An Easy Way Toward ε‐Caprolactone Macromonomers by Microwave Irradiation Using Early Lanthanide Halides as Catalysts

Poly(ε‐caprolactone) macromonomers were synthesized under microwave irradiation from commercial caprolactone, using commercial hydrated lanthanide halides as catalysts. The molecular weight of the polymers was in the range 3 000–5 000. Higher molecular weights (5 000–20 000) and lower polydispersity indices were obtained with THF adducts of the lanthanide halides as catalysts and also by applying longer reaction times or using diethylene glycol as a coupling reagent.     

Chain-extending of Hydroxytelechelic Polybutadiene: Synthesis and Characterization

Extension of hydroxytelechelic polybutadiene oligomers ( 3200 g/mol) is performed in mild conditions, in order to avoid backbone modifications, using succinic anhydride or methylenedicyclohexyl diisocyanate. The two routes present significative extension of the initial oligomers. Extension through the anhydride route, in the presence of DCC and DMAP, leads to new hydroxytelechelic oligomers ( 8000 g/mol). Extension through the diisocyanate route, catalyzed by DBTL at 65°C leads to hydroxytelechelic oligomers of higher average molecular weight ( 20000 g/mol). New materials are characterized by FTIR/¹H-NMR and changes in their Tg according to , are discussed. The influence of reaction time on the length of the macromolecular chains is also studied.     

Synthesis of hydrophobically end‐capped poly(ethylene glycol)s with UV absorbing properties

Poly(ethylene glycol)s (PEGs) with one, two or four hydrophobic end groups were prepared. Naphthyl (Nap) and phenyladamantyl (PhAd) modifiers were chosen to obtain UV absorbing PEGs. Naphthyl groups were attached to PEG ends by a one step esterification reaction, while phenyladamantyl modifiers were grafted through a tosyl intermediate.     

Characterizations of Thermoplastic Block Elastomers Based on Polybutadiene and ε -Caprolactone

A broad series of tri- and multiblock copolymers based on linear and branched oligomers of polybutadiene as central blocks and polycaprolactone (PCL) as block extremities are characterized by SEC, DSC, DMA, Dynamical Rheology and DRX. DSC analyses reveal phase separation between the two amorphous PB and PCL phases. By thermal analysis, the glass transition temperature of PCL is only detected for materials containing at least 80% w/w of PCL. This is attributed to the small length of the polyester blocks for copolymers containing less than 80% w/w of PCL. The increase of fusion heat with increasing PCL content in the copolymers is correlated to the greater ability of PCL chains to rearrange as HTPB amount decrease in the material. Regarding the evolution of the melting temperature of the various copolymers, the characterization by DMA and dynamical rheology confirms the behaviour observed by DSC. Mechanical and rheological properties (i.e., storage modulus and complex viscosities) were studied and reveal that the behavior of the copolymers depends on both the rate of PCL chains and on the nature of the elastomeric block.     

Comparison of various methods of grafting of modified-PEG onto maghemite nanoparticles in aqueous medium including synthesis by microwave refluxing

Three methods in the synthesis of functionalized maghemite nanoparticles in aqueous medium by grafting triethoxysilane monomethylene-PEG (Si-mPEG) onto maghemite nanoparticles were compared including synthesis by microwave refluxing which is an original device designed by our research team. The maghemite nanoparticles were characterized by zeta potential measurement, X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). The spinel structure of maghemite nanoparticles was determined and successful grafting of m-PEG was evidenced. Thermogravimetric analysis (TGA) reveals that microwave heating tends to improve the grafting rate compared to conventional heating.     

