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The biocompatibility, tunable degradability and broad functionalities of polyphosphoesters and their potential for biomedical applications have stimulated a renewed interest from Chemistry, Medicinal Chemistry and Polymer Sciences. Commercial applications of polyphosphoesters as biomaterials are still hampered because of the time and resource-intensive sourcing of their corresponding monomers, in addition to the corrosive and sensitive nature of their intermediates and by-products. Here, we present a groundbreaking challenge for sourcing the corresponding cyclic phosphate monomers by a different approach. This approach relies on the use of continuous flow technologies to intensify the end-to-end preparation of cyclic phosphate monomers with a semi-continuous modular flow platform. The applied flow technology mitigates both safety and instability issues related to the more classical production of cyclic phosphate monomers. The first flow module allows safe synthesis of a library of cyclic chlorophosphite building blocks and features in-line P-31 NMR real-time monitoring. After optimization on the microfluidic scale, this first module is successfully transposed toward mesofluidic scale with a daily throughput of 1.88 kg. Downstream of the first module, a second module is present, allowing the quantitative conversion of cyclic chlorophosphites with molecular oxygen toward chlorophosphate derivatives within seconds. The two modules are concatenable with a downstream semi-batch quench of intermediate chlorophosphate with alcohols, hence affording the corresponding cyclic phosphate monomers. Such a continuous flow setup provides considerable unprecedented advantages to safely and efficiently synthesize a library of versatile high value-added cyclic phosphate monomers at large scale. These freshly produced monomers can be successfully (co)polymerized, using either batch or flow protocols, into well-defined polyphosphoesters with assessed thermal properties and cytotoxicity.

Solid-state lithium batteries are considered one of the most promising battery systems due to their high volumetric energy density and safety. Poly(ethylene oxide) (PEO) is the most commonly used solid polymer electrolyte in solid-state batteries. In this article, we introduce new polyphosphoester polymer electrolytes, which show improved flame retardant properties in comparison with PEO. For this purpose, new polyphosphoester copolymers were synthesized, including phosphoester, poly(ethylene glycol) (PEG) and UV cross-linkable vinyl units. Solid polymer electrolyte films based on polyphosphoester copolymers and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) were prepared by curing under UV-light. The crystallinity present in the copolymers due to the PEG segment decreases with the amount of salt in the electrolyte, as seen by DSC. Solid polymer electrolytes based on polyphosphoester copolymers show ionic conductivity values as high as 2 × 10−4 S cm−1 at 70 °C. FTIR analysis showed that lithium cations complexed with phosphoester groups provoked an increase in the lithium transference number to 0.26 as compared to that of PEO 0.17. Pyrolysis flow combustion calorimetry (PCFC) or micro-calorimetry results demonstrated the improved flame retardancy of the polyphosphoesters in comparison to a reference PEO based polymer electrolyte. The selected polyphosphoester solid electrolyte was investigated in a solid-state lithium cell Li0/polymer electrolyte/LFP battery showing a specific capacity retention close to 80% and coulombic efficiency greater than 98% over 100 cycles at 70 °C.

The synthesis and properties of hybrid poly(ε-caprolactone) (PCL)–poly(ethylene oxide) (PEO) covalent adaptable networks have been investigated.

Les modules de puissance sont une des parties elementaires utilisees en electronique pour realiser des circuits de conversion d'energie, comme ceux d'un onduleur. Un module de puissance est constitue des elements suivants : des puces semi-conductrices, un substrat ceramique metallise, une semelle, des brasures, des elements de connexion internes, des terminaux electriques et un encapsulant. Ces constituants ont des proprietes electriques, thermiques et mecaniques differentes, susceptibles d'affecter les performances globales du module de puissance. Cet article dresse un etat de l'art sur les diverses fonctions d'un module de puissance et presente les technologies actuelles pour les mettre en œuvre. Les aspects « densite de puissance elevee » et « fonctionnement haute temperature » - au-dela de 200 °C - sont plus particulierement developpes.

Introduction: We hypothesised that the active targeting of αvβ3 integrin overexpressed in neoangiogenic blood vessels and glioblastoma (GBM) cells combined with magnetic targeting of paclitaxel- and SPIO-loaded PLGA-based nanoparticles could improve accumulation of nanoparticles in the tumour and therefore improve the treatment of GBM. Methods: PTX/SPIO PLGA nanoparticles with or without RGD-grafting were characterised. Their in vitro cellular uptake and cytotoxicity was evaluated by fluorospectroscopy and MTT assay. In vivo safety and anti-tumour efficacy of different targeting strategies were evaluated in orthotopic U87MG tumour model over multiple intravenous injections. Results: The nanoparticles of 250 nm were negatively charged. RGD targeted nanoparticles showed a specific and higher cellular uptake than untargeted nanoparticles by activated U87MG and HUVEC cells. In vitro IC50 of PTX after 48 h was ∼1 ng/mL for all the PTX-loaded nanoparticles. The median survival time of the mice treated with magnetic targeted nanoparticles was higher than the control (saline) mice or mice treated with other evaluated strategies. The 6 doses of PTX did not induce any detectable toxic effects on liver, kidney and heart when compared to Taxol. Conclusion: The magnetic targeting strategy resulted in a better therapeutic effect than the other targeting strategies (passive, active).

