Jean Jacques Robin

Synthesis of antibacterial surfaces by plasma grafting of zinc oxide based nanocomposites onto polypropylene

Antibacterial polymer surfaces were designed using ZnO nanoparticles as a bactericide. Mineral encapsulated nanoparticles were grafted onto activated polymer surfaces through their shells. Polypropylene (PP) surfaces were treated using an innovative process coupling core-shell technology and plasma grafting, well-known techniques commonly used to obtain active surfaces for biomedical applications. First, ZnO nanoparticles were encapsulated by (co)polymers: poly(acrylic acid) (PAA) or a poly(methyl methacrylate-co-methacrylic acid) copolymer [P(MMA-MA)]. Second, PP substrates were activated using plasma treatment. Finally, plasma-treated surfaces were immersed in solutions containing the encapsulated nanoparticles dispersed in an organic solvent and allowed to graft onto it. The presence of nanoparticles on the substrates was demonstrated using Fourier-Transform Infrared Spectroscopy (FTIR) analysis, Scanning Electron Microspcopy (SEM)/Energy-Dispersive X-ray (EDX), and Atomic Force Microscopy (AFM) studies. Indeed, the ZnO-functionalized substrates exhibited an antibacterial response in Escherichia coli adhesion tests. Moreover, this study revealed that, surprisingly, native ZnO nanoparticles without any previous functionalization could be directly grafted onto polymeric surfaces through plasma activation. The antibacterial activity of the resulting sample was shown to be comparable to that of the other samples.

Grafting of poly-L-lysine dendrigrafts onto polypropylene surface using plasma activation for ATP immobilization - Nanomaterial for potential applications in biotechnology

The present work describes a new environmental friendly strategy for the development of surfaces with high amine density via the grafting of native or modified poly-L-lysine dendrigraft (DGL G3) onto plasma activated polypropylene (PP), polystyrene (PS), polyimide, and polytetrafluoroethylene (PTFE) surface. Modified DGL G3 was prepared by replacement of few peripheral amines by various functionalities. Grafting efficiency was determined by wettability measurements, IRTF, XPS, AFM, and by colorimetry using optimized Coomassie Brilliant Blue method tailored for surface analysis. It was shown that a 4-7nm DGL G3 monolayer with 4×10(14)aminecm(-)(2) was covalently grafted onto various surfaces. Immobilization of adenosine triphosphate on the DGL-g-PP material from dilute solution was studied by bioluminescence and proved the ability of the material to interact with polyanionic biological compounds: 1 ATP complex with 5 amine groups. So, this material has a potential use in diagnostic and more widely for biotechnology due to its high capacity for biomolecule immobilization.

Improvement of the interfacial compatibility between cellulose and poly(L-lactide) films by plasma-induced grafting of L-lactide: the evaluation of the adhesive properties using a peel test.

HYPOTHESIS The interfacial compatibility between hydrophilic cellulose and hydrophobic poly(L-lactide) film surfaces is dependent on the interactions and interlocking of the macromolecular chains of the uppermost layers of both polymers. Grafting or coating the cellulose surface with molecular structures similar to the lactide monomer or oligomer is expected to improve the compatibility. Therefore, it should be possible to enhance the adhesive properties. EXPERIMENTS Cellulose films were oxygen plasma treated and immersed in a L-lactide solution. The grafting was performed under various conditions (power, pressure, time). The treated cellulose and poly(L-lactide) films were hot-pressed, and the resulting bi-layer laminates were subjected to a peel test. Comparative experiments were performed with the bi-layer laminates prepared from the cellulose films coated with poly(L-lactide-graft-vinyl alcohol) copolymers. FINDINGS X-ray photoelectron spectroscopy, infra-red analyses and wettability measurements revealed that chains bearing ester groups similar to that of lactide were covalently grafted onto the cellulose. The possible grafting mechanism that was initiated by the ionic species from the surface is discussed. As a result, the peel strength to separate the cellulose and the poly(L-lactide) films increased significantly. A comparison with data in the literature highlights the formation of entanglements inside the interfacial zone showing the efficiency of the plasma treatment.

Incorporation of Organomodified Layered Silicates and Silica in Thermoplastic Elastomers in Order to Improve Tear Strength

Organomodified layered silicates and silicas have been incorporated in thermoplastic elastomers such as styrene-ethylene-butylene-styrene copolymers (SEBS) and polyurethanes (PU) in order to improve mechanical properties - especially tear strength. The organically modified layered silicates used were Cloisite® 30B, a montmorillonite modified with a ternary ammonium salt with hydroxyls as end groups and Nanofil®2 which is organically modified by long chains of hydrocarbon and benzyl groups. Sepiolite, a natural clay with fibrous morphology was also used. The silicas incorporated are Aerosil 300, hydrophilic fumed silica and Aerosil R202, hydrophobic fumed silica. nanoparticles are incorporated between 1 and 5 weight percent. A compatibilizer SEBS grafted with maleic anhydride has been incorporated in some of the formulations for a better dispersion of some of the nanoparticles. Different ways of incorporation have been investigated. For SEBS formulations, melt blends of SEBS pellets and clays have been prepared with an internal mixer and then films have been casted. For polyurethanes, solvent blending of polyols and clays were carried out in a vessel and then, compression molding of the blend with diisocyanates was made to synthesize polyurethanes. Materials have been compared on the basis of normalized tear test and sequenced tensile test. Mechanical parameters, as stabilization ratio (Mullins effect) and viscoelastic ratio, have been defined by integration of the stress-strain curves obtained. An interesting improvement of tear strength was observed for modified materials.