed that successively add amino acids8–10 (including β-amino acids 10 ) to a growing peptide chain by the action of a macrocycle moving along a mono-dispersed oligomeric track derivatized with amino-acid phenol esters. The threaded macrocycle picks up groups that block its path and links them through successive native chemical ligation reactions 11 to form a peptide sequence corresponding to the order of the building blocks on the track. Here, we show that as an alternative to translating sequence information, a rotaxane molecular machine can transfer the narrow polydispersity of a leucine-ester-derivatized polystyrene chain synthesized by atom transfer radical polymerization 12 to a molecular-machine-made homo-leucine oligomer. The resulting narrow-molecular-weight oligomer folds to an α-helical secondary structure 13 that acts as an asymmetric catalyst for the Julia–Colonna epoxidation14,15 of chalcones. The ring of a rotaxane molecule traverses a polymer track picking up leucine amino acids and synthesizing a homo-leucine oligomer, which in turn folds into an alpha helix and catalyses a chemical reaction.

Ring closure click chemistry methods have been used to produce cyclic c-PLLA and c-PDLA of a number-average molecular weight close to 10 kg/mol. The effects of stereochemistry of the polymer chains and their topology on their structure, nucleation, and crystallization were studied in detail employing wide-angle X-ray scattering (WAXS), small-angle X-ray scattering (SAXS), polarized light optical microscopy (PLOM), and standard and advanced differential scanning calorimetry (DSC). The crystal structures of linear and cyclic PLAs are identical to each other, and no differences in superstructural morphology could be detected. Cyclic PLA chains are able to nucleate much faster and to produce a higher number of nuclei in comparison to linear analogues, either upon cooling from the melt or upon heating from the glassy state. In the samples prepared in this work, a small fraction of linear or higher molecular weight cycles were detected (according to SEC analyses). The presence of such “impurities” retards spherulitic growth rates of c-PLAs, making them nearly the same as those of l-PLAs. On the other hand, the overall crystallization rate determined by DSC was much larger for c-PLAs, as a consequence of the enhanced nucleation that occurs in cyclic chains. The equilibrium melting temperatures of cyclic chains were determined and found to be 5 °C higher in comparison with values for l-PLAs. This result is a consequence of the lower entropy of cyclic chains in the melt. Self-nucleation studies demonstrated that c-PLAs have a shorter crystalline memory than linear analogues, as a result of their lower entanglement density. Successive self-nucleation and annealing (SSA) experiments reveal the remarkable ability of cyclic molecules to thicken, even to the point of crystallization with extended collapsed ring conformations. In general terms, stereochemistry had less influence on the results obtained in comparison with the dominating effect of chain topology., The UPV/EHU team acknowledges funding from the following projects: “UPV/EHU Infrastructure: INF 14/38”; “Mineco/FEDER: SINF 130I001726XV1/Ref: UNPV13-4E-1726” and “Mineco MAT2014-53437−C2-P”, ’Ministerio de Economia y Competitividad (MINECO), code: MAT2015-63704-P (MINECO/FEDER, UE) and by the Eusko Jaurlaritza (Basque Government), code: IT-654-13. O.C. acknowledges financial support from the European Commission and Region Wallonne FEDER program (Materia Nova) and OPTI2 MAT program of excellence, by the Interuniversity Attraction Pole Program (P7/ 05) initiated by the Belgian Science Policy office and by the FNRS-FRFC. O.C. is a Research Associate of the F.R.S.-FNRS. The Organic Synthesis and Mass Spectrometry Laboratory thanks F.R.S.-FNRS for the financial support for the acquisition of the Waters QToF Premier and Synapt-G2Si mass spectrometers and for continuing support. Finally, all authors acknowledge Research and Innovation Staff Exchange (RISE) H2020-MSCA-RISE-2017-778092, project BIODEST, for promoting cooperation between the Mons team and the UPV/EHU team.