Antimicrobial peptide loaded poly(2-hydroxyethyl methacrylate) particles were synthesized in supercritical carbon dioxide via one-pot free-radical dispersion polymerisation of 2-hydroxyethyl methacrylate and a cross-linker. Discrete particles with a well-defined spherical morphology and a diameter as low as 450 nm have been obtained in mild conditions. The encapsulation and release of the peptide were confirmed by antimicrobial tests that demonstrated for the first time a sustained release of the peptide from poly(2-hydroxyethyl methacrylate) microgels prepared by one-pot dispersion polymerization in supercritical carbon dioxide and then dispersed in water.

In the recent decades, biodegradable and biocompatible polyphosphoesters (PPEs) have gained wide attention in the biomedical field as relevant substitutes for conventional aliphatic polyesters. These amorphous materials of low glass transition temperature offer promise for the design of soft scaffolds for tissue engineering. Advantageously, the easy variation of the nature of the lateral pendant groups of PPEs allows the insertion of pendent unsaturations valuable for their further cross-linking. In addition, varying the length of the pendent alkyl chains allows tuning their hydrophilicity. The present work aims at synthesizing PPE networks of well-defined hydrophilicity and mechanical properties. More precisely, we aimed at preparing degradable materials exhibiting identical hydrophilicity but different mechanical properties and vice versa. For that purpose, PPE copolymers were synthesized by ring-opening copolymerization of cyclic phosphate monomers bearing different pendent groups (e.g., methyl, butenyl, and butyl). After UV irradiation, a stable and well-defined cross-linked material is obtained with the mechanical property of the corresponding polymer films controlled by the composition of the starting PPE copolymer. The results demonstrate that cross-linking density could be correlated with the mechanical properties, swelling behavior, and degradation rate of the polymers network. The polymers were compatible to human skin fibroblast cells and did not exhibit significant cytotoxicity up to 0.5 mg mL-1. In addition, degradation products appeared nontoxic to skin fibroblast cells and showed their potential as promising scaffolds for tissue engineering.

Polymer micelles have emerged as promising carriers for controlled release applications, however, several limitations of micelle-based drug delivery have also been reported. To address these issues, we have synthesized a functional biodegradable and cytocompatible block copolymer based on methoxypoly(ethyleneglycol)-b-poly(ε-caprolactone-co-α-azido-ε-caprolactone) (mPEG-b-poly(εCL-co-αN3εCL)) as a precursor of reduction sensitive core-crosslinked micelles. The synthesized polymer was formulated as micelles using a dialysis method and loaded with the anti-inflammatory and anti-cancer drug methotrexate (MTX). The micellar cores were subsequently crosslinked at their pendant azides by a redox-responsive bis(alkyne). The size distributions and morphology of the polymer micelles were assessed using dynamic light scattering (DLS) and transmission electron microscopy, and drug release assays were performed under simplified (serum free) physiological and reductive conditions. Cellular uptake studies in human breast cancer cells were performed using Oregon-green loaded core-crosslinked micelles. The MTX-loaded core-crosslinked micelles were assessed for their effects on metabolic activity in human breast cancer (MCF-7) cells by evaluating the reduction of the dye MTT 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide. The apoptosis inducing potential of MTX-loaded core-crosslinked micelles was analysed using Hoechst/propidium iodide (PI) and annexin-V/PI assays. The data from these experiments indicated that drug release from these cross-linked micelles can be controlled and that the redox-responsive micelles are more effective carriers for MTX than non-crosslinked analogues and the free drug in the cell-lines tested.

Chemical crosslinking is an efficient tool to improve or impart new properties to conventional polymers. Especially, crosslinking imparts remarkable shape–memory properties to poly-e-caprolactone (PCL) materials. Nevertheless, the processing of networks is often tricky due to infusibility and insolubility of cross-linked chains. Therefore, the synthesis of PCL networks including thermo-reversible crosslinks based on (retro)-Diels-Alder (DA) reaction were developed to allow preserving the melt-processing while keeping the required mechanical properties below the melting point. This paper aims at studying in depth, such thermo-dependent network formation and stability. Besides conventional swelling experiments, Raman spectroscopy was revealed as a powerful tool to follow the formation of the DA adduct during the crosslinking. In combination with rheological measurements, we were able to determine the most appropriate temperatures to form the network (DA crosslinking) and to process it (retro-DA reaction) without degradation of the material.

Photochemically cross-linked shape-memory polymer (SMP) materials have been achieved by functionalizing chain-ends of star-shaped poly(ϵ-caprolactone) (PCL) with 7-hydroxypropoxy-4-methylcoumarin followed by photodimerization of these end-groups. The kinetics of the network formation in function of the photosensitizer concentration has been studied by swelling experiments and rheology. Thanks to the design of a dedicated homemade mold, highly reproducible irradiation conditions have been achieved allowing to study the network formation and properties, especially the shape-memory properties, in relation to the coumarin dimerization degree as determined by Raman spectroscopy. In optimized conditions, PCL-based SMP materials exhibiting high fixity and recovery have been achieved in remarkably short irradiation time, typically 5 min. In addition, the precise control of the network cross-link density with the irradiation time, so as the high stability of the formed networks toward temperature variations was also demonstrated allowing the fine-tuning of the network properties by the irradiation process. Finally, the reversible character of the coumarin dimerization under light irradiation of appropriate wavelength has been quantified by Raman spectroscopy. The dimer photocleavage allows the photoreconfiguration of the networks offering the ability to modify the "permanent" shape of the SMP material, while preserving the excellent shape-memory properties.

