The research activities of the CROPS team aim to develop synthetic methodologies mainly based on controlled radical polymerization (PRC) by nitroxides (Nitroxides Mediated Polymerization – NMP), for obtaining complex macromolecular architectures. Located at the radical chemistry / polymers interface, the studies carried out in CROPS team more particularly concern the synthesis and characterization of polymer materials with specific properties (co-polymers with nanostructured blocks, nanoparticles, polymer-biomolecule conjugates, covalent monolayer coatings, metallopolymers ,…) And finding applications in various fields such as additives, environment, health and energy or molecular electronics. Our research activities are developed along three axes described below.
Nitroxides, Controlled Radical Polymerization, Complex architecture polymers, Polymers characterization
Axis 1: New polymer synthesis methodologies based on radical chemistry concepts
In this axis, a fundamental aspect is devoted to processes based on concepts of radical chemistry with a view to applying them to the field of polymers (mechanism, kinetics, synthesis of initiators, monomers, control agent, etc.). This axis revolves around three projects to maintain a high level of innovation in the field of the synthesis of polymers with complex architecture.
Understanding and optimization of the NMP process
In this component, our objective is to continue our effort on understanding the important parameters influencing the control of controlled radical polymerization (nature of the monomer, solvent, recombination rate constant, etc.). Based on our experience in the field of NMP, our ambition is to develop a nitroxide structure capable of controlling the polymerization of monomers of styrene, acrylate and methacrylate type without distinction.
Radical photopolymerization controlled by nitroxides
Photopolymerization is a method of choice for rapidly polymerizing thin film monomers. The practical applications associated with this process are currently in full development at the industrial level with extremely rapid growth (protective varnishes, inks, paints and printing plates, holography, etc.). However, a major obstacle to the development of these systems is the lack of control over the final properties of the polymer obtained.
To overcome this problem and open up an even wider field of applications for photopolymer materials, industry needs new molecules capable of initiating the photopolymerization reaction in a controlled manner. As part of an ANR JCJC project, we have initiated a project to extrapolate the thermal polymerization mode of NMP to a photochemical mode. The results obtained are very promising but can be improved. Consequently, a significant effort of our research effort is devoted to the synthesis and the physicochemical study of new photosensitive alkoxyamines.
Radical synthesis of aliphatic polyesters
Aliphatic polyesters have the huge advantage of being biodegradable. However, the synthesis of these materials often requires the use of ionic polymerization techniques involving stringent experimental conditions. Some data in the literature show that aliphatic polyesters can be obtained by the radical route via ring opening (rROP) of cyclic acetal ketene for example. In this context, our objective aims to study in detail the polymerization by opening of radical ring in the presence of nitroxide, rROP (synthesis of new monomers, study of their radical reactivity, establishment of structure-reactivity correlations).
Axis 2: Synthesis of polymers with controlled architecture and composition
The materials that we are preparing are intended to find applications in fields which presently constitute scientific and societal challenges of great importance. This voluntary approach consists more particularly in designing and preparing materials for the field of energy, environment, health, and microelectronic. The projects we are developing in these four strands are briefly described below. It should be noted that the applications we are targeting will be systematically developed in close collaboration with national university, international, academic and industrial partners.
In the context of the development of metallic lithium
batteries, one of the main problems with polymer electrolytes in use today is the evolution, in opposite directions, of their mechanical properties and ionic conductivities. To address this issue, our strategy consists of imagining and preparing nanostructured block copolymers having a block acting as an electrolyte and a block providing mechanical resistance. In order to optimize the efficiency of the polymers to be synthesized, an important aspect is also devoted to the structure-composition-properties relationships. This project is currently being developed in collaboration with the Matdiv team from Madirel (ANR copolibat project) and two industrial partners (Arkema and Batscap) as part of the Genesis project.