Designing Medical Devices Based on Silicon Polymeric Material with Controlled Release of Local Anesthetics

The drug delivery systems that are the object of this article take the form of a polymer matrix made of silicone containing a drug. These devices can be used as patches for local dermal applications releasing the drug in a controlled manner. The model active agent, lidocaine hydrochloride was chosen from the range of local anesthetics. When the drug is restricted to the surface, it is released more rapidly than when it is allowed to spread evenly throughout the silicon structure. When hydrophilic polymers such as PVA and HEC are mixed in with the lidocaine hydrochloride and deposited on the surface of the polymer matrix, we observed that the burst effect was eliminated without modifying the overall quantity of lidocaine hydrochloride released.     

Microwave-assisted one-step hydrothermal synthesis of pure iron oxide nanoparticles: magnetite, maghemite and hematite

A simple, rapid, one-step synthesis way of pure iron oxide nanoparticles: magnetite (Fe₃O₄), maghemite (γ-Fe₂O₃) and hematite (α-Fe₂O₃) was investigated. Nanoparticles were prepared by microwave synthesis, from ethanol/water solutions of chloride salts of iron (FeCl₂ and FeCl₃) in the presence of sodium hydroxide NaOH. X-ray powder diffraction (XRD), Transmission Electron Microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to characterize these nanoparticles.     

New approach for synthesis of poly(ethylglyoxylate) using Maghnite-H+, an Algerian proton exchanged montmorillonite clay,as an eco-catalyst

In this works, we have explored a new method for a green synthesis of poly(ethylglyoxylate) (PEtG). This method consists on using a montmorillonite clay called “Maghnite-H⁺” as an eco-catalyst to replace triethylamine which is toxic. Cationic polymerization experiments are performed in bulk conditions at three temperatures (?40°C, 25°C, 80°C) and in THF solutions at room temperature (25°C). At 25°C, an optimum ratio of 5 wt% of catalyst leads to molar masses up to 22000 g/mol in THF solutions. Polymerizations in bulk conditions lead to slightly lower masses than experiments conducted in THF solutions. However, bulk polymerization of ethyleglyoxylate remains a preferable method in order to avoid the use of a solvent and therefore to stay in the context of green chemistry. The structure of obtained polymers are characterized and confirmed by ¹H and ¹³C NMR. Thermogravimetric Analysis (TGA) shows an enhanced thermal stability for end-capped PEtG compared to non-terminated PEtG. The best conversion rate (92%) is observed in bulk conditions at 25°C for a reaction time of 48h. An activation energy could be calculated from bulk experiments (Ea = 6.9 kJ/mol). An interesting advantage of Maghnite-H⁺ is an easy recoverage by a simple filtration from the polymer solution.     

In Vitro Release of Local Anaesthetic and Anti-Inflammatory Drugs from Crosslinked Collagen Based Device

The drug delivery systems that are the object of this article take the form of a hydrophilic matrix (collagen or crosslinked collagen) containing a drug. These devices can be used as The model active agents, were chosen from the range of local anaesthetics (lidocaine hydrochloride), anti-inflammatory (diclofenac sodium salt) and antioxydant (caffeic acid). Whatever the drug affinity for water, in the first time of the experiments, the release appears to be systematically delayed when the matrix is crosslinked. For lidocaine hydrochloride based systems, as the amount of drug increases in the matrix, the high gap concentration between the matrix and the buffer solution promote the diffusion and a Fickian behavior is observed on the release curves. Depending on the chemical nature of the drug and its solubility, several interactions between the drug and the collagen matrix can be considered. A new drug delivery system containing caffeic acid as the anti-inflammatory and antioxydant molecule could be tested. This new system was able to release 95% of the drug in 5 h and the global release rate depends on the initial drug concentration in the device.     

Lanthanides benzimidinates: initiators or real catalysts for the ε‐caprolactone polymerization

Lanthanides (samarium and ytterbium) tris and monobenzimidinates are efficient for the polymerization of ε‐caprolactone, the systems remaining active after consumption of the monomer. Nevertheless it is not a living polymerization because the benzimidinates are recovered. Evidence for support of the proposed catalytic cycle was obtained by NMR studies.