Glioblastoma is the most frequent and aggressive primary malignant tumor of the central nervous system with a gloomy prognosis. Platinum derivatives and one among them, cisplatin, exhibited promising results when locally administered into the brain of glioblastoma bearing rats. Nanovectorization of anticancer agents through polymeric nanoparticles may even promote drug accumulation within cells, thus concentrating the drug efficiently at its target. Anchorage of gadolinium complexes on the corona of such smart drug delivery systems could further allow magnetic resonance imaging (MRI) monitoring of the nanoplatform biodistribution in the damaged parenchyma and its therapeutic benefit. For this purpose, a biocompatible amphiphilic triblock copolymer, made of degradable polyester and polycarbonate and bioeliminable polyethylene oxide (PEO), was synthesized by successive ring-opening polymerizations. After micellization in water, gadolinium complexes were grafted onto the PEO micelle corona and the carboxylate functions, located at the surface of the micelle's core, were able to cross-link with Pt(ii) complexes. A macromolecular prodrug was therefore recovered in which more than one third of the carboxylate functions were linked to a platinum atom. By this strategy, stable cisplatin cross-linked nanoparticles were formulated with a mean size in the range of 100.63 ± 12.04 nm consistent with biological investigations. Relaxometry measurements both in water and in plasma at 7 T, 25 °C, confirmed the intrinsic potential of these hybrid nanoparticles as alternative MRI contrast agents with a substantial increase in the r2/r1 ratio by a factor of 3.3 and 2.7, respectively, compared to the conventional low molar mass Gd-DTPA. As a result, their infusion within the striatum of glioblastoma-bearing mice resulted in a hypersignal on T2-weighted MR images that persisted over time. Ultimately, the formulated prodrug exhibited up to 50-fold increased accumulation in human glioblastoma cell lines and up to 32-fold enhanced subsequent Pt-DNA adduct formation in comparison with free cisplatin, thus supporting the potential of this innovative bimodal tool for further applications.

Sulindac loaded poly(HEMA) cross-linked microparticles were synthesized via one-pot free-radical dispersion polymerisation in supercritical carbon dioxide (scCO2) in presence of photocleavable diblock stabilisers based on polyethylene oxide (PEO) and poly(heptadecafluorodecyl acrylate) (PFDA) bearing a o-nitrobenzyl photosensitive junction (hv) (PEO-hv-PFDA), and ethylene glycol dimethacrylate (EGDMA) as cross-linker. Poly(HEMA) cross-linked microparticles either empty or sulindac loaded were obtained with well-defined spherical morphology with the sizes between 250 and 350 nm. Additionally, upon UV-photolysis the stabiliser on the surface was cleaved which permits to microparticles to be redispersed in water leading to water swollen microgels about 2.1–3.6 µm. Moreover, the release behaviour from obtained microgels indicated the sustained release of sulindac over 10 days. Besides, the surface modification after UV-photolysis was studied and proved that the particles can be functionalised with further chemistries.

Poly(ethylene oxide)-b-polyphosphoester amphiphilic block copolymers are known to self-assemble into polymer micelles when dissolved in water. This work aims at reporting on the improvement of the stability of the micelles at high dilution by crosslinking the hydrophobic polyphosphoester micellar core. Typically, an unsaturated alkene side-chain was introduced onto the cyclic phosphate monomer according to a one-step reaction followed by its organocatalyzed polymerization initiated by a poly(ethylene oxide) macroinitiator. This strategy avoids the use of any organometallic compounds in order to facilitate the purification and meet the stringent requirements of biomedical applications. After self-assembly in water, the micelles were cross-linked by simple UV irradiation. These cross-linked micelles have then been loaded with doxorubicin to evaluate their potential as drug nanocarriers and monitor the impact of crosslinking on the release profile.