Ruthenium-based complexes are widely used as photocatalysts, as photosensitizers, or as building blocks for supramolecular assemblies. In the field of solar energy conversion, building light harvesting antenna is of prime interest. Nevertheless, collecting light is mandatory but not sufficient; once collected and transferred, the exciton has to be long-lived enough to be transferred to a catalytic site. If Ru(II) terpyridine complexes are prime building blocks for structural reasons, the short lifetime of their excited state prevents their use as a harvesting center in light antennae. In this paper, we present new polynuclear assemblies, based on Ru(II)-terpyridine units where delocalization of the excited state is combined with an antenna effect. As a consequence, complexes C1–C3 display long-lived excited states compared to [Ru(tpy)2]2+, making them promising efficient antenna building blocks to be connected to a final acceptor or a catalytic center.

Photoactive ruthenium-based complexes are actively studied for their biological applications as potential theragnostic agents against cancer. One major issue of these inorganic complexes is to penetrate inside cells in order to fulfil their function, either sensing the internal cell environment or exert a photocytotoxic activity. The use of lipophilic ligands allows the corresponding ruthenium complexes to passively diffuse inside cells but limits their structural and photophysical properties. Moreover, this strategy does not provide any cell selectivity. This limitation is also faced by complexes anchored on cell-penetrating peptides. In order to provide a selective cell targeting, we developed a multivalent system composed of a photoreactive ruthenium(II) complex tethered to a calix[4]arene platform bearing multiple RGD-containing cyclopentapeptides. Extensive photophysical and photochemical characterizations of this Ru(II)-calixarene conjugate as well as the study of its photoreactivity in the presence of guanosine monophosphate have been achieved. The results show that the ruthenium complex should be able to perform efficiently its photoinduced cytotoxic activity, once incorporated into targeted cancer cells thanks to the multivalent platform., info:eu-repo/semantics/published

International audience; Organic semiconductors are increasingly being used in organic-based opto-electronic devices. Since regioselective synthetic approaches are not always controlled, promising compounds are sometimes prepared following non-regioselective routes. Ion mobility mass spectrometry is here introduced as a direct method to distinguish isomers in mixtures, instead of undertaking time-consuming analytical chromatography procedures. © 2018 The Royal Society of Chemistry.

International audience; One of the main issues when using traveling wave ion mobility spectrometry (TWIMS) for the determination of collisional cross-section (CCS) concerns the need for a robust calibration procedure built from referent ions of known CCS. Here, we implement synthetic polymer ions as CCS calibrants in positive ion mode. Based on their intrinsic polydispersities, polymers offer in a single sample the opportunity to generate, upon electrospray ionization, numerous ions covering a broad mass range and a large CCS window for different charge states at a time. In addition, the key advantage of polymer ions as CCS calibrants lies in the robustness of their gas-phase structure with respect to the instrumental conditions, making them less prone to collisional-induced unfolding (CIU) than protein ions. In this paper, we present a CCS calibration procedure using sodium cationized polylactide and polyethylene glycol, PLA and PEG, as calibrants with reference CCS determined on a home-made drift tube. Our calibration procedure is further validated by testing the polymer calibration to determine CCS of numerous different ions for which CCS are reported in the literature.

The organocatalytic coupling of CO2 with oxetanes is investigated under solvent-free conditions. The influence of the main reaction parameters (type of organocatalytic system, pressure, and temperature) on the yield, the product formed, and the selectivity of the reaction are discussed. An onium salt combined with a fluorinated alcohol promotes the efficient and selective organocatalytic synthesis of α,ω-hydroxyl oligocarbonates by coupling CO2 with oxetanes at 130 °C and at a CO2 pressure as low as 2 MPa. NMR characterizations were correlated with matrix-assisted laser desorption/ionization with time-of-flight mass spectrometer (MALDI-TOF) analyses for elucidating the structure of the oligomers. Online FTIR studies under pressure, NMR titrations, and DFT calculations allowed an in-depth understanding of the reaction mechanism. Finally, CO2-based poly(carbonate-co-urethane)s were synthesized by step-growth polymerization of hydroxyl telechelic oligocarbonates with 4,4′-methylene diphenyl diisocyanate (MDI). The organocatalytic system described herein constitutes an innovative sustainable route to the selective preparation of hydroxyl telechelic carbonates of high interest for many applications, notably for the polyurethane business (especially for coatings or foams).

