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International audience; Cationic latexes with T g s ranging between −40°C and 120°C were synthesised using n-butyl acrylate (BA) and/or methyl methacrylate (MMA) as the core polymers. Reversible addition-fragmentation chain transfer (RAFT) combined with polymerisation-induced self-assembly (PISA) allowed for in situ chainextension of a cationic macromolecular RAFT agent (macroRAFT) of poly(N-[3-(dimethylamino)propyl] methacrylamide) (PDMAPMA), used as stabiliser in so-called surfactant-free emulsion polymerisation. The resulting narrowly distributed nanosized latexes adsorbed readily onto silica surfaces and to model surfaces of cellulose nanofibrils, as demonstrated by quartz crystal microbalance with dissipation monitoring (QCM-D) measurements. Adsorption to anionic surfaces increased when increasing ionic strength to 10 mM, indicating the influence of the polyelectrolyte effect exerted by the corona. The polyelectrolyte corona affected the interactions in the wet state, the stability of the latex and re-dispersibility after drying. The QCM-D measurements showed that a lower T g of the core results in a more strongly interacting adsorbed layer at the solid-liquid interface, despite a comparable adsorbed mass, indicating structural differences of the investigated latexes in the wet state. The two latexes with T g below room temperature (i.e. PBA Tg-40 and P(BA-coMMA) Tg3) exhibited film formation in the wet state, as shown by AFM colloidal probe measurements. It was observed that P(BA-coMMA) Tg3 latex resulted in the largest pull-off force, above 200 m Nm −1 after 120 s in contact. The strongest wet adhesion was achieved with PDMAPMAstabilized latexes soft enough to allow for interparticle diffusion of polymer chains, and stiff enough to create a strong adhesive joint. Fundamental understanding of interfacial properties of latexes and cellulose enables controlled and predictive strategies to produce strong and tough materials with high nanocellulose content, both in the wet and dry state. † Electronic supplementary information (ESI) available. See

Copolymerization of isoprene (IP) with glycidyl methacrylate (GMA) was performed under RAFT (reversible addition-fragmentation chain-transfer) polymerization conditions in a platform for high-output experimentation. Covering the range between 1 and 0.2 molar fraction of IP in the feed, four sets of reactions were carried out at 10, 15, 20, and 30 h at 115 °C. The kinetic data obtained were used to estimate the reactivity ratios using a nonlinear least-squares approach (NLLS). Reactivity ratios rGMA = 0.61 and rIP = 0.74 indicate that both monomers tend to crosspropagate in agreement with known literature values. Concerning the RAFT study, relatively good control and livingness of the copolymerization was observed except for the experiment in which IP represents 20 mol % in the feed. 1H NMR characterization confirmed the presence of both monomers in the final copolymer, particularly the presence of the epoxy ring of GMA which is susceptible to post polymerization reactions. Finally, preliminary results on the hydrogenation of various polymers are discussed.

International audience; After a brief history that positions polymerizationinduced self-assembly (PISA) in the field of polymer chemistry, this review will cover the fundamentals of the PISA mechanism and review some features and limitations of RAFT-mediated PISA in terms of the choice of the components involved, the nature of the nano-objects that is achievable, the morphologies that are accessible and how they can be controlled, and some potential applications. This review will be part of the forthcoming second edition of 'The Handbook of RAFT' (Wiley, co-edited by G. Moad, E. Rizzardo, S.H. Thang) as a comprehensive chapter on RAFTmediated PISA.

International audience; • 4VP is an efficient controlling comonomer for NMP of MMA and PEOMA. • 4VP is unable to control the NMP of methacrylic acid. • Successful formation of 4VP-based block copolymers by chain extension. • Chain extension in the presence of silica particles yields raspberry-like composite colloids. A B S T R A C T The controlled polymerization of methacrylic monomers by nitroxide-mediated polymerization (NMP) still represents a challenge in polymer science. This issue can be circumvented by the addition of a small amount of a comonomer known to exhibit a controlled character in NMP, the most representative example being styrene. The purpose of this work is to explore the use of 4-vinyl pyridine (4VP) as controlling comonomer, while conferring at the same time some functionality to the polymer chains. The NMP of methyl methacrylate (MMA), poly (ethylene glycol) methyl ether methacrylate (PEOMA 950 , M n = 950 g mol −1) and methacrylic acid (MAA) using a small amount of 4VP under mild experimental conditions (< 90 °C, atmospheric pressure), was investigated in this work. The copolymerization of MMA or PEOMA 950 with 10 mol% 4VP, mediated by the use of the BlocBuilder ® alkoxyamine and a small amount of free nitroxide SG1, exhibited all the features of a controlled system in agreement with the favored incorporation of 4VP at the chain ends, leading to an efficient deactivation of the propagating radicals by the nitroxide SG1. In contrast, the polymerization of MAA was uncontrolled in the same conditions likely due to acid/base interaction between MAA and 4VP, affecting the reactivity of the functional comonomer. Consistently, the copolymerization of MAA with MMA also led to a progressive loss of control as the MAA content in the feed was increased. Among all the polymers synthesized, the P(MMA 72-co-4VP 10)-SG1 macroalkoyamine was then successfully used to reinitiate the copolymerization of n-butyl metha-crylate (BMA) and 4VP both in solution and via dispersion polymerization in a mixture of ethanol and water. Finally, raspberry-like polymer/silica composite particles were prepared through nitroxide-mediated dispersion polymerization performed in the presence of silica nanoparticles, taking benefit of the strong acid-base interaction between 4VP and silica.

