International audiencePolyurethanes (PUs) constitute a popular class of plastic materials with a wide range of applications in construction, coatings, and the automotive industry. PUs are usually synthesized by step-growth polymerization and, therefore, exhibit non-uniform molecular structures. Here, we show that uniform PUs can be prepared by a facile chemoselective multistep-growth approach. This strategy permits precise control of the chain lengths of the PUs formed and their primary structure, thus making the preparation of coded monomer sequences possible. Furthermore, it was found that these polymers are remarkably easy to analyze by tandem mass spectrometry sequencing. Thus, these precision polymers can potentially be used as molecular barcodes in various applications. As a proof of concept, their use as anti-counterfeiting tags for identification of materials is reported here

Polyurethanes based on vegetable oil were synthesized with castor oil and toluene diisocyanate, isophorone diisocyanate or hexamethylene diisocyanate, using dibutyltin dilaurate as a catalyst. The effects of the nature of the diisocyanate on the evolution of the kinetics, as well as the physical and mechanical properties and the thermal stability, of the different synthesized polyurethanes were investigated, and these complement data from the literature on equivalent systems. The polymerization kinetics, degree of swelling and mechanical properties were greatly affected by the diisocyanate nature, whereas the rheological properties and thermal stability were found to be similar for all polyurethanes.magnified image

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An easy assembling-disassembling co-axial capillaries microfluidic device was built up for the production of double droplets. Uniform polymer core-polymer shell particles were synthesized by polymerizing the two immiscible monomer phases composing the double droplet. Thus poly(acrylamide) core-poly(tri(propylene glycol) diacrylate) shell particles with controlled core diameter and shell thickness were simply obtained by adjusting operating parameters. An empirical law was extracted from experiments to predict core and shell sizes. Additionally uniform and predictable non-spherical polymer objects were also prepared without adding shape-formation procedures in the experimental device. An empirical equation for describing the lengths of rod-like polymer particles is also presented.

Monodisperse and size-controlled spherical polymer particles were synthesized by in situ photopolymerization of O/W monomer emulsions. Monomer droplets were produced without surfactant or pretreatment at a needle tip in a simplified axisymmetric microfluidic device. The effect of the viscosity of the continuous phase on the particle size was studied. The system operated in the dripping mode, at a low Reynolds number. A dimensionless master curve describes the particle diameter as a function of the needle inner diameter as well as velocity and viscosity ratios of continuous and dispersed phases. An empirical law predicts the particle size. The normalized particle diameter depends upon the ratio of the capillary numbers of continuous and dispersed phases with an exponent equal to -0.22.

International audienceSequence-coded polyurethanes were tested as anti-counterfeiting tags for the labelling of methacrylate-based intraocular implants. These sequence-defined oligomers were prepared by solid-phase iterative chemistry using two comonomers allowing formation of a controlled 0/1 binary sequence. Tags with different sequences and chain-lengths were synthesized and tested for lenses labeling. Two main methods were investigated for incorporating the tags in the intraocular implants. In a first approach, they were included in situ during the free-radical copolymerization of 2-ethoxyethyl methacrylate and ethylene glycol dimethylacrylate. In another strategy, premade lenses were swollen in a THF solution containing the polyurethane tags and dried. Both approaches allowed successful incorporation of the polyurethane labels in the methacrylate networks. In order to demonstrate this, the tags were extracted from the lenses using a solvent swelling protocol and analyzed by electrospray mass spectrometry. In all cases, the labels were found and their coded sequences could be identified by tandem mass spectrometry sequencing. These results indicate that sequence-coded polyurethane tags represent a valid option for the labeling of implants. Importantly, it was shown in this work that the use of small weight fractions of polyurethane tag (i.e. 0.1-0.4 wt%) do not alter significantly the biocompatibility and transparency properties of the intraocular lenses

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An elegant, simple, and exact analytical solution (AS) was obtained for a large range of elementary steps with practical importance in free radical polymerization. The AS matches excellently with the numerical solution for the four cases of monomer− polymer systems studied ranging from the slowest to the fastest. It works equally well for different initiators, different initiator and monomer concentrations, presence or absence of solvent, various solvent volume fractions, and different temperatures. It also matches quite well with experimental data reported in the literature. This AS is not only in line with previous published solutions but also extends their applicability in a natural way. Overall, the conceptual correctness as well as predictive capabilities of the derived AS are established beyond doubt. This AS has the potential to be used in various practical applications such as model based process control, CFD simulations, and so forth.