One of the most important scientific and industrial challenges