International audience; Particle coagulation, in conjunction with nucleation and growth, plays a significant role in determining the evolution of particle size distribution in emulsion polymerizations. Therefore, many modelling and experimental studies have been carried out to have a better understanding and control of the particle coagulation phenomenon in order to achieve high-quality as well as highly efficient industrial production. This article presents a review of modelling and experimental studies focused on the particle coagulation phenomenon in emulsion polymerizations. The state-of-art of particle coagulation modelling pertaining to emulsion polymerizations is discussed. Experimental studies concerned with latex coagulation processes are summarized next. The review finishes by discussing outstanding problems that need attention and sharing our perspectives on future developments.

International audience; The corrosion of copper and silver in sulphide environments was assessed by several analytical techniques to investigate the influence of each one on the corrosion of sterling silver. The surface colour changes with the immersion time due to the formation of corrosion products composed of particles with distinct sizes and shapes and the consequent layer thickening. Ag 2 S is the main corrosion product of silver. At early stages of corrosion, Cu develops Cu 2 O and Cu 2 S, and later Cu 2 O again. After the corrosion of sterling silver, pure Cu and Ag are compared, and the predominant influence of Cu at the first stages may be suggested whilst Ag mainly contributes to longer corrosion stages. The layer-by-layer corrosion structure observed for the sulphidation of sterling silver was not observed for its constituent elements.

A framework, consisting of a computational fluid dynamics (CFD) simulation model coupled to a population balance model (PBM) is developed to study the effect of various parameters on the performance of an emulsion polymerization process which leads to the production of a fine dispersion of polymer particles in a continuous aqueous medium.Like most polymer products, latexes are “products-by-process”, whose main properties are determined during polymerization. One of the main parameters influencing the final quality of the latexes is the particle size distribution (PSD). Modeling the evolution of PSD is usually accomplished through the addition of a set of PBEs to the kinetic model. PBE provides a means of considering the contribution of different phenomena in the PSD evolution, being nucleation, growth of polymer particles by polymerization, and coagulation of particles due to brownian or fluid motion (Perikinetic and Orthokinetic coagulation, respectively).To assess the impact of nonhomogeneous mixing and physical parameters of the system on the evolution of the latex PSD, the transient simulation of flow was performed with the aid of a commercial CFD Package (Fluent® 15.0) to provide in each time step, the local concentrations of ionic species (to determine the rate of perikinetic coagulation modeled by DLVO model) and certain hydrodynamic parameters such as turbulence dissipation rate and shear rate (to determine the rate of orthokinetic coagulation). This information is applied simultaneously by the PBE add-on module of Fluent to calculate the PSD for the next time step; thus a complete coupling between CFD and PBM is assured; Un système consistant d'une simulation de mécanique des fluides numérique (MFN) couplée à un modèle de bilan de population (PBM) est développé afin d'étudier l'effet des paramètres variés sur la performance d'un procédé de polymérisation en émulsion qui conduit à la peoduction des particules de polymère dans un milieu aqueux continu.Comme une grande gamme des produits polymériques, des latexes sont les « produits par processus » (products-by-process), et leurs propriétés sont déterminés pendant la polymérisation. LA distribution de la taille des particules (PSD) est une des plus importants paramètres qui influence la qualité finale de latex. La modélisation d'évolution du PSD est généralement réalisée par l'addition un ensemble des PBEs au modèle cinétique. Le PBE fournit un moyen d'étudier la contribution des différents phénomènes dans l'évolution du PSD, comme la nucléation, la croissance des particules par la polymérisation, et la coagulation des particules à cause du mouvement brownien ou le mouvement du fluide (la coagulation Perikinetic et Orthokinetic, respectivement).Afin d'évaluer l'impact du mélange non homogène et les paramètres physiques du système sur l'évolution du PSD du latex, la simulation transitoire d'écoulement à été réalisé avec l'aide d'un progiciel commercial de MFN (Fluent® 15.0) pour munir dans chaque pas du temps, les concentrations locales des espèces ioniques (pour déterminer le taux de la coagulation Perikinetic modelé par le modèle de DLVO) ainsi que certains paramètres hydrodynamiques comme le taux de dissipation de la turbulence et le taux de cisaillement (afin de déterminer le taux de la coagulation Orthokinetic). Cette information est appliquée simultanément par le module complémentaire de PBM dans Fluent pour calculer le PSD pour le prochain pas du temps ; ainsi, un couplage complet entre le MFN et le PBM est assuré

International audience; The successful incorporation of a NCO-terminated polyurethane (PU) prepolymer in a hybrid miniemulsion is described with the purpose to develop waterborne, high solids, acrylic-PU hybrid nanoparticles to be used in pressure-sensitive adhesive (PSA) applications. To ensure efficient chemical incorporation of the reactive PU into the hybrid latex particles, the NCO moieties were reacted with 2-hydroxyethyl methacrylate (HEMA). The NCO-HEMA coupling reaction was thoroughly studied by conductimetry in order to control the extent of HEMA. incorporation into the PU chains. The resulting HEMA-end-capped prepolymers were chain extended in situ with Bisphenol A (BPA) and polymerized with n-butyl acrylate, methyl meth acrylate, and acrylic acid in the presence of small amounts of a chain transfer agent to form PU/acrylic particles. The amount of chain transfer agent, the ratio between HEMA and BPA, and the amount of PU were varied step by step to study their influence on the final film properties. The miniemulsions and resulting hybrid latexes were characterized in terms of size, monomer conversion, evolution of the ratio of the number of polymer particles to the number of droplets (N-p/N-d), and gel content. In parallel, the mechanical and adhesive properties of the films were tested using probe tack experiments. This allowed us to identify the reaction conditions making it possible to obtain high solids content PU/acrylic hybrid latexes, usable to prepare waterborne pressure-sensitive adhesive films with good adhesive properties, using a simple miniemulsion polymerization method.

