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Saintes-Maries-de-la-Mer, France

Lobry E.,Upper Alsace University | Jasinski F.,Upper Alsace University | Penconi M.,CNRS Laboratory for Molecular and Photochemical Reactions | Chemtob A.,Upper Alsace University | And 4 more authors.
Green Processing and Synthesis | Year: 2014

We show the potential of miniemulsion photopolymerization for the continuous production of aqueous poly(acrylate) dispersions in a microreactor at room temperature. 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 through-cure in turbid medium. Two key features prove that this process design is highly eco-efficient: i) two types of energy-saving and compact UV sources (fluorescent or light-emitting 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 parameters - flow rate, photo-initiator type/concentration, droplet size, solid content, UV source - on the photopolymerization course (kinetics) and the properties of the nanolatex obtained (particle size and molecular weight). © 2014 by De Gruyter 2014. Source


Lobry E.,Upper Alsace University | Jasinski F.,Upper Alsace University | Penconi M.,CNRS Laboratory for Molecular and Photochemical Reactions | Chemtob A.,Upper Alsace University | And 4 more authors.
RSC Advances | Year: 2014

An efficient continuous synthesis of nanolatex was achieved in water using a single-lane photochemical microreactor combined with an energy-saving and safe UV fluorescent lamp. Acrylate and thiol-ene miniemulsions were polymerized in high yields at low irradiance (3 mW cm-2) upon controlling droplet size, temperature and residence time. This journal is © the Partner Organisations 2014. Source


Jasinski F.,Upper Alsace University | Lobry E.,Upper Alsace University | Chemtob A.,Upper Alsace University | Croutxe-Barghorn C.,Upper Alsace University | Criqui A.,Mader Research MADER GROUP
Macromolecular Chemistry and Physics | Year: 2013

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 coefficient, comparable with that in solution. In contrast, a droplet-size decrease causes a significant and progressive reduction of the scattering coefficient, with a positive effect on light penetration. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Lobry E.,Upper Alsace University | Jasinski F.,Upper Alsace University | Penconi M.,CNRS Laboratory for Molecular and Photochemical Reactions | Chemtob A.,Upper Alsace University | And 5 more authors.
Macromolecular Chemistry and Physics | Year: 2014

Low-scattering monomer miniemulsions have recently emerged as a suitable system for the development of efficient photopolymerization processes in dispersed media. Since their reactivity under UV exposure is strongly dependent on their optical properties, there is a strong interest to find simple analytical methods for studying absorption and scattering with ready-to-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-flux theory of Kubelka-Munk on these multiple scattering miniemulsions enables the determination of the scattering and absorption coefficients for different initial droplet sizes. These results show that reaction kinetics are strongly correlated with scattering efficiency. Below a threshold average diameter of ca. 150 nm, any decrease of droplet size diminishes the extent of scattering significantly, 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. Studying the optical properties of concentrated miniemulsions prior to and during UV irradiation provides a wealth of information on their photopolymerization efficiency and nucleation process. For example, after a short UV exposure (3 min) causing a complete polymerization, an acrylate miniemulsion with an average droplet diameter of 40 nm causes much less scattering. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Jasinski F.,Upper Alsace University | Lobry E.,Upper Alsace University | Tarablsi B.,Upper Alsace University | Chemtob A.,Upper Alsace University | And 3 more authors.
ACS Macro Letters | Year: 2014

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%). (Chemical Equation Presented). © 2014 American Chemical Society. Source

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