International audience; Glioblastoma is the most frequent and aggressive primary malignant tumor of the central nervous system with a gloomy prognosis. Platinum derivatives and one among them, cisplatin, exhibited promising results when locally administered into the brain of glioblastoma bearing rats. Nanovectorization of anticancer agents through polymeric nanoparticles may even promote drug accumulation within cells, thus concentrating the drug efficiently at its target. Anchorage of gadolinium complexes on the corona of such smart drug delivery systems could further allow magnetic resonance imaging (MRI) monitoring of the nanoplat-form biodistribution in the damaged parenchyma and its therapeutic benefit. For this purpose, a biocom-patible amphiphilic triblock copolymer, made of degradable polyester and polycarbonate and bioelimin-able polyethylene oxide (PEO), was synthesized by successive ring-opening polymerizations. After micelli-zation in water, gadolinium complexes were grafted onto the PEO micelle corona and the carboxylate functions, located at the surface of the micelle's core, were able to cross-link with Pt(II) complexes. A macromolecular prodrug was therefore recovered in which more than one third of the carboxylate functions were linked to a platinum atom. By this strategy, stable cisplatin cross-linked nanoparticles were formulated with a mean size in the range of 100.63 ± 12.04 nm consistent with biological investigations. Relaxometry measurements both in water and in plasma at 7 T, 25 °C, confirmed the intrinsic potential of these hybrid nanoparticles as alternative MRI contrast agents with a substantial increase in the r 2 /r 1 ratio by a factor of 3.3 and 2.7, respectively, compared to the conventional low molar mass Gd-DTPA. As a result, their infusion within the striatum of glioblastoma-bearing mice resulted in a hypersignal on T 2-weighted MR images that persisted over time. Ultimately, the formulated prodrug exhibited up to 50-fold increased accumulation in human glioblastoma cell lines and up to 32-fold enhanced subsequent Pt-DNA adduct formation in comparison with free cisplatin, thus supporting the potential of this innovative bimodal tool for further applications.

Poly(ethylene oxide) (PEO)-b-polyphosphate copolymers made of hydrophilic PEO and hydrophobic polyphosphates are amphiphilic copolymers prone to self-assemble in water into nanoparticles. In this work, nanoparticles are obtained by the self-assembly of PEO-b-polyphosphate copolymers in water in the absence of any organic co-solvent whatever the length of the pendant alkyl chain (between 4 and 7 carbon atoms) of the polyphosphate block. Remarkably, this solvent-free process remains efficient even for the most hydrophobic polyphosphate blocks. The critical aggregation concentration (CAC) of the block copolymers was determined by pyrene probe fluorescence. Finally, the efficiency of these copolymer surfactants to decrease the air-water interface was measured by air-bubble tensiometry.

A new functional polymer micelle with high loading efficiency of a poorly soluble drug was made of biocompatible and/or biosourced compounds, i.e. cholesterol–poly(ethylene glycol)–glucosamine (Chol–PEG–GlcNH2). A synthesis strategy combining enzymatic and metal-free click chemistry was developed in order to meet the increasingly stringent requirements of biomedical applications. After the self-assembly of the Chol–PEG–GlcNH2 amphiphilic polymer in water, the presence of glucosamine at the micelle surface confers an active targeting moiety to the nanocarriers whereas protonation of the peripheral primary amine delay their aggregation. The complete characterization of this novel functional amphiphilic bioconjugate is presented as well as its aqueous solution behaviour and encapsulation efficiency using ketoconazole as a model hydrophobic drug.

In this paper, we present a small (25×25×3 mm3) power module that integrates two silicon-carbide (SiC) JFETs to form an inverter leg. This module has a “sandwich” structure, i.e. the power devices are placed between two ceramic substrates, allowing for heat extraction from both sides of the dies. All interconnects are made by silver sintering, which offers a very high temperature capability (the melting point of pure silver being 961 °C). The risk of silver migration is assessed, and we show that Parylene-HT, a dielectric material that can sustain more than 300 °C, can completely coat the module, providing adequate protection.

Local treatment using drug loaded implants allows decreasing seric concentrations of the active ingredient with the purpose of limiting side effects and reaching perfect observance. Nowadays, some diseases are already treated with implants, but generally, by subcutaneous or intra vaginal implantation. In this work, a new implant device dedicated to the intra-peritoneal cavity was developed. For this purpose, a core-membrane polymer implant was selected. We propose an original method to determine the most appropriate membrane to control the release based on the use of Franz cells. The ability of the implant to release a constant quantity of an active ingredient will be assessed by testing implants in vitro. Finally, intra peritoneal cavity and subcutaneous in vivo implantation has been achieved in order to confirm the controlled and local release of the active ingredient.

International audience; Silver sintering is a promising alternative to high melting point (HMP) solders which contain lead. Indeed, it offers better thermal and electrical properties, and can operate at higher temperature. However, silver tends to migrate in presence of electric field, oxygen (or moisture) and high temperature, causing short circuits. In this paper, we assess the extend of this issue, and we evaluate the protective effect of a thin layer of parylene. It is shown that silver migration occurs rapidly (tens to hundred of hours at 300°C), but that parylene offers a good mitigation of this issue.

National audience; Silver sintering is a promising alternative to high melting point (HMP) solders which contain lead. Indeed, it offers better thermal and electrical properties, and can operate at higher temperature. Currently, several implementations of this technique are available, based on various silver particles sizes and sintering additives. This paper presents a review of the different implementations, and gives practical details about one of them, based on silver nanoparticles. One specific aspect is highlighted: the metal finish of the DBC substrate. It has a major impact on the quality of the sintered joint: with some finishes, the adhesion is excellent (more than 50 MPa), while it is poor with some others (lower than 10 MPa).

International audience; Silicon Carbide (SiC) Junction-Field Effect Transistors (JFETs) are attractive devices for power electronics. Their high temperature capability should allow them to operate with a reduced cooling system. However, experiments described in this paper conclude to the existence of runaway conditions in which these transistors will reach destructive temperatures.