A computational framework, consisting of a laminar computational fluid dynamics (CFD) simulation model coupled to a multizonal population balance, is developed to assist in the scale-up of high-solid-content (HSC) latex production and processing. Poly3D CFD software is used to generate flow fields inside a series of reactors; this information is then sent to the process model to assess the impact of nonhomogeneous mixing on the evolution of the latex particle size distribution (PSD) when concentrated latex suspension is altered via the addition of a coagulant. As the general shape of the PSD evolves, the model monitors changes in the rheological parameters in each zone of the reactor; the flow field is recomputed if a significant change in any of the properties is detected. The details of the framework are presented and its utility is demonstrated. Preliminary results indicate that nonhomogeneity inside the reactor will have an effect on the final latex PSD obtained.

A poly(ethylene oxide)-based macromolecular agent for reversible addition-fragmentation chain transfer (PEO-RAFT, 2 000 g·mol−1) was synthesized and used as a stabilizer and a control agent in the miniemulsion polymerization of styrene. Using 2,2′-azobis(isobutyronitrile) as initiator, stable polystyrene (PS) particles sterically stabilized by the PEO segments were obtained with almost complete conversion after 22 h. Molar masses increased linearly with conversion although rather broad molar mass distributions were obtained due to the presence of several populations of PEO-b-PS block copolymers. However, dynamic light scattering analyses showed a significant increase in particle diameter with conversion and the ratio of the number of particles to the number of droplets (Np/Nd) was thus lower than one indicating that the system did not follow a true miniemulsion process. Transmission electron microscopy additionally revealed the presence of holes inside the formed particles suggesting that block copolymer ...

Nucleoside analogues (NAs) are important agents in the treatment of hematological malignancies. They are prodrugs that require activation by phosphorylation. Their rapid catabolism, cell resistance and overdistribution in the body jeopardize nucleoside analogue chemotherapy. Accordingly, therapeutic doses of NAs are particularly high and regularly have to be increased, resulting in severe toxicity and narrow therapeutic index. The major challenge is to concentrate the drug at the tumour site, avoiding its distribution to normal tissues. New drug carriers and biomaterials are being developed to overcome some of these obstacles. This review highlights novel NA delivery systems and discusses new technologies that could improve NA cancer therapy.

Hydrophilic (co)polymers carrying a thiocarbonyl thio end group such as poly(dimethylaminoethyl methacrylate), poly(ethylene oxide), and poly(ethylene oxide)-block-poly (dimethylaminoethyl methacrylate) have been evaluated as precursors of stabilizers in batch ab initio emulsion polymerization of styrene under acidic conditions to form electro-sterically stabilized polystyrene latex particles. As a mixture of P(DMAEMA/H + Cl - )-RAFT and PEO-RAFT failed to give satisfactory results, PEO-RAFT was used as a control agent for the RAFT polymerization of DMAEMA, and the resulting block copolymer was successfully used in ab initio styrene emulsion polymerization.

A multi-scale modelling approach is proposed as a means of eventually overcoming the limitations of the multigrain and polymer flow models of particle growth. It is demonstrated that there is a need to introduce some sort of macroheterogeneity into the evolution of the stress build-up in the growing macroparticles in order to see a local rupture of the particle structure. Different simulations are proposed and qualitatively compared to previously published experimental results in order to validate the approach.

Polyolefins account for more than half of worldwide production of thermoplastics. The majority is used as commodity polymers but they may also provide the starting backbones for original architectures. Most polyolefins are obtained by catalytic polymerization and this powerful technique may be used to produce polyolefins incorporating interesting functional groups that can serve as initiating sites for other successively applied polymerization techniques. This review describes the state of the art in strategies employing catalytic olefin polymerization followed by a living or controlled polymerization. The latter methodologies are classified according to the living/controlled polymerization technique used including anionic polymerization, nitroxide-mediated radical polymerization (NMRP), atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain transfer (RAFT).

A detailed investigation of the kinetics, morphology and polymer properties observed during the polymerisation of ethylene on a Ziegler-Natta catalyst at very short times (t 40 ms) in a novel, quenched-flow reactor is presented. It was found that for times shorter than a tenth of a second, the observed rate of polymerisation was significantly higher than expected, and that the crystallinity of the nascent ethylene homopolymer was of the order of 25 to 30% - much lower than expected. Evidence is presented that shows that fragmentation is essentially complete in a small fraction of a second.