Part of our research effort is devoted to the development of compatibilizers allowing the introduction of increasing proportions of natural polymers into synthetic materials to increase their biodegradability. The objective of this research project is to exploit the reactivity of alkoxyamines to develop methodologies for grafting chains of synthetic polymers (polystyrene, poly (methyl methacrylate)) onto polymers of the polysaccharide type. The precise characterization of the prepared materials, which is recognized as a challenge by the scientific community, will be carried out in close collaboration with the SACS team of the Institute of Radical Chemistry as part of the ANR CD2I Bioblend.
For this component, our objective is to use the potential represented by copolymers with complex architecture (block copolymers, graft copolymers, etc.) in terms of nanostructuring (in the solid state or in solution) for biology and the field of health. In this context, two research subjects will be developed:
- development of tubular guides based on synthetic polymers for the repair of peripheral nerves and the central nervous system in collaboration with the teams Patrick Decherchi (Institute of Movement Sciences, UMR 6233, Marseilles) and Francois Féron (Neurobiology of Cellular Interactions and Neurophysiopathology, UMR 6184, Marseilles). Our work is particularly focused on the synthesis of PLA-b-PHE(M)A type block co-polymers.
- development of biodegradable polymer nanoparticles functionalized by immunostimulating molecules for applications in vaccination in collaboration with the team of Bernard Verrier (Institute of Protein Biology and Chemistry, UMR 5086, Lyon). In order to achieve the desired performance levels in the targeted biological applications, a particular effort will focus on the functionalization of polymers prepared by peptides of interest (cell adhesion promoters, targeting agent, etc.).
Molecular electronics have several advantages over conventional silicon electronics. The main drivers for these fields of investigation are related to the miniaturization of components which can theoretically go down to the ultimate sizes of atoms and molecules, and the energy gains that will be associated with them. For this axis, two projects are currently being studied within the team:
- Elaboration of porous monolayer polymers in 2 dimensions and thermally stable on metallic surface. As part of the ANR cristalmol2D project developed in collaboration with IM2NP, we have developed a system based on the assembly of precursors based on boronic acid and hexafunctional phenol for the development of porous monolayer polymers in 2 dimensions and thermally stable on a silver surface. This study constitutes a major advance in the field of covalent monolayer organic coatings. Our goal now is to imagine and prepare functional building blocks allowing the functionalization of pores, with the aim of selectively immobilizing metal atoms or molecules. This is an ambitious and innovative project which should lead to an increase in knowledge of 2D self-assembly (ANR JCJC Covanet).
- Metallopolymers for light-emitting diode devices: Thanks to the integration of F. Dumur within the team, our desire is to introduce electroactive species on polymers with controlled architectures in order to generate entities likely to find applications in electronics molecular. In particular, we will focus our efforts on the introduction of iridium (III) complex into polymers to generate luminescent metallopolymers. (Collabration with G. Wantz of the Laboratory for the Integration of Material into the System (UMR 5218, Bordeaux) and Pr. C. Mayer of the Lavoisier Institute of Versailles, (UMR 8180)).
Axis 3: Precise characterization of polymers:
One of our major concerns is the determination of the chemical composition, the size of the macromolecules, or even the nanostructures of the macromolecules that we prepare. Indeed, the final properties of materials depend on these parameters. In this context, we are devoting a significant research effort to the “characterization of polymers in solution”. The use and rationalization of advanced chromatographic techniques such as Liquid Chromatography at the Critical Conditions (LC CC) and Liquid Chromatography under Limiting Conditions of Desorption (LC LCD) for the characterization of functional polymers or block and graft co-polymers is one of our priorities.
At the same time, our interest is in the small-angle X-ray scattering (DXPA) characterization of the size, shape and nanoscale organization of polymers synthesized in his team. This information is obtained both on macromolecules in solution (isolated chains, micellar solutions, etc.) and on materials in the molten state or in the solid state (films, membranes, etc.). One of the main applications concerns the determination of the structure of materials obtained from block copolymers. In particular, besides the type of structure, the scope of the order and the possible degree of orientation are all valuable information to elucidate the important parameters in the efficiency of the polymers that we prepare and to orient the nature of the materials to be synthesize.