Amphiphilic biocompatible copolymers are promising materials for the elaboration of nanosystems for drug delivery applications. This paper aims at reporting on the synthesis of new functional amphiphilic copolymers based on biocompatible and bioeliminable blocks. Poly(ethylene oxide) was selected as the hydrophilic block, whereas an aliphatic polyester, i.e. poly(e-caprolactone), or a polycarbonate, i.e. poly(trimethylene carbonate), was chosen as the degradable hydrophobic block. In order to allow a post-functionalization of the micelles core, azide groups were introduced on the hydrophobic segment to provide reactivity towards functional alkyne derivatives by the copper azide–alkyne cycloaddition (CuAAC). For this purpose, a functional lactone, i.e. α-chloro-e-caprolactone, was introduced during the polymerization of the hydrophobic block before being converted into azide on the preformed copolymer. Such reactivity of the block copolymers and their self-assemblies is of prime interest for drugs or fluorescent dyes grafting, or for the crosslinking of the micelle's core. The influence of the azides distribution along the degradable block on the micelles post-functionalization ability has been studied by using alkyne bearing fluorescent dyes as models for drugs. The hydrophilicity of the dye on the micelles post-functionalization efficiency has also been investigated.

International audience; With the emergence of new power semiconductor devices, the switching speeds in power converters are increasing. The stray inductances of switching cells must therefore be minimized to limit over-voltages on transistors. One relatively new approach, called Power Chip-on-Chip (PCoC), considers the integration of power dies, one on top of the other, directly in the busbar. This allows for the reduction of the stray inductance. This paper first presents the implementation of a PCoC module using classical packaging techniques. Then a description of the different technological steps for the realization is outlined. Finally, experimental characterization results confirm the lower stray inductances offered by the PCoC package compared with the planar one.

Three-arm (A(2)B) and four-arm (A(2)B(2)) star-shaped copolymers based on biocompatible and biodegradable hydrophobic poly(epsilon-caprolactone) (PCL) (A arms) and biocompatible and bioeliminable hydrophilic poly(ethylene oxide) (PEO) (B arms) were synthesized by the coupling of an omega-azide terminated PEO chains with PCL chain bearing one (A(2)B) or two (A(2)B(2)) alkyne functions at the middle of the chain by the copper mediated azide-alkyne cycloaddition (CuAAC). The amphiphilic behavior of these different stars was confirmed by micellization experiments in water followed by dynamic light scattering and transmission electron microscopy analyses. The efficiency to stabilize PLA nanoparticles was investigated in function of the stars structure.

[4+2] thermoreversible Diels-Alder cycloaddition has been used to crosslink star-shaped poly(e-caprolactone) in order to produce networks based on strong carbon-carbon covalent bondings. Depending on the nature of the Diels-Alder reactants, these bonds can be thermoreversibly broken, allowing re-processing of the polymer matrix.

Star-shaped poly(ϵ-caprolactone)s are functionalized by various dienes (furan and anthracene) and a dienophile (maleimide), and the kinetics of network formation by melt-blending is compared for both Diels–Alder adducts. When curing at 60 °C, the anthracene–maleimide network forms more rapidly and gives rise to a more crosslinked material than with the furan–maleimide adduct. Shape-memory properties of the networks are compared in terms of Diels–Alder adduct stability. Both materials exhibit excellent fixity and recovery ratios, but the relatively low retro Diels–Alder temperature of the furan–maleimide adduct perturbs the mechanical stability of the network during cyclic tensile testing between 0 and 60 °C, whereas the anthracene–maleimide adduct is shown to be stable up to 150 °C.

The intraperitoneal biocompatibility of PDMS, polyHEMA and pEVA was investigated in rats, rabbits and rhesus monkeys. No inflammation was evidenced by hematological analyses and measurement of inflammatory markers throughout the experiment and by post-mortem examination of the pelvic cavity. After 3 or 6 months, histological analysis revealed fibrous tissue encapsulating PDMS and PEVA implants in all species and polyHEMA implants in rabbits and monkeys. Calcium deposits were observed inside polyHEMA implants. The intraperitoneal biocompatibility of all 3 polymers makes them suitable for the design of drug delivery systems, which may be of great interest for pathologies confined to the pelvic cavity.

This article reports on the synthesis of a new pH-sensitive amphiphilic A2B mikto-arm star-shaped aliphatic copolyester [with A = poly(e-caprolactone) and B = tertiary amine-bearing poly(e-caprolactone)] with two hydrophobic arms and one hydrophilic arm when protonated at pH = 5.5. First, the ring-opening polymerization of e-caprolactone (eCL) was initiated by an aliphatic diol substituted by an alkyne. The copper(I) catalyzed azide-alkyne cycloaddition (CuAAC) was use to convert the alkyne into a hydroxyl group prone to initiate the ring-opening copolymerization of γ-bromo-e-caprolactone (γBreCL) and eCL. After the substitution of the bromide atoms into azide functions, the N,N-dimethylprop-2-yn-1-amine was grafted onto the azide bearing PCL arm by CuAAC, with the purpose to make the B arm hydrophilic at low pH. The precursors of the A2B copolymers were characterized by 1H NMR, SEC, and MALDI-TOF. As expected, the A2B copolyester was soluble into water at pH = 5. The formation of polymersomes in water at pH 5 was assessed by DLS and TEM analyses. The effects of the architecture and the molecular weight of the A2B copolymers on the formation of polymersomes were investigated. Moreover, the versatility of our approach was demonstrated by the synthesis of an AB2 star-shaped copolyester. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