The nonlinear rheological behavior of different monomodal and bimodal polystyrene model latices has been investigated. The objective of the present work is to develop a practical approach for the modeling of the evolution of the viscosity of bimodal latices based only on the experimental behavior of related monomodal components. For this purpose, the viscosity curve of monomodal latices is described using the Carreau–Yasuda in order to obtain a phenomenological depiction of the shear thinning behavior. Following this, the Carreau–Yasuda law was extended to describe the complex viscosity behavior of bimodal latices. The parameters of the Carreau–Yasuda model, i.e., the zero shear viscosity η0, the high shear viscosity η∞, and the inverse of the onset of shear-thinning τ (τ=1∕γc) are expressed from the Krieger–Dougherty equation. The extension of the Krieger–Dougherty equation to bimodal latices is based on the porosity model developed by Ouchiyama and Tanaka [Ind. Eng. Chem. Fundam. 23, 490–493 (1984)], a...

This work describes the elaboration of polymer/iron oxide (IO) hybrid latexes through surfactant-free emulsion polymerization. Cationic iron oxide nanoparticles stabilized by nitrate counterions were first synthesized by the co-precipitation of iron salts in water. Magnetic hybrid latexes were next obtained by two polymerization routes carried out in the presence of IO. The first route consists in the synthesis of polymer latexes armored with IO via Pickering emulsion polymerization of methyl methacrylate (MMA) or styrene (St). An auxiliary comonomer (namely methacrylic acid, acrylic acid or 2-acrylamido-2-methy-1- propane sulfonic acid) was used to promote IO particle adhesion to the surface of the generated polymer particles. TEM showed the presence of IO at the surface of the polymer particles and the successful formation of IO-armored polymer particles. TGA was used to quantify the IO incorporation efficiency, which corresponds to the fraction of IO effectively located at the particle surface. The incorporation efficiency increased with increasing the amount of auxiliary comonomer, suspension pH and IO content or with increasing monomer hydrophobicity. In the second route, IO encapsulation was investigated via reversible addition-fragmentation chain transfer (RAFT)-mediated emulsion polymerization. The developed strategy relies on the use of water-soluble amphipathic macromolecular RAFT agents containing carboxylic acid groups, designed to interact with IO surface. The interaction between the macroRAFT agents and IO was investigated by the study of the adsorption isotherms. Both DLS and SAXS measurements indicated the formation of dense IO clusters. These clusters were then engaged in the emulsion polymerization of St or of MMA and nbutyl acrylate (90/10 wt/wt) to form a polymer shell at their surface. Both IO-armored latex particles and polymer-encapsulated clusters display a superparamagnetic behavior; Ce travail de thèse décrit l'élaboration de latex hybrides oxyde de fer (OF)/polymère par polymérisation en émulsion sans tensioactif. Des nanoparticules d'OF cationiques ont été tout d'abord synthétisées par co-précipitation de sels de fer dans l'eau. Des latex hybrides magnétiques ont été ensuite obtenus par deux voies de polymérisation. La première consiste en la synthèse de particules de latex de morphologie 'carapace' par polymérisation en émulsion Pickering du styrène et du méthacrylate de méthyle (MMA). Un comonomère auxiliaire (acide (méth)acrylique ou acide 2-acrylamido-2-méthyl-1-propane sulfonique) a été utilisé pour favoriser l'adsorption des OF à la surface des particules de polymère produites. Les analyses par MET indiquent la présence d'OF à la surface des particules de polymère (structure carapace). L'analyse thermogravimétrique a permis de quantifier l'efficacité d'incorporation des OF, i.e. la fraction d'OF initialement introduits effectivement adsorbés à la surface des particules. L'efficacité d'incorporation augmente avec la quantité de comonomère auxiliaire, le pH et la concentration en OF et dépend de la nature du monomère hydrophobe. Dans la deuxième voie, les OF ont été encapsulés par polymérisation radicalaire contrôlée par transfert de chaîne réversible par addition-fragmentation (RAFT) en émulsion aqueuse. La stratégie utilisée repose sur l'utilisation de macroagents RAFT amphiphiles comportant des groupements acide carboxylique connus pour interagir avec la surface des OF. L'interaction entre les macroRAFTs et les OF a été étudiée à travers le tracé de l'isotherme d'adsorption. Des analyses SAXS et DLS indiquent la formation de clusters d'oxyde de fer. Ces derniers ont été ensuite engagés dans la polymérisation en émulsion du styrène ou d'un mélange de MMA et d'ABu (ratio massique : 90/10) pour former une écorce de polymère à leur surface. Les particules carapace et les OF encapsulés affichent un comportement superparamagnétique

Selective poisoning has been studied as a means of improving the morphology and rheological properties of high-impact poly(propylene) copolymer particles. Two different methods of poisoning the catalyst surface in order to avoid the accumulation of ethylene-propylene rubber (EPR) without influencing the reaction kinetics were tested: a slurry-phase poisoning step using ethylene glycol dimethyl ether between the homopolymerisation and copolymerisation reaction steps; and direct poisoning via the use of a commercial antistatic agent during the gas-phase copolymerisation reactor. It was observed that both methods eliminated the formation of rubber on the particle surface without noticeably influencing the kinetics. On the other hand, the use of the products directly in the gas-phase reaction also contributed to the reduction of static electricity. It can be concluded from these experiments that industrial antistatic agents derive at least part of their effect from poisoning of the active sites on the surface of the catalyst. Furthermore, it appears that in the case of the catalyst used in this study, EPR does not appear to flow out of the growing particles. Most of the EPR found at the surface of the particles is formed close to it.