International audience; The preparation and characterization of three series of novel ruthenium(ii) complexes are reported, each series differing by the nature of the ancillary ligands (2,2'-bipyridine - bpy, 1,10-phenanthroline - phen or 1,4,5,8-tetraazaphenanthrene - TAP). The third ligand was either the heptacyclic heterocycle dipyrido[3,2-a:2',3'-c]quinolino[3,2-h]phenazine (dpqp) substituted at position 12 by an hydroxyl (oxo), 2,2-dimethoxyethylamine (DMEA) or halogeno (Cl or Br) substituent, or the octacyclic dipyrido[3,2-a:2',3'-c]pyrido[2,3,4-de]quinolino[3,2-h]phenazine (dppqp), prepared by a multi-step "chemistry on the complex" strategy from [RuL2(oxo-dpqp)](PF6)2. The three steps, halogenation, substitution by a dimethoxyethylamino group and cyclization in trifluoroacetic acid, were performed in reasonable to high yields depending on the nature of the ancillary ligands. Isolation and purification processes were facilitated by the ability to switch the solubility of the complex from aqueous to organic solvents, depending on the counter-ion. All new complexes were fully characterized; in particular their absorption properties were compared by UV-vis spectroscopy. Finally, π-stacking properties induced by these extended ligands were studied by 1H NMR studies and quantum chemical calculations.

© 2016 Wiley Periodicals, Inc. This article deals with the Kumada Catalyst Transfer Polycondensation (KCTP) of 4,7-dioctylbenzo[2,1-b:3,4-b']dithiophene (BDP-Oct) using Ni(II) catalyst or In/cat combination. A combination of MALDI MS, GPC, and 31P NMR spectroscopy is used to reveal the failure of the KCTP of this particular monomer. Intermolecular transfer reactions to monomer appeared to prevent the formation of polymer. This result is remarkable, since isomeric benzo[1,2-b:4,5-b']dithiophene polymerizes in a controlled way. The presence of a "non-aromatic double bond" in annulated monomers is discussed. ispartof: Journal of Polymer Science A, Polymer Chemistry vol:54 issue:12 pages:1706-1712 status: published

Saponins are secondary metabolites that are abundant and diversified in echinoderms. Mass spectrometry is increasingly used not only to identify saponin congeners within animal extracts but also to decipher the structure/biological activity relationships of these molecules by determining their inter-organ and inter-individual variability. The usual method requires extensive purification procedures to prepare saponin extracts compatible with mass spectrometry analysis. Here, we selected the sea star Asterias rubens as a model animal to prove that direct analysis of saponins can be performed on tissue sections. We also demonstrated that carboxymethyl cellulose can be used as an embedding medium to facilitate the cryosectioning procedure. Matrix-assisted laser desorption/ionization (MALDI) imaging was also revealed to afford interesting data on the distribution of saponin molecules within the tissues. We indeed highlight that saponins are located not only inside the body wall of the animals but also within the mucus layer that probably protects the animal against external aggressions. Graphical Abstract Saponins are the most abundant secondary metabolites in sea stars. They should therefore participate in important biological activities. Here, MALDI imaging is presented as a powerful method to determine the spatial distribution of saponins within the animal tissues. The inhomogeneity of the intra-organ saponin distribution is highlighted, paving the way for future elegant structure/activity relationship investigations.

