Research in polymer chemistry is developed by the CERM team of CESAM research unit. See below for an overview or here for more detailed information.
We are active in the development of Cobalt and Nitroxide-Mediated Radical Polymerization systems (CMRP and NMP) using organometallic and organic compounds as controlling agents, respectively. We also master other CRP tools including Atom Transfer Radical Polymerization (ATRP) and Radical Addition Fragmentation chain Transfer (RAFT).
This technique allows the efficient synthesis of polymers with high and predetermined molar mass and narrow molar mass distribution under appropriate conditions. ROP is implemented to make available various architectures such as combs, stars, dendrimers, networks. ROP is carried out by a diversity of processes involving different propagating species such as anions, coordination complexes, cations, radicals, organic catalysts, enzymes. It is also remarkable that many families of cyclic monomers can be polymerized by ring-opening, making available a wide range of polymers with tailored properties. In particular, we have a lot of expertise in the polymerization of lactones, the synthesis of poly(ethylene oxide) (PEO) and ROP of cyclic phosphates and lactams.
Electrografting of acrylic monomers offers the unique opportunity to impart permanent functionality/reactivity to the surface of (semi)-conducting materials. The simple polarization of the substrate, e.g. steel, in appropriate conditions, results in the formation of a polyacrylate thin film strongly anchored to its surface. This polymerization method plays also an important role in the field of conjugated polymers often integrated as thin films in electronic devices.
The modification of the chemical structure of polymers by the grafting of functional groups along chains is a very efficient tool allowing the tailoring of many important macroscopic properties. Amongts coupling reactions, we investigate in particular the click copper-catalyzed Huisgen reaction between azides and alkyne, the metal-free thiol ene reaction and the Diels-Alder reaction between dienes and olefins. Diels-Alder reaction can be reversible or not, depending upon the chemical structure of the reactants. By this reaction, covalent bonds, stable or breakable under a stimulus such as temperature, can be made available.
Incorporation of nanoparticles in a polymer matrix is a convenient way to impart new properties to plastics. A key in the design of efficient nanocomposites lies in the mastering of the interfacial interactions, i.e., replacing strong inter-nanoparticles interactions by adapted polymer/nanoparticles interactions. We develop techniques to graft polymer by polymerization from the nanoparticle surface or innovative processes that allow polymer to be grafted onto the nanoparticles surface. We have worked with a wide variety of nanoparticles such as layered silicates, carbon nanotubes, gold or iron oxide nanoparticles. Recently, we have developed polymer grafting at the surface of graphene sheets.
We develop amphiphilic copolymers of tailor-made architecture and crosslinking strategies to create supramolecular systems (micelles, vesicles,…) that are able to respond to an external stimulus (temperature, pH,...). Responsive copolymers are also advantageously included in nanohybrid materials or nanostructured organic/inorganic frameworks imparting them additional responsiveness.
Supercritical carbon dioxide, i.e., CO2 above 31°C and 73 bars, is an interesting green alternative to traditional organic solvents because CO2 is cheap, inert, non-toxic, non-flammable and easy to remove. Monomers which are soluble in scCO2 usually polymerize into polymers which are not soluble: well-defined particles with a diameter between 0.1 and 10 µm are obtained if an a stabilizer prevents their aggregation. Water-scCO2 emulsion polymerization is another heterogeneous process that is useful for polymerizing hydrophilic monomers. CO2 can also be used as a blowing agent to produce microcellular foams. The foaming generally occurs in batch or continuous process using high-pressure reactors or CO2 assisted extruders, respectively. The addition of nanofillers (nanoclay, carbon nanotubes, graphene,…) is commonly used to decrease the cell diameter and improve the cell density by promoting heterogeneous nucleation but also to impart fire resistance or electrical conductivity to the foam.
Nowadays, polymers are applied in fields they were not necessarily intended to be, as it is the case for biomedical applications. Indeed, biocompatible polymer implants are, among other things, a good alternative for the treatment of pathologies requiring the replacement of deficient tissues (blood vessels,…).
Typical example is synthetic intraocular lens (IOL) able to replace effectively the crystalline lens of patient suffering from cataract.
Also, biocompatible polymer implants are largely applied in the pharmaceutical field as drug carriers. Whether degradable or not, active principle containing polymer implants are able to release an adequate quantity of the active principle, limiting its amount released in the body and, at the same time, side effects. Contraceptive implants are the major part of non-degradable implants already available on the market place.