Summary: A new method for the encapsulation of inorganic charges by an organic polymer by a reactive double emulsification process is proposed. This work is especially novel since it is highly unusual to encounter polymerization reactions in such a double emulsification process. Silica was first synthesized in cyclohexane using a sol–gel process in an inverse microemulsion in the presence of a non-ionic surfactant (nonylphenyl ether polyoxyethylene), tetraethoxysilane, and concentrated ammonia. The coupling agent, 3-aminopropyl triethoxysilane, was then grafted onto the surface of the silica nanoparticles. In a third step, direct miniemulsions were prepared from the microemulsion containing the functionalized silica nanoparticles. The miniemulsions were prepared using sodium dodecylsulfate as the surfactant and cetyl alcohol as the costabilizer. Finally, an interfacial polycondensation occurred between a diamine added to the external phase and sebacoyl chloride in solution in the dispersed phase. The formation of polyamide latexes was proven using infrared spectroscopy, and observation of the nanocomposites by transmission electron microscopy showed mean diameters of 100 nm. TEM micrograph of silica/polyamide nanocomposite particles

Accepted for publication in "Progress in Polymer Science" (10/05/05); A review of the use and limitations of Population Balance Equations (PBE) in the modeling of emulsion polymerisation (EP), and in particular of the particle size distribution of the dispersed system is presented. After looking at the construction of the general form of PBEs for EP, a discussion of the different approaches used to model polymerization kinetics is presented. Following this, specific applications are presented in terms of developing a two-dimensional PBE for the modeling of more complex situations (for example the particle size distribution, PSD, and the composition of polymerizing particles). This review demonstrates that while the PBE approach to modeling EP is potentially very useful, certain problems remain to be solved, notably: the need to make simplifying assumptions about the distribution of free radicals in the particles in order to limit the computation complexity of the models; and the reliance of full models on approximate coagulation models. The review finishes by considering the different numerical techniques used to solve PBEs.

A methacrylate-functionalized poly(ethylene glycol) macromonomer was copolymerized at the surface of methacrylate-derivatized maghemite nanoparticles. After silylation of the magnetic core with methacryloxypropyltrimethoxysilane, two grafting procedures based on either a direct copolymerization reaction in water or an inverse emulsion polymerization were compared. A direct copolymerization led to low polymer surface amounts, whereas an inverse emulsion process allowed nanocomposite particles containing up to 90 wt.-% polymer to be obtained.

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The grafting of poly(ethylene oxide) (PEO) onto silica nanoparticles was performed in situ by the ring-opening polymerization of the oxirane monomer initiated from the mineral surface using aluminium isopropoxide as an initiator/ heterogeneous catalyst Alcohol groups were first introduced onto silica by reacting the surfacic silanols with prehydrolyzed 3-glycidoxypropyl trimethoxysilane. The alcohol-grafted silica played the role of a coinitiator/chain-transfer agent in the polymerization reaction and enabled the formation of irreversibly bonded polymer chains. Silica nanoparticles containing up to 40 wt.-% of a hairy layer of grafted PEO chains were successfully produced by this technique.

In order to produce high solid content latexes in an unseeded process it is necessary to first begin by generating a concentrated latex with a monomodal particle size distribution and high solid contents. A process for the emulsion polymerisation of methyl methacrylate with butyl acrylate at solid contents of over 60% per unit volume is presented. The process relies on the use of an electrically neutral initiation system, combined with a stabilisation system rich in non-ionic surfactant. It was demonstrated that during the critical semi-batch growth stage, it is necessary to add the surfactant at a variable flow rate in order to avoid accumulating it in the water phase, and thereby ensuring that particles created by homogeneous nucleation are not stabilised. It is also shown that correctly adjusting the flow rate leads to a robust, reproducible process. Finally, a ‘stability band’ is clearly identified, and it is clear that the system is ‘self-regulating’ in the sense that an equilibrium between auto-flocculation and stabilisation of new particles leads to a latex with a surface coverage of 80–95% at high solid contents.

Polystyrene (PS)-grafted silica nanoparticles were prepared by nitroxide-mediated polymerization of styrene using N-tert-butyl-N-[1-diethylphosphono(2,2-dimethylpropyl)] nitroxide (DEPN) as mediator. Two routes were investigated to graft the alkoxyamine initiator onto silica. In the first route, (acryloxypropyl)trimethoxysilane (APTMS) was covalently attached to silica and the alkoxylamine was formed in situ by spin trapping the acryloxy radicals produced by reaction of azobisisobutyronitrile (AIBN) with the grafted APTMS molecules using DEPN as radical trap. In the second route, the surface alkoxyamine initiator was produced in a one-step process by reacting simultaneously DEPN, AIBN, and APTMS in the presence of silica. Next, polystyrene chains with controlled molecular weights and narrow polydispersities were grown from the alkoxyamine-functionalized nanoparticle surface. The amount of polystyrene grafted to the surface was determined by thermogravimetric analysis, and was found to increase with increa...