The covalent photoadduct (PA) between [Ru(TAP)3](2+) (TAP = 1,4,5,8-tetraazaphenanthrene) and guanosine monophosphate (GMP) opened the way to interesting photobiological applications. In this context, the PA's capability upon illumination to give rise to the addition of a second guanine base is especially interesting. The origins of these intriguing properties are for the first time thoroughly investigated by an experimental and theoretical approach. The PA's spectroscopic and redox data combined with TDDFT results corroborated with resonance Raman data show that the properties of this PA (pKa around 7) depend on the solution pH. Theoretical results indicate that the acid form PA.H(+) when excited should relax to MLCT (metal-to-ligand charge transfer) excited states, in contrast to the basic form PA whose excited state should have LLCT/ILCT (ligand-to-ligand charge transfer/intra ligand charge transfer) characteristics. Ultrafast excitation of PA.H(+) at pH 5.9 produces continuous dynamic processes in a few hundred picoseconds involving coupled proton-electron transfers responsible for luminescence quenching. Long-lived species of a few microseconds capable of reacting with GMP are produced at that pH, in agreement with the formation of covalent addition of a second GMP to PA, as shown by mass spectrometry results. In contrast, at pH 8 (mainly nonprotonated PA), other ultrafast transient species are detected and no GMP biadduct is formed in the presence of GMP. This pH dependence of photoreaction can be rationalized with the different nature of the excited states, thus at pH 8, unreactive LLCT/ILCT states and at pH 5.9 reactive MLCT states. ispartof: Journal of Physical Chemistry B vol:119 issue:12 pages:4488-500 ispartof: location:United States status: published

© 2014 American Chemical Society. The synthesis of a block copoly(3-alkylthiophene) consisting of two different P3AT blocks equipped with an H-donor and -acceptor functionality is presented. The P3ATs were synthesized using a functionalized Ni-initiator. By a series of postpolymerization reactions, including click chemistry, an H-donor and -acceptor entity was attached to the end of the polymer chains. Evidence for a quantitative functionalization of the polymers was provided by 1H NMR and MALDI-ToF analyses. Chiral side chains were implemented on one of both blocks, allowing the study of the influence of the H-bond formation on the chiral self-assembly using UV-vis and circular dichroism spectroscopy. ispartof: Macromolecules vol:48 issue:1 pages:90-98 status: published

© 2015 American Chemical Society. Different protected thiol-functionalized initiators were prepared and used to polymerize end-functionalized poly(3-hexylthiophene)s in which the spacer between the thiol and the P3HT chain is varied. The protected thiol P3HTs were in situ deprotected and anchored onto Au nanoparticles (NPs) to form P3HT/Au hybrids. The influence of the length of the linker between the P3HT and the Au NP surface on the fluorescence quenching was investigated. The strongest quenching was observed for the shortest linkers. Also, a protected thiol poly(3-octylselenophene) (P3OS) was polymerized and anchored together and separately with P3HT to a Au NP. The effect of the presence of P3OS on the quenching was investigated, and an additional quenching was observed when P3OS is anchored on the same NP as P3HT. For all polymers, 1H NMR and MALDI-ToF analysis confirmed the successful functionalization and strong control over the polymerization. ispartof: Macromolecules vol:48 issue:24 pages:8752-8759 status: published

International audience; In this communication we report the first homopolymerization of a variety of methacrylates by an NMP process at moderate temperature (40-50 degrees C), using an easily accessible and inexpensive nitroxide precursor. The combination of a low temperature azo-initiator with a hindered nitroso-compound produces a mixture of hindered nitroxides in the polymerization medium that act as efficient polymerization control agents. Results of Electron Spin Resonance (ESR) spectroscopy experiments combined with mass spectrometric studies support the proposed in situ NMP mechanism. The hindered structure of the nitroxides formed in situ is believed to be responsible for the efficiency of the process by allowing it to proceed at low temperature, therefore limiting the side reactions generally observed in NMP of methacrylates.

