Emeline Lobry | Institut National Polytechnique de Toulouse (original) (raw)

Papers by Emeline Lobry

OATAO is an open access repository that collects the work of Toulouse researchers and makes it fr... more OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible.

Chemical Engineering Journal, 2015

Chemical Engineering Science, 2011

Chemical Engineering Journal, 2013

Macromolecular Chemistry and Physics, 2014

Low-scattering monomer miniemulsions have recently emerged as a suitable system for the developme... more Low-scattering monomer miniemulsions have recently emerged as a suitable system for the development of effi cient photopolymerization processes in dispersed media. Since their reactivity under UV exposure is strongly dependent on their optical properties, there is a strong interest to fi nd simple analytical methods for studying absorption and scattering with readyto-polymerize concentrated miniemulsions, while avoiding dilution. This paper focuses on three types of concentrated miniemulsions without photoinitiator (PI) and containing either a hydrophilic or hydrophobic PI. The application of the two-fl ux theory of Kubelka-Munk on these multiple scattering miniemulsions enables the determination of the scattering and absorption coeffi cients for different initial droplet sizes. These results show that reaction kinetics are strongly correlated with scattering effi ciency. Below a threshold average diameter of ca. 150 nm, any decrease of droplet size diminishes the extent of scattering signifi cantly, thus improving light penetration and the reaction rate. Additionally, a complementary dynamic study proves that the smallest miniemulsions are subjected to a decrease of scattering during irradiation. This result opens up interesting perspectives on the elucidation of the nucleation mechanism operating in a miniemulsion photopolymerization.

Journal of Polymer Science Part A: Polymer Chemistry, 2014

The use of UV light to initiate emulsion polymerization processes is generally overlooked, whilst... more The use of UV light to initiate emulsion polymerization processes is generally overlooked, whilst extensive literature exists on photocuring of monomer films. In this study, the unique potential of UV light to produce at ambient temperature polyacrylate latexes without initiator was exploited. Although radical initiators are utilized at low concentration, their cost, toxicity, and odor provide incentives for finding alternatives. Starting with concentrated (30 wt %) and low scattering acrylate miniemulsions (droplet diameter <100 nm), it was demonstrated that acrylate self-initiation can promote an efficient and fast photopolymerization in micrometer-scale reactor (spectrophotometric cell) and lab-scale photoreactor. Herein, all kinetic, colloidal, and mechanistic aspects involved in the self-initiation of acrylate miniemulsion were extensively examined to provide a complete picture. In particular, the effects of droplet size, initiating wavelength, optical path, and irradiance on the course of the polymerization were thoroughly discussed. A diradical self-initiation pathway is the most likely mechanism. V C 2014

Macromolecular Chemistry and Physics, 2013

In monomer miniemulsions, droplet size is a key parameter impacting the optical properties, and c... more In monomer miniemulsions, droplet size is a key parameter impacting the optical properties, and consequently their photopolymerizability under UV light. Three simple spectrophotometric methodologies are developed, based on an integrating sphere, to evaluate precisely the effect of droplet size on radiation absorption and scattering, which both contribute to light attenuation. Using a series of diluted acrylate monomer miniemulsions ranging from 40 to 300 nm, all the methods converge toward a constant absorption coeffi cient, comparable with that in solution. In contrast, a droplet-size decrease causes a signifi cant and progressive reduction of the scattering coeffi cient, with a positive effect on light penetration.

Colloid and Polymer Science, 2014

When finally processed to provide the function for which the latex was selected-binding, protecti... more When finally processed to provide the function for which the latex was selected-binding, protecting, finishing-components such as surfactant, costabilizer or initiator become generally useless, not to say detrimental. In this study, we show that miniemulsion photopolymerization provides a suitable method to create latex without the apparent addition of these three compounds. Indeed, UV-driven monomer self-initiation can create initiating radicals without the aid of initiator, the fast in situ photogenerated polymer can hinder Ostwald ripening with the assistance of external costabilizer, and finally, UV-transparent clay can replace conventional surfactant to ensure colloidal stabilization. Each strategy has been developed individually before being combined together to end up with a unique miniemulsion procedure free of initiator, costabilizer and surfactant. Such approach paves the way to a simplified and environmentally improved pathway towards aqueous polymer dispersions.

Photochem. Photobiol. Sci., 2015

Oil-in-water miniemulsions containing a mixture of monomers as the dispersed organic phase have b... more Oil-in-water miniemulsions containing a mixture of monomers as the dispersed organic phase have been shown recently to be promising media for the development of photoinitiated polymerization processes. Albeit a crucial factor for a successful application, the efficiency of light absorption by the photoinitiator in these highly scattering systems is difficult to evaluate. In this work, a well-characterized water insoluble chemical actinometer (DFIS) replaced the oil-soluble photoinitiator, and was used as a probe and a model for UV light absorption in miniemulsions of variable droplet sizes and organic phase compositions (i.e. at different levels of scattered light). In the first step, the photon flux absorbed by the actinometer was determined in model miniemulsions based on an inert solvent (ethyl acetate), at a low oil phase content (3.0-6.0 wt%). For these low to moderately scattering systems, the photon flux absorbed by the actinometer in the miniemulsions was comparable to that in a homogeneous solution of ethyl acetate. In the second step, the absorbed photon flux was investigated in photopolymerizable miniemulsions (a mixture of acrylate monomers as oil phase). Surprisingly, in spite of much higher scattering coefficients than those found for ethyl acetate based miniemulsions of otherwise the same composition, the photon flux absorbed by the actinometer in photopolymerizable miniemulsions showed only a small decreasing trend. Such a result may be considered favorable for the further development of applications of photopolymerizations in miniemulsions.

Green Processing and Synthesis, 2014

We show the potential of miniemulsion photo polymerization for the continuous production of aqueo... more We show the potential of miniemulsion photo polymerization for the continuous production of aqueous poly(acrylate) dispersions in a microreactor at room tem perature. While the starting acrylate nanoemulsions are amenable to limit scattering, their polymerization within a microreactor provides additionally small microchannels and short diffusion path enabling an efficient mixing in order to alleviate the constraints associated with non uniform throughcure in turbid medium. Two key features prove that this process design is highly ecoefficient: i) two types of energysaving and compact UV sources (fluo rescent or lightemitting diode) were employed; ii) high conversions were achieved using the fluorescent lamp with short residence times (10 min), low irradiance (3 mW cm 2 ) and without the need of solvent. The present study describes briefly the influence of various parametersflow rate, photoinitiator type/concentration, droplet size, solid content, UV source -on the photopolymeriza tion course (kinetics) and the properties of the nanolatex obtained (particle size and molecular weight).

ACS Macro Letters, 2014

Historically, the synthesis of aqueous polymer dispersions has focused on radical chain-growth po... more Historically, the synthesis of aqueous polymer dispersions has focused on radical chain-growth polymerization of low-cost acrylate or styrene emulsions. Herein, we demonstrate the potential of UV-initiated thiol−ene step-growth radical polymerization, departing from a nontransparent difunctional monomer miniemulsion based on ethylene glycol dithiol and diallyl adipate. Performed without solvent and at ambient conditions, the photopolymerization process is energy-effective, environmentally friendly, and ultrafast, leading to full monomer consumption in 2 s, upon irradiating a miniemulsion contained in a 1 mm thick quartz cell microreactor. The resultant linear poly(thioether ester) particles have an average diameter of 130 nm. After water evaporation, they yield a clear elastomeric film combining chemical resistance and high degree of crystallinity (55%).