The use of miniemulsions of styrene and butyl acrylate to make high-solid-content, low-viscosity latices was investigated. Products were obtained with solid concentrations greater than 70 wt % and viscosities as low as 350 mPa s at shear rates of 20 s−1. This was possible with monomodal and bimodal latices. In addition, the compartmentalization of the reactive species in the miniemulsion systems was exploited to produce latices with high solid concentrations, low viscosities, and bimodal molecular weight distributions. This demonstrated a potentially interesting application for this sort of material. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 745–752, 2005

An attempt was made to analyse the partitioning of anionic surfactants in a mixed surfactant system using surface tension and conductivity measures. This last technique gives us access to the quantity of free ions in solution, and thus a measure of the amount of anionic surfactant available in the aqueous phase. The range of surfactant concentrations studied here is such that the global surface coverage (assuming that the totality of the emulsifier is at the particle surface) varies around 100%.

Butyl acrylate/vinyl acetate/acrylic acid (BA/VAc/AA) emulsion latexes were produced in a semi-batch mode. The objective was to generate polymers with properties favoring their application as pressure-sensitive adhesives. The influence of the individual monomer concentrations on final properties such as glass transition temperature (T g ), peel strength, shear strength and tack was investigated. To obtain the maximum amount of information in a reasonable number of runs, a constrained three-component mixture design was used to define the experimental conditions. Latexes were coated onto a polyethylene teraphthalate carrier and dried. Different empirical models (e.g. linear, quadratic and cubic mixture models) governing the individual properties (i.e. T g , peel adhesion, shear resistance and tack) were developed and evaluated. In the given experimental region, no single model was found to fit all of response (i.e. the final properties). However, in all models the most significant factor affecting the final properties was the AA concentration, followed by the VAc concentration.

A Lewis acid surfactant combined catalyst (LASC) was tentatively used in a cationic polymerization in miniemulsion of p-methoxystyrene (pMOS). In a first part, the initiating potential of trisdodecyl sulfate ytterbium (Yb(DS)3, 0.25H2O) was evidenced in the solution polymerization of pMOS initiated by the corresponding chlorinated adduct pMOS−HCl. Miniemulsion polymerizations of pMOS performed using the same initiating system gave rise to oligomers, but experimental conditions chosen could not evidence the expected LASC-mediated cationic polymerization process. Further studies showed that LASC is located at the interface and acts only as a surfactant together with SDS. The polymerization occurred due to the hydrolysis of pMOS−HCl. The resulting acidification of the water phase leads to the transformation of SDS into its sulfuric acid form acting as an inisurf according to an interfacial cationic polymerization process. Latex particles of pMOS incorporating narrowly distributed low molar mass chains were o...

International audience; The living cationic polymerization of a saccharidic monomer (1,2:3,4-di-O-isopropylidene-6-O-(2-vinyloxyethyl)-D-galactopyranose, GVE) gives rise to aldehyde end-capped polymers (PGVE-CHO) of low molar masses (

The particle morphology of impact polypropylene was examined experimentally in order to understand how the rubber phase produced in the second step of the polymerisation is distributed inside the growing polymer particles, and how the quantity of rubber produced influences the overall morphology of the final product. It was found that the rubber can pool on the surface of the growing particles, but that this pooling is not uniform. In addition, it was observed that the rubber phase does not flow out of the large pore openings on the surface of the particles. A possible mechanism for the distribution of rubber was proposed. #An earlier version of this paper was presented at ECOREP II, 2nd European Conference on Reaction Engineering of Polyolefins, Lyon, France, July 1–4, 2002.

Different surfactant and costabilization systems were studied for the miniemulsion polymerizations of styrene (St) and of butyl methacrylate (BMA). It was found that the combination of sodium dodecyl sulfate, Triton X-405, and octadecyl acrylate yielded excellent results. With this system all of the droplets initially present in the reactor polymerized. This stabilization system was then used in the study of compartmentalization of the monomer droplets in miniemulsion polymerization. Blends of BMA and St miniemulsions were prepared separately and polymerized together to study mass transfer in this system. It was observed that no matter is exchanged between the different phases. This compartmentalization was also demonstrated and exploited by producing a bimodal molecular weight distributions latex, achieved with a semicontinuous process. The lower MWD was created by adding a second miniemulsion containing a transfer agent. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 115–124, 2004

International audience; Binary colloidal particles of polyhedral morphology, obtained by an emulsion polymerization of styrene in the presence of silica seeds, are studied. Because of kinetic effects, composite particles usually exhibit polydispersity in size, shape, and composition. Thus, accurate techniques aiming at characterizing the size and the shape, as well as the composition and surface properties of such objects, are required. In this work, we use charge detection mass spectrometry (CD-MS) as a tool for the characterization of nanometer-sized composite (clusters of) particles. CD-MS measures both the mass and the charge for each ion. This single ion mass spectrometry technique enables one to construct a histogram of mass, yielding the mass distribution. CD-MS for molar mass determination and composition of composite particles is demonstrated to be complementary to transmission electron microscopy. The study of the charging capacity of these composite particles in the gas phase also appears as a valuable approach to probe the surface area of such complex nano-objects, thus giving some insight about their structure and morphology.

A high-gain nonlinear cascade state estimator is presented in this work and used to monitor conversion and polymer composition in an emulsion copolymerization process. The advantage of this cascade observer is that it requires neither occasional online samples nor prior knowledge of the dependence of the overall heat-transfer coefficient with the solids content of latex. A simple test is used to ensure that the results are robust to process noise and to rapid changes in conditions during the semibatch phase. Applications of this technique are presented in both laboratory-scale and industrial pilot-scale reactors.

