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Metatla N.,Université de Sherbrooke | Palato S.,Université de Sherbrooke | Commarieu B.,Quebec Center for Functional Materials | Claverie J.P.,Quebec Center for Functional Materials | Soldera A.,Université de Sherbrooke
Soft Matter | Year: 2012

Polymer nanocrystals have attracted considerable attention because of their potential applications in future technology and their fascinating properties which differ from those of corresponding bulk materials. The essential influence of the nanointerface in nanocrystals is apparent in the linear dependence of the melting temperature with the inverse sheet thickness, i.e. the Gibbs-Thomson behaviour. Yet, few experimental and theoretical works have been attempted to highlight the influence of nanointerfaces on the thermal properties of nanocrystals. In this work, simulations were used to evaluate the melting temperature of crystalline polymer nanosheets. Ensuing results were compared favourably to experimental melting temperatures stemming from alkane chains and functional polyolefins, thus validating our simulation approach. Both experimental and simulated results followed Gibbs-Thomson behaviour and a procedure was devised to extract the heat of melting as well as the surface energy from these results. Thus, surface energy of various nanocrystals was found to be widely different for various experimental systems, demonstrating the significance of the environment on thermal properties of nanocrystals.

Daigle J.-C.,Quebec Center for Functional Materials | Piche L.,Quebec Center for Functional Materials | Claverie J.P.,Quebec Center for Functional Materials
Macromolecules | Year: 2011

Linear copolymers of ethylene and acrylic acid (AA) were found to exhibit higher crystallinity and melting points than their branched counterparts. The copolymers were prepared by catalytic copolymerization of ethylene with tert-butyl acrylate followed by deprotection of the ester. The AA-containing polymers proved to be difficult to purify and to analyze due to the formation of intramolecular H-bonds which prevent the polymer from being redissolved. Incorporation of MA proved to be more difficult, as large amounts are necessary for low molar insertions, resulting in the formation of low-molecular-weight polymers. The solvent effect on comonomer insertion is similar to the solvent effect on molecular weight distribution observed with related Pd aryl sulfonates. These copolymers are essentially linear, with only Me branches observed in low amounts.

Zhang J.,Quebec Center for Functional Materials | Abbasi F.,Quebec Center for Functional Materials | Claverie J.,Quebec Center for Functional Materials
Chemistry - A European Journal | Year: 2015

Access to high-quality, easily dispersible carbon quantum dots (CQDs) is essential in order to fully exploit their desirable properties. Copolymers based on N-acryloyl-D-glucosamine and acrylic acid prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization are self-assembled into micelle-like nanoreactors. After a facile graphitization process (170C, atmospheric pressure), each micellar template is transformed into a CQD through a 1:1 copy process. These high-quality CQDs (quantum yield=22%) with tunable sizes (2-5 nm) are decorated by carboxylic acid moieties and can be spontaneously redispersed in water and polar organic solvents. This preparation method renders the mass production of multifunctional CQDs possible. To demonstrate the versatility of this approach, CQDs hybridized TiO2 nanoparticles with enhanced photocatalytic activity under visible-light have been prepared. Quantum dots of solace: Using an efficient process amenable to large scale production, carbon quantum dots (CQDs) were synthesized by carbonizing polymeric self-assembled nanostructures. The CQDs are redispersable, and their size/optical property can be tailored by simply varying the polymer amount or structure. The CQDs hybridized TiO2 nanoparticles demonstrate significantly enhanced photocatalytic activity under visible-light. © 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Zhong W.,Quebec Center for Functional Materials | Claverie J.P.,Quebec Center for Functional Materials
Carbon | Year: 2013

Adsorption isotherms of four different surfactants, sodium dodecyl sulfate (SDS), sodium dodecyl benzyl sulfonate, benzethonium chloride and Triton X-100 were measured on multi-wall carbon nanotubes (MWCNT) in water. With the surfactant SDS, the isotherms were also measured on single-wall carbon nanotubes (SWCNT) as well as on MWCNT under various ionic strength and temperature conditions. The nature of the polar head had only little influence on adsorption which was mainly driven by hydrophobic interactions. However, the outcome of the dispersion experiment was dependent on the purity of the carbon nanotubes. Using these results, it was possible to prepare concentrated colloidaly stable dispersions of MWCNTs in water (c = 32 g/L). Conducting MWCNT/polymer composite films could then readily be prepared by simple formulation of the MWCNTs with a polymeric dispersion. © 2012 Published by Elsevier Ltd.

Das P.,Quebec Center for Functional Materials | Claverie J.P.,Quebec Center for Functional Materials
Journal of Polymer Science, Part A: Polymer Chemistry | Year: 2012

We report here a simple and direct route for the preparation of lead sulfide (PbS) quantum dots (QDs) embedded into polymeric nanospheres by emulsion polymerization. In this process, QDs are first dispersed in an aqueous solution containing a statistical oligomer constituted of five butyl acrylate and ten acrylic acid units prepared by reversible addition fragmentation chain transfer (RAFT) polymerization using a trithiocarbonate as RAFT agent. Then, the dispersion of PbS QDs is engaged into an emulsion polymerization process to form core-shell nanoparticles. Transmission electron microscopy reveals the presence of single-core core-shell particles at low concentration of PbS QD, whereas multiple-core core-shell particles containing either well separated or aggregated PbS QDs are formed at high concentration of PbS QDs. © 2012 Wiley Periodicals, Inc.

