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International audienceThe nitroxide-mediated copolymerization of poly(ethylene glycol) methyl ether methacrylate (MePEGMA) with a small amount of acrylonitrile using an SG1-based alkoxyamine initiator was shown to be a very simple and efficient technique to synthesize graft copolymers with poly(ethylene glycol) side chains. The copolymerizations were carried out in ethanol/water solutions as environmentally friendly media. Following our observation that the rate increased with the proportion of water, a polymerization temperature as low as 71 °C could be used for a water content of 75%, which conferred great flexibility to the process. The so-formed copolymers were living, with high crossover efficiency toward block copolymers. Importantly, following a cytotoxicity study over three different cell lines that represent important mammalian cell types, these polymers were shown to be noncytotoxic even at very high doses without any other purification step than a simple precipitation. These comb-shaped PEG-based polymers may represent an ideal platform for the synthesis of PEGylating moieties for proteins and nanoparticles intended to be used in the biomedical field

International audienceWell-defined fluorescent, alpha-functional polymethacrylates with PEG side chains were readily designed by nitroxide-mediated polymerization (NMP) from N-hydroxysuccinimidyl (NHS) ester-containing alkoxyamines based on the nitroxide SG1. These polymers were obtained without any purification beyond a simple precipitation. They exhibited tunable reactivities towards nucleophiles depending on the nature of the alkoxyamine used. Copolymers derived from the commercially available SG1-based alkoxyamine led to quantitative coupling with small molecules and a neuroprotective peptide whereas partial conjugation was obtained with lysozyme, used here as a model protein. Complete conjugation to the latter was obtained from similar copolymers exhibiting a less sterically hindered NHS extremity, via appropriate alkoxyamine structure, which represents the very first example of peptide/protein PEGylation with functional polymers derived from NMP

In this study, aqueous emulsion polymerization of n-butyl acrylate is performed in batch conditions without surfactants using a poly(acrylic acid)-trithiocarbonate macro-RAFT agent to control the polymerization and to stabilize the emulsion. According to the polymerization-induced self-assembly (PISA) approach, well-defined amphiphilic PAA-b-PBA diblock copolymers form and self-assemble during synthesis to yield highly stable core-shell particles with an extremely thin hard PAA shell. For the first time, we report here the specific properties of films obtained from these particular latexes. After drying the aqueous dispersion, tough and transparent films are obtained. Although the films are not chemically cross-linked, they do not dissolve in good solvents for PBA. Moreover, they remain transparent even after immersion in water. Rheology shows that the films are both stiff and ductile, thanks to the nanostructured but very low volume fraction (less than 3 wt%) of PAA forming a percolating network in the soft PBA. Compared with conventional core-shell-based films, this approach affords for the first time a route to a thin percolating honeycomb nanostructure with a sharp and strong interface between the two phases. The versatility of the synthetic procedure opens perspectives for a large range of functional materials.

We report the synthesis of the first organo-POM with thermoresponsive properties. Our concept will provide chemists with a new tool to design POMs whose solubility is reversibly controllable through an external stimulus. POM-polymer TBA(7)[POM]-poly(N,N-diethylacrylamide) (POM-PDEAAm), was prepared by grafting PDEAAm-NH(2) (obtained by RAFT polymerization) onto the activated Dawson acyl-POM, α(2)-[P(2)W(17)O(61)SnCH(2)CH(2)C(=O)](6-). Extensive MS analysis was used to monitor the chain-functionalization steps and to confirm the formation of the hybrid. Aqueous solutions of the (NH(4))(7)[POM-PDEAAm] exhibited a LCST of 38 °C. Thus, the solubility/aggregation of the hybrid was reversibly controlled by changing the temperature. Above 38 °C, the solution became cloudy, and cleared again upon cooling. Dynamic light scattering (DLS) revealed the formation of small aggregates in the range 100 nm. We assumed that the charged POM head units prevented the formation of the larger-scattering aggregates that are usually observed for PDEAAm, and promoted the formation of micelle-like structures. The conjugate exhibited a temperature transition, which was different from that of the polymer and depended on the counterions associated with the POM. This result demonstrates the potential for merging organic (in this case, polymer) and inorganic structures to afford materials that exhibit new properties.

We demonstrate in this paper how polymerization induced self-assembly (PISA) using RAFT can be used to synthesize very asymmetric but monodisperse poly(acrylic acid)-b-poly(nbutyl acrylate) block copolymers, PAA-b-PBA, with a short PAA block and a long PBA block. In the course of the surfactant-free emulsion polymerization, core-shell particles form in water, with the short hydrophilic block located at the water-particle interface, and the long hydrophobic block constituting the particle core. Drying at room temperature creates films possessing an out of equilibrium structure, where the glassy PAA block generates a percolating network of shells. When deformed in uniaxial elongation, these films combine a high stiffness in small strains (considering the low volume fraction of PAA, of only 3 wt%), a yield stress and a significant extensibility before failure. The modulus, yield stress and extensibility can be tuned by modifying the composition of the latex serum with cations or positively charged low molar mass polymers, or by changing the copolymer composition. Of particular interest was the synthesis by PISA of particles of triblock copolymer PAA-b-PBAb-PS. The out of equilibrium structure obtained had a very interesting combination of high stiffness, extensibility and high fracture toughness.

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