Following a previous work (J. L. Luna-Xavier et al., Colloid Polym. Sci.279, 947 (2001)), silica-poly (methyl methacrylate) (PMMA) nanocomposite latex particles have been synthesized in emulsion polymerization using a cationic initiator, 2,2'-azobis (isobutyramidine) dihydrochloride (AIBA), and a nonionic polyoxyethylenic surfactant (NP30). Silica beads with diameters of 68, 230, and 340 nm, respectively, were used as the seed. Coating of the silica particles with PMMA was taking place in situ during polymerization, resulting in the formation of colloidal nanocomposites with a raspberry-like or a core-shell morphology, depending on the size and nature of the silica beads. The amount of surface polymer was quantified by means of ultracentrifugation and thermogravimetric analysis as extensively described in the first article of the series (see above reference). The influence of some determinant parameters such as the pH of the suspension, the initiator, silica, monomer, or surfactant concentration on the amount of coating polymer and on the efficiency of the coating reaction was investigated in details and discussed in light of the physicochemical properties of the seed mineral. Electrostatic attraction between the positive end groups of the macromolecules and the inorganic surface proved to be the driving force of the polymer assembly on the seed surface at high pH, while polymerization in adsorbed surfactant bilayers (so-called admicellar polymerization) appeared to be the predominant mechanism of coating at lower pH. Optimal conditions have been found to reach high encapsulation efficiencies and to obtain a regular polymer layer around silica.

Inverse gas chromatography has been used to estimate the characteristic mass transfer time for diffusion of ethylene and propylene in polypropylene particles. It was found that the mass transfer time corresponded to a length scale that is the same order of magnitude as the particle diameter, dp (between 0.3 and 1 μm). Furthermore, when interpreted in terms of diffusion coefficients for spherical particles, these coefficients were found to be of the same order of magnitude and those measured elsewhere for diffusion in pure polymer. This implies that diffusion in the particles is controlled by diffusion in the polymer, and that previous descriptions of particle morphology used in modelling studies need to be revised. In addition, experimental evaluation of reaction rates has demonstrated that changing length scales due to particle agglomeration can also significantly reduce the observed activity in gas phase olefin polymerisation, and that the severity of the reduction in rate correlates with the severity of the agglomeration process.

Several different methods were used to evaluate the average particle diameter and the particle size distribution of different types of polymer latexes. Monomodal and bimodal latexes were tested with different instrumental methods. It was found that standard QELS methods were suitable for monomodal latexes. In the case of a bimodal latex, multiangle dynamic light scattering and separative methods offered adequate estimates of the average particle size of both populations, as well as of the relative quantities of each population in the final latex.

International audience; A controlled polymerisation of styrene has been achieved under ATRP conditions by using a phosphine-containing MoIII/MoIV system. Linearity of the Mn vs conversion plot and low PDI’s are observed in bulk, in a 30% (v/v) PhCl solution, and in a chain extension experiment when using MoCl3(PMe3)3/BIB. Controlled polymerisation is also observed for a reverse ATRP experiment starting from MoCl4(PMe3)3/AIBN. The absence of chain transfer and termination is confirmed by NMR and MALDI–TOF analyses of polymers obtained by employing BEB and BIB as initiators.; Cet article décrit la possibilité d'effectuer une polymérisation contrôlée du styrène en utilisant un système de complexes de coordination de MoIII/MoIV contenant des ligands phosphines. La propagation procède selon un mécanisme de transfert d'atome par voie radicalaire (ATRP) en utilisant le complexe MoCl3(PMe3)3 et l’amorceur PhCH(Br)CH3 (BEB). En effet, celui-ci a été prouvé par une série d'expériences : polymérisation en masse et en solution, essais d’extension de chaîne et de catalyse inverse (par utilisation du complexe MoCl4(PMe3)3 et une source de radicaux libres, le composé AIBN). Les résultats obtenus montrent une bonne linéarité des masses moléculaires en fonction du taux de conversion du monomère et les indices de polydispersités sont relativement faibles. Des analyses du polymère par RMN et MALDI-TOF-MS ont permis d'exclure la présence de transfert de chaîne et de terminaisons bimoléculaires au cours du processus.

A two-dimensional high gain observer has been constructed to estimate the reaction rate parameters in a laboratory scale stopped flow fixed bed reactor for gas phase ethylene polymerization. The observer is based on the heat balances of a validated model of the reactor and the measured variable is the outlet temperature of the fixed bed. To create an observable system of equations, the polymerization rate is considered in two parts, an activation energy term and a lumped parameter. The effective radial conductivity in the fixed bed and the heat-transfer coefficient at the wall are considered separately. The polymerization rate is calculated from the observer results and is in good agreement with the measured data and calculated values. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3511–3523, 2014

International audience; Conductive composites based on few layer graphene are of primary interests. In this work latex based composites were produced leading to a specific cellular morphology. Highly conductive graphene-based composite materials have been produced through a solvent-free procedure. Both the mechanical and conductivity behaviors were successfully described using a percolation approach that confirms the presence of a three dimensional filler network efficiently spread across the material. The influence of the aspect ratio between the conductive filler and the latex nanosphere drove the study. It was demonstrated experimentally that the tuning of the cell dimensions of the composite morphology influences the percolation threshold and the reachable maximum conductivity and reinforcement. These experimental results are consistent with phenomenological models based on the statistical percolation theory. (C) 2014 Elsevier Ltd. All rights reserved.