This paper describes the synthesis of a novel amphiphilic AB 2 triarm star-shaped copolymer with A = non-toxic and biocompatible hydrophilic poly(ethylene oxide) (PEO) and B = biodegradable and hydrophobic poly(e-caprolactone) (PCL). A series of AB 2 triarm star-shaped copolymers with different molecular-weights for the PCL block were successfully synthesized by a three-step procedure. α-Methoxy-ω-epoxy-poly(ethylene oxide) (PEO-epoxide) was first synthesized by the nucleophilic substitution of α-methoxy-ω-hydroxy-poly(ethylene oxide) (MPEO) on epichlorohydrin. In a second step, the α-methoxy-ω,ω′-dihydroxy-poly(ethylene oxide) (PEO(OH) 2 ) macroinitiator was prepared by the selective hydrolysis of the ω-epoxy end-group of the PEO-epoxide chain. Finally, PEO(OH) 2 was used as a macroinitiator for the ring-opening polymerization (ROP) of e-caprolactone (eCL) catalyzed by tin octoaote (Sn(Oct) 2 ). PEO-epoxide, PEO(OH) 2 and the AB 2 triarm star-shaped copolymers were assessed by 1 H NMR spectroscopy, size exclusion chromatography (SEC) and MALDI-TOF. The behavior of the AB 2 triarm star-shaped copolymer in aqueous solution was studied by dynamic light scattering (DLS) and transmission electron microscopy (TEM).

Biodegradability makes aliphatic polyesters valuable candidates for biomaterials and environmentally friendly thermoplastics. Nevertheless, their chemical modification, which is mandatory for a series of potential applications, is usually a problem because it must be carried out under very mild conditions in order to prevent degradation by hydrolysis and/or transesterification from occurring. In this review, the copper(I)-catalyzed azide-alkyne cycloaddition, which is a click reaction, is shown to be very efficient to bypass these problems and to tailor the macromolecular architecture and functionality of those polyesters without facing undesired degradation reactions.

A straightforward strategy is proposed to impart antimicrobial properties to biodegradable poly(oxepan-2-one) (poly(ɛ-caprolactone) or PCL), which is based on the grafting of pendant ammonium salts by “click” chemistry. First, statistical copolymerization of 3-chlorooxepan-2-one (α-chloro-ɛ-caprolactone or αClɛCL) with oxepan-2-one (ɛ-caprolactone or ɛCL) was initiated by 2,2-dibutyl-2-stanna-1,3-dioxepane (DSDOP). In a second step, pendant chlorides were converted into azides by reaction with sodium azide (NaN3). Finally, quaternary ammonium containing alkynes were quantitatively added to the pendant azide groups of PCL by the copper-catalyzed Huisgen's 1,3-dipolar cycloaddition, which is a typical “click” reaction. An alternative two-step strategy based on the cycloaddition of the amine containing alkyne onto the pendant azides, followed by quaternization turned out to be less efficient. The antimicrobial activity was analyzed by the “shaking flask method” in the presence of Escherichia coli (E. coli).

Copper-mediated azide–alkyne Huisgen's 1,3-dipolar cycloaddition is a “click” reaction that was successfully used to prepare pH-responsive, amphiphilic and biodegradable networks. Indeed, this reaction proved to be very efficient in the “one pot” grafting of amino alkyne onto azide containing poly(ɛ-caprolactone) and the cross-linking of these chains by α,ω-dialkynyl poly(ethylene oxide). The pH-controlled release of guests hosted during the cross-linking step was illustrated with an entrapped model dye.

A tadpole shaped poly(e-caprolactone) (PCL; Mn = 24 500) was made amphiphilic by grafting the two PCL tails with PEO. In the first step, a macrocyclic PCL was synthesized by ring-opening polymeriza...

A straightforward strategy is proposed for the derivatization of poly(e-caprolactone) (PCL). First, statistical copolymerization of α-chloro-e-caprolactone (αCleCL) with e-caprolactone (eCL) was initiated by 2,2-dibutyl-2-stanna-1,3-dioxepane (DSDOP). In a second step, pendent chlorides were converted into azides by reaction with sodium azide. Finally, duly substituted terminal alkynes were reacted with pendent azides by copper-catalyzed Huisgen's 1,3-dipolar cycloaddition, thus a “click” reaction. According to this strategy, pendent hydroxyl and acrylate groups and atom transfer radical polymerization (ATRP) initiators were successfully attached to PCL. Similarly, amphiphilic graft copolymers were prepared by cycloaddition of an alkyne end-capped poly(ethylene oxide) (PEO) onto the azide substituents of the copolyester. The dependence of the grafting yield on the experimental conditions of the “click” reaction, i.e., temperature, solvent, and catalyst, was investigated. This strategy is very versatile be...