Commarieu B.,Quebec Center for Functional Materials | Claverie J.P.,Quebec Center for Functional Materials
Chemical Science | Year: 2015

The catalytic 1,2-insertion polymerization of polar norbornenes (NBEs) leads to the formation of functional rigid macromolecules with exceptional thermal, optical and mechanical properties. However, this remarkable reaction is plagued by the low reactivity of the polar monomers, and most notably of those bearing a functional group in endo position. We have examined the polymerization mechanism of NBEs bearing one or two CO2Me groups either in exo or endo position catalyzed by the so-called naked allyl Pd+ SbF6 - catalyst (1). Although endo dimethyl ester of 5-norbornene-2,3-dicarboxylic acid (NBE(CO2Me)2) is polymerized by 1, two endo units are never inserted consecutively along the polymer chain. Indeed, 1 is a tandem catalyst which not only catalyzes the insertion of the monomer but also the isomerization of endo and exo isomers. Thus, the polymerization of endo monomers proceeds via a novel mechanism, coined rectification-insertion mechanism, whereby half of the endo monomers are rectified into exo ones prior insertion, leading to the formation of an alternating endo-exo copolymer using an endo only feedstock. With this mechanism, the lack of reactivity of endo norbornenes is bypassed, and the polymerization of predominantly endo polar NBEs bearing a variety of functionalities such as esters, imides, acids, aldehydes, alcohols, anhydrides, or alkyl bromides proceeds with catalyst loadings as low as 0.002 mol%. This journal is © The Royal Society of Chemistry.

Daigle J.-C.,Quebec Center for Functional Materials | Piche L.,Quebec Center for Functional Materials | Arnold A.,Quebec Center for Functional Materials | Claverie J.P.,Quebec Center for Functional Materials
ACS Macro Letters | Year: 2012

When palladium phosphine sulfonate catalysts were used, ethylene and allyl acrylate were copolymerized. The copolymer structure was analyzed by Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR) and was found to contain both δ-valerolactone and γ- butyrolactones inserted within the chain. These cyclic structures were determined to be the outcome of 1,2 allyl insertions and 2,1 acrylate insertions except when the acrylate was cyclopolymerized: in this case, regiochemistry of the insertion was 1,2. This first example of cyclopolymerization with Pd phosphine sulfonate catalysts outlines the extraordinary versatility of this family of compounds and paves the way to new polyolefins containing complex repeat units built in. © 2012 American Chemical Society.

Zhong W.,Quebec Center for Functional Materials | Zeuna J.N.,Quebec Center for Functional Materials | Claverie J.P.,Quebec Center for Functional Materials
Journal of Polymer Science, Part A: Polymer Chemistry | Year: 2012

Using a RAFT polymerization process, uniform polymer coats are physically adsorbed onto the surface of a SWNT and MWNT. Copyright © 2012 Wiley Periodicals, Inc.

Daigle J.-C.,Quebec Center for Functional Materials | Dube-Savoie V.,INRS - Institute National de la Recherche Scientifique | Tavares A.C.,INRS - Institute National de la Recherche Scientifique | Claverie J.P.,Quebec Center for Functional Materials
Journal of Polymer Science, Part A: Polymer Chemistry | Year: 2013

Terpolymers of ethylene, norbornene, and 5-exo norbornene methyl alcohol are prepared using Pd phosphine sulfonates as catalysts. The pendant hydroxyl groups are then transformed into thioacetate groups. Films cast from the resulting polymers are then oxidized by hydrogen peroxide. This green oxidation method is found to quantitatively transform thioacetate groups into sulfonic acids, leading to the formation of sulfonated hydrocarbon ionomers. These ionomers are thermally stable, exhibit increasing conductivity up to 110 °C, and have a low water uptake, indicating that these materials are potentially interesting candidates for the preparation of fuel cell membranes. © 2013 Wiley Periodicals, Inc.

PubMed | Quebec Center for Functional Materials and Shandong University
Type: Journal Article | Journal: ACS applied materials & interfaces | Year: 2016

Nanocomposites composed of TiO2 and carbon materials (C) are widely popular photocatalysts because they combine the advantages of TiO2 (good UV photocatalytic activity, low cost, and stability) to the enhanced charge carrier separation and lower charge transfer resistance brought by carbon. However, the presence of carbon can also be detrimental to the photocatalytic performance as it can block the passage of light and prevent the reactant from accessing the TiO2 surface. Here using a novel interfacial in situ polymer encapsulation-graphitization method, where a glucose-containing polymer was grown directly on the surface of the TiO2, we have prepared uniform TiO2@C core-shell structures. The thickness of the carbon shell can be precisely and easily tuned between 0.5 and 8 nm by simply programming the polymer growth on TiO2. The resulting core@shell TiO2@C nanostructures are not black and they possess the highest activity for the photodegradation of organic compounds when the carbon shell thickness is 1-2 nm, corresponding to 3-5 graphene layers. Photoluminescence and photocurrent generation tests further confirm the crucial contribution of the carbon shell on charge carrier separation and transport. This in situ polymeric encapsulation approach allows for the careful tuning of the thickness of graphite-like carbon, and it potentially constitutes a general and efficient route to prepare other oxide@C catalysts, which can therefore largely expand the applications of nanomaterials in catalysis.

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