International audience

Silica/poly(methyl methacrylate) nanocomposite latex particles have been synthesized by emulsion polymerization of methyl methacrylate using a nonionic surfactant: nonylphenol poly(oxyethylene) and three different initiators, namely: 2,2′-azobis(2-amidinopropane) dihydrochloride (AIBA), potassium persulfate (KPS) and azobis(isobutyronitrile) (AIBN), being cationic, anionic and nonionic, respectively. A silica sol with an average diameter of 68 nm was used as the seed. The polymerization reaction was conducted under alkaline conditions in order to evaluate the role of the surface charge of the hydrophilic silica on the coating reaction. AIBA was found to be adsorbed on the silica surface owing to electrostatic interactions of the amidine function of the cationic initiator with the silanolate groups of the oxide surface, while the anionic and the nonionic initiators did not adsorb on silica under the same conditions. Nonetheless, whatever the nature of the initiator, polymerization took place on the silica particles as evidenced by transmission electron microscopy. The extent of interaction between the inorganic surface and the polymer particles was quantified by means of ultracentrifugation and a material balance. As much as 65% by weight of the total polymer formed was found to be present at the silica surface using AIBA, while only 40% for KPS and 25% for AIBN was found to cover the silica particles under alkaline conditions. We demonstrate that by using a cationic initiator and by controlling the pH of the suspension it is possible to significantly decrease the amount of free polymer. Coating of the silica particles took place through a kind of in situ heterocoagulation mechanism.

The interaction between mass transfer effects and morphology in heterogeneous olefin polymerization

A sequence of experimental steps was perfected to produce high-impact modified polypropylene (PP), and to study the influence of particle morphology and rubber content on the reaction kinetics, especially in terms of mass transfer limitations. It was found that after a critical copolymer content at approximately 40% (with respect to total weight), it was impossible to obtain high reaction rates. This is thought to be the result of a fundamental change in particle morphology attributed to the presence of a soft EPR copolymer phase in the micropores. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1047–1060, 2001

Measurements were made of the value of the lumped kinetic constant kp/k of vinyl acetate in different solvents and with different initiators. This quantity was evaluated using the well-known conversion vs. time approach in dilute solutions using both azo-bis-isobutyronitrile and benzoyl peroxide (AIBN and BPO), and two different solvents (toluene and ethyl acetate) at 60°C. As was found for butyl acrylate in Part 1 of this series, it was found that the value of the lumped rate constant depends very strongly on the concentration of monomer in solution, decreasing as the solution becomes more and more dilute. However, unlike butyl acrylate, vinyl acetate is much more susceptible to changes in the solvent type, with toluene acting as a severe retarding agent of polymerization. The results of the present study suggest that at least two separate effects of solvent exist simultaneously in the case of vinyl acetate polymerization, and that both of them must be taken into account when attempting to model this type of system. The number- and weight-average molecular weights of the different polymers were also measured, and excellent agreement was found between the measurements and model predictions. A linear relationship was shown to exist between the value of the lumped constant and the square root of the number-average chain length. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 589–601, 1999

The modelling of heat and mass transfer during the gas and slurry phase polymerisation of olefins is examined. It is demonstrated that it might not be necessary in many cases to calculate concentration gradients in the growing catalyst/polymer complex, and that the currently used representation of heat transfer from small, highly active particles using standard chemical engineering correlations might not be accurate. Close examination of the morphology of catalyst particles shows that it is unlikely that the particles should be treated as a pseudo-homogeneous medium, and in fact the critical length scale for mass transfer is not the particle radius, but is much smaller. Furthermore, computational fluid dynamic simulations of single and interacting particles shows that convection is not the dominant heat transfer mechanism during the critical stages of the reaction.

Physical property data for the system ethylene/butene/polyethylene are presented for both high and low density polyethylene (PE) samples. A simple Flory Huggins model is shown to be satisfactory for the estimation of the solubility (in the amorphous fraction of the polymer) of both monomers in PE, with χ equal to 0.3 for ethylene and 0.5 for butene. No co-solubility effects of butene on ethylene were found for the relatively low partial pressures of butene used in this study (0.65 bars/21 bars). However, DSC analyses of the polymer samples used in the cosolubility experiments showed an irreversible reduction of the overall crystallinity after exposure to butene. Crystallinity data as a function of temperature are also presented for a variety of low PE samples, along with data on the melting point ( T m ) as a function of butene content. Both quantities were observed to decrease as a function of increasing butene content, and an empirical relationship between the butene fraction of a PE sample and T m is proposed.

An experimental investigation of mass transfer limitations on a single batch of high activity, heterogeneous catalysts used in the slurry polymerization of ethylene is presented. The viscosity of the continuous phase was varied, using trace amounts of inert copolymer in order to reduce the monomer diffusivity, and the activity levels were varied using hexene as an activator. These changes were intended to clearly identify situations in which the polymerization becomes mass-transfer-limited due to diffusion resistance in the pores of the catalyst. Increasing the observed activity of the catalyst from approximately 9000 to 40,000 grams of polymer per gram of catalyst per hour (g/g/h) revealed no evidence of mass transfer resistance, even when the diffusivity of the monomer in solution was reduced by a factor of six. Analysis of the molecular weight as a function of particle size supported this conclusion but did suggest that there might be slight chemical differences between large and small particles.