International audience; Silver sintering is an attractive alternative to soldering in power electronics, as it offers higher electrical and thermal performance. Furthermore, sintered attaches can operate at a higher temperature. In this paper, we investigate the use of silver sintering for the bonding of passive components, and for the manufacturing of so-called 3D-modules. It is shown that this technique is well suited, as it makes it possible to operate at very high temperature (up to 310 °C demonstrated), and as it simplifies the assembly process (several identical sintering steps can be performed successively without problem).

In previous works, poly(D,L-lactide-co-ɛCL-poly(ethylene glycol) (poly(D,L-La-co-αPEGɛCL) amphiphilic graft-copolymers were successfully synthesized according to a copper azide-alkyne cycloaddition (CuAAC) strategy. This paper aims at reporting on the behavior of this amphiphilic copolymer in water, which was not studied in the previous paper. Moreover, the ability of the copolymer to stabilize a PLA nanoparticles aqueous suspension is presented. For this purpose, dynamic light scattering (DLS) and transmission electron microscopy (TEM) are proposed to characterize the nanoparticles in solution. Otherwise, the strategy developed for the synthesis of the amphiphilic copolymers was adapted and extended to the synthesis of PLA-based degradable hydrogel, potentially applicable as drug-loaded degradable polymer implant.

Recent progress in the synthesis of aliphatic polyesters, substituted by pendent functional groups, has been reviewed. Two main strategies have to be distinguished. The first route consists of the ring-opening polymerization of e-caprolactone substituted by various functional groups, protected if needed, in α- or γ-position. In a second strategy, the functional groups are grafted onto preformed polyesters chains in α-position of the carbonyl groups. α-chloro-e-caprolactone is quite an interesting monomer because, after polymerization, the activated chloride can be easily derivatized by atom transfer radical addition and click chemistry, respectively. Similarly, γ-acrylic-e-caprolactone is precursor of (co)polyesters well-suited to derivatization of the pendent double bonds by Michael addition.

This paper aims at reporting on the synthesis of a heterograft copolymer by combining the "grafting onto" process based on atom transfer radical addition (ATRA) and the "grafting from" process by atom transfer radical polymerization (ATRP). The statistical copolymerization of s-caprolactone (eCL) and α-chloro-e-caprolactone (αCleCL) was initiated by 2,2-dibutyl-2-stanna-1,3-dioxepane (DSDOP), followed by ATRA of parts of the chlorinated units of poly(αCleCL-co-eCL) on the terminal double bond of α-MeO,ω-CH 2 =CH-CH 2 -CO 2 -poly(ethylene oxide) (PEO). The amphiphilic poly(eCL-g-EO) graft copolymer collected at this stage forms micelles as supported by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The unreacted pendant chloro groups of poly(eCL-g-EO) were used to initiate the ATRP of styrene with formation of copolymer with two populations of randomly distributed grafts, that is PEO and polystyrene.

A straightforward strategy is proposed for grafting hydroxyl, carboxylic acid and epoxide groups along poly(e-caprolactone) chains. Statistical copolymerization of e-caprolactone (eCL) with α-chloro-e-caprolactone (αCleCL) has been initiated by 2,2-dibutyl-2-stanna-1,3-dioxepane (DSDOP), followed by the atom transfer radical addition (ATRA) of but-3-en-1-ol, vinylacetic acid and 1,2-epoxyhex-5-ene, respectively, onto the α-chloro units of a poly(αCleCL-co-eCL) copolymer. αCleCL is easily prepared by the Baeyer–Villiger oxidation of 2-chlorocyclohexanone. The influence of the experimental conditions, i.e. temperature, solvent, catalyst, on the grafting yield has been discussed. Because ATRA is tolerant of the investigated functional groups, no protection/deprotection reaction is required, which is a major advantage of the method.

A highly versatile strategy was implemented in order to attach a range of polymer grafts and functional groups along the backbone of poly(e-caprolactone). α-Chloro-e-caprolactone (αCleCL) was first prepared by the Baeyer−Villiger oxidation of α-chlorocyclohexanone. This monomer (αCleCL) was then copolymerized with e-caprolactone in the presence of 2,2-dibutyl-2-stanna-1,3-dioxepane. Finally, the pendant activated chlorides of the copolymer were used to initiate (i) the “grafting from” of poly(methyl methacrylate) by atom transfer radical polymerization and (ii) the grafting of benzoate groups by atom transfer radical addition of 3-butenyl benzoate.

International audience; This paper presents a so-called "3D power packaging structure", in which silicon-carbide power devices are placed between two ceramic-metal substrates (DBC). This allows for more efficient cooling of the transistors (double side cooling), better electrical performance (lower resistance and inductance), and higher level of integration. The paper presents the manufacturing steps required to produce and assemble the different parts of the module: The substrates are etched with a high-resolution, two step process which exceeds the common design rules. The module is assembled using silver sintering. A new approach is used for the encapsulation of this intricate structure: parylene HT.Some of these results were published in the IMAPS HiTEC conference in may 2014. For this presentation, we will focus on new results: the electrical characterization (static and dynamic) of the power module. A half-bridge module, using two SiC JFET transistors is used for these tests.