International audience; Noncovalent interactions between several protonated amines and an original ditopic receptor, nor-seco-cucurbit[10]uril, are investigated by combining mass spectrometry-based methods and computational chemistry. Electrospray ionization is used to transfer the intact supramolecular assemblies from their acidic solution to the gas phase, provided fine-tuning of the source parameters is achieved. Ternary complexes, associating two guest molecules and one host cavity, are observed systematically in the mass spectrometry analyses and the quasi-exclusive occurrence of these 2:1associations reveals the allosteric nature of the complexation reaction. It is demonstrated that the binary 1:1complex ions that are detected arise from collision-induced dissociation processes undergone by the ternary complex ions inside the ion source. Based on ion mobility experiments supported by theoretical calculations, the inclusion nature of the gas-phase ternary complexes is clearly evidenced independent of the size of the probed guest molecule and the charge state of the complex ions. The allosteric nature of the complexation reactions is dictated by size criteria. This is demonstrated on the basis of mass spectrometry experiments by analyzing solutions containing ligands of different sizes in competition for inclusion within the guest cavity. Computational chemistry is also used to characterize the three-dimensional structures of the complexes.

International audience; Regioregular head-to-tail -bromo--carboxystyryl poly(3-hexylthiophene) (P3HT-COOH) has been prepared by a Wittig reaction of -bromo--formyl poly(3-hexylthiophene) (P3HT-CHO) with [(4-carboxyphenyl)methyl]triphenylphosphonium bromide. This carboxylic end-group functionalized polymer was used to functionalize TiO2 nanoparticles in view of improving the miscibility between poly(3-hexylthiophene) and the nanoparticles, for future photovoltaic applications. The anchoring of the polymer on the surface of the TiO2 nanoparticles was demonstrated by sedimentation tests in THF, and by thermogravimetric analysis (TGA), Transmission Electron Microscopy (TEM), 1H MAS solid-state NMR, UV-Vis and X-ray photoelectron spectroscopies. Films were produced by solvent casting and the dispersion of the TiO2 nanoparticles was evaluated by Atomic Force Microscopy (AFM). Fluorescence quenching studies in CHCl3 were performed on these hybrids materials.

RuII-TAP complexes have been shown to be very attractive compounds in the frame of developments of new anticancer drugs targeting the genetic material. This increasing interest originates from observations of covalent bond formations, triggered by photo-induced electron transfer (PET) between RuII-TAP complexes and guanine bases of DNA. This photoreaction has recently been extended to the tryptophan (Trp) amino acid for future applications involving peptides. Thus, a double photo-addition of Trp residues of peptides on RuII complexes is demonstrated by mass spectrometry with some structural issues. Such bi-adduct formations offer the possibility of photocrosslinking two Trp-containing biomolecules, which is investigated in this study. Thus, photocrosslinking between two complementary oligonucleotides (ODNs) derivatized by Trp-containing tripeptides is demonstrated by polyacrylamide gel electrophoresis (PAGE) in the presence of RuII-TAP complexes. Both PAGE and MS indicate that such photocrosslinkings arise from two reaction pathways: either via the double addition of Trp residues on the Ru complex or from dimerization of Trp radicals. The competition between these two pathways depends on the experimental conditions. Heterobridgings between guanine bases and tryptophan residues mediated by RuII-TAP complexes is also examined, opening the way to ODN-peptide photocrosslinkings. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim., SCOPUS: ar.j, FLWIN, info:eu-repo/semantics/published

Polythiophenes with alcohol, tosylate, azide, ethynylene, carboxylic acid, and amine end groups were prepared by a combination of functionalized nickel initiators and postpolymerization reactions. The azide and ethynylene polymers were subsequently used in a click reaction to produce a conjugated block copolymer. Finally, a conjugated triblock-copolymer was synthesized by means of a chain growth polymerization initiated by a binuclear nickel initiator. ispartof: Macromolecules vol:44 issue:15 pages:6017-6025 status: published