International audience; With the emergence of new power semiconductor devices, the switching speeds in power converters are increasing. The stray inductances of switching cells must therefore be minimized to limit the over-voltages on transistors. One relatively new approach, called Power Chip-on-Chip (PCo), considers the integration of power dies, one on top of the other directly in the busbar. This allows for the reduction of the stray inductance. This paper first presents the implementation of a PCoC module using classical packaging techniques. Then a description of the different technological steps for the realization is outlined. Finally, experimental characterizations show the interest of the proposed PCoC module compared with planar ones.

International audience; The precision synthesis of poly(ionic liquid)s (PILs) in water is achieved for the first time by the cobalt-mediated radical polymerization (CMRP) of N-vinyl-3-alkylimidazolium-type monomers following two distinct protocols. The first involves the CMRP of various 1-vinyl-3-alkylimidazolium bromides conducted in water in the presence of an alkyl cobalt(III) complex acting as a monocomponent initiator and mediating agent. Excellent control over molar mass and dispersity is achieved at 30 degrees C. Polymerizations are complete in a few hours, and PIL chain-end fidelity is demonstrated up to high monomer conversions. The second route uses the commercially available bis(acetylacetonato)cobalt(II) (Co(acac)2) in conjunction with a simple hydroperoxide initiator (tertbutyl hydroperoxide) at 30, 40, and 50 degrees C in water, facilitating the scaling-up of the technology. Both routes prove robust and straightforward, opening new perspectives onto the tailored synthesis of PILs under mild experimental conditions in water.

This study aims at developing chitosan-based nanoparticles suitable for an intravenous administration of small interfering RNA (siRNA) able to achieve (i) high gene silencing without cytotoxicity and (ii) stability in biological media including blood. Therefore, the influence of chitosan/tripolyphosphate ratio, chitosan physicochemical properties, PEGylation of chitosan as well as the addition of an endosomal disrupting agent and a negatively charged polymer was assessed. The gene silencing activity and cytotoxicity were evaluated on B16 melanoma cells expressing luciferase. We monitored the integrity and the size behavior of siRNA nanoparticles in human plasma using fluorescence fluctuation spectroscopy and single particle tracking respectively. The presence of PEGylated chitosan and poly(ethylene imine) was essential for high levels of gene silencing in vitro. Chitosan nanoparticles immediately released siRNA in plasma while the inclusion of hyaluronic acid and high amount of poly(ethylene glycol) in the formulation improved the stability of the particles. The developed formulations of PEGylated chitosan-based nanoparticles that achieve high gene silencing in vitro, low cytotoxicity and high stability in plasma could be promising for intravenous delivery of siRNA.

8 pages; International audience; Although they can operate at elevated junction temperature, silicon carbide power devices can in some cases fail, even at low ambient temperature. This destruction mechanism, called the thermal run-away, is described in the paper. Then, the sensitivity of normally-on SiC JFETs (SiCED) to this mechanism is evaluated using a model based on experimental measurements performed over a wide temperature range (from -50°C to 300°C). It is shown that above a certain current level, run-away can occur. An experimental test bench is used to validate the modelling and explore the safe-operating area of these devices. The measurements confirm the sensitivity of the device to thermal run-away. Mitigation techniques are discussed.

A chemically cross-linked but remarkably (re)processable shape-memory polymer (SMP) is designed by cross-linking poly(ε-caprolactone) (PCL) stars via the efficient triazolinedione click chemistry, based on the very fast and reversible Alder-ene reaction of 1,2,4-triazoline-3,5-dione (TAD) with indole compounds. Typically, a six-arm star-shaped PCL functionalized by indole moieties at the chain ends is melt-blended with a bisfunctional TAD, directly resulting in a cross-linked PCL-based SMP without the need of post-curing treatment. As demonstrated by the stress relaxation measurement, the labile character of the TAD-indole adducts under stress allows for the solid-state plasticity reprocessing of the permanent shape at will by compression molding of the raw cross-linked material, while keeping excellent shape-memory properties.

The aim of this study was to develop tocol derivatives of chitosan able (i) to self-assemble in the gastrointestinal tract and (ii) to enhance the solubility of poorly soluble drugs. Among the derivatives synthesized, tocopherol succinate glycol chitosan (GC-TOS) conjugates spontaneously formed micelles in aqueous solution with a critical micelle concentration of 2 μg mL(-1). AFM and TEM analysis showed that spherical micelles were formed. The GC-TOS increased water solubility of 2 model class II drugs. GC-TOS loading efficiency was 2.4% (w/w) for ketoconazole and 0.14% (w/w) for itraconazole, respectively. GC-TOS was non-cytotoxic at concentrations up to 10 mg mL(-1). A 3.4-fold increase of the apparent permeation coefficient of ketoconazole across a Caco-2 cell monolayer was demonstrated. Tocol polymer conjugates may be promising vehicles for the oral delivery of poorly soluble drugs.