International audience; Cobalt‐mediated radical coupling (CMRC) is a straightforward approach to the synthesis of symmetrical macromolecules that relies on the addition of 1,3‐diene compounds onto polymer precursors preformed by cobalt‐mediated radical polymerization (CMRP). Mechanistic features that make this process so efficient for radical polymer coupling are reported here. The mechanism was established on the basis of NMR spectroscopy and MALDI‐MS analyses of the coupling product and corroborated by DFT calculations. A key feature of CMRC is the preferential insertion of two diene units in the middle of the chain of the coupling product mainly according to a trans‐1,4‐addition pathway. The large tolerance of CMRC towards the diene structure is demonstrated and the impact of this new coupling method on macromolecular engineering is discussed, especially for midchain functionalization of polymers. It is worth noting that the interest in CMRC goes beyond the field of polymer chemistry, since it constitutes a novel carbon–carbon bond formation method that could be applied to small organic molecules.

The low-kinetic energy collision-induced dissociation (CID) behavior of different sodium-cationized polylactide (PLA) oligomers was thoroughly investigated to shed some light on the analytical potentialities of CID experiments in the context of polymer characterization. Indeed, investigation of several end-groups modified PLA reveals that, in addition to the expected end-group specific dissociations, collisionally-excited PLA.Na(+) suffer from a backbone cleavage. The so-obtained sodium-bound dimer cations consecutively undergo the loss of a monomeric residue that corresponds to neutral acrylic acid. The experimental observations, performed on a hybrid Q-ToF instrument, were totally corroborated by a theoretical study involving DFT calculations, molecular mechanics, and molecular dynamics calculations.

International audience; The self-assembly of functional polythiophenes was studied by a bottom-up approach “from molecule to polymer”. The synthesis and the X-ray structure of 2,5-dibromo-3-styryl and 3-2',3',4',5',6'-pentafluorostyryl-thiophenes revealed a supramolecular arrangement controlled by π-π interactions between the aromatic rings. A [2+2] photocyclization reaction in the solid state of (E)-1-2',5'-dibromo-3'-thienyl-2-pentafluorophenylethene triggers the formation of a rare cycloadduct composed by thiophene rings. The X-ray analysis confirmed its rctt stereochemistry. The synthesis of P3HT-b-P3ST and P3HT-b-P3STF block oligomers was achieved by a GRIM method in good yields. An indirect proof of well-defined nanostructured organization was provided by the partial photocyclization of pendant styryl moieties under UV-irradiation.

International audience; Cobalt-mediated radical coupling (CMRC) is successfully applied to poly(vinyl acetate) (PVAc) and poly(N-vinylpyrrolidone) (PNVP) precursors for the first time. The coupling process is based on addition of isoprene onto polymer chains preformed by controlled radical polymerization with cobalt complexes (CMRP). The extents of coupling were high (>90%) to moderate (75−80%) for PVAc and PNVP precursors, respectively. Effects of the length of the polymer precursors and conditions used in the polymerization step on the coupling efficiency are discussed. Mass spectrometry (MS) and nuclear magnetic resonance (NMR) analyses conducted on the coupling products demonstrate the preferential insertion of two isoprene units in the final polymers. The CMRC mechanistic proposal, supported by DFT calculations, is based on this microstructure feature. Finally, illustration of the macromolecular engineering potential of this technique is given by the preparation of symmetrical PVAc-b-PNVP-b-PVAc triblock copolymers starting from the corresponding PVAc-b-PNVP-[Co] diblock copolymer.

This manuscript investigates the use of arylnickel complexes for the synthesis of functionalized conjugated polymers is. The scope of the catalyst-transfer polycondensation of poly(3-alkylthiophene) using nickel was expanded by functionalizing and isolating the nickel initiator. o-Methyl substituted arylnickel complexes were isolated and used to initiate the polymerization of various substituted poly(thiophene)s and poly(p-phenylene). Finally, the living nature of the polymerization of poly(3-alkylthiophene) was exploited to prepare a polymer with two different end-groups – one arising from the Ni-initiator and one from the end-capper. ispartof: Macromolecules vol:42 issue:20 pages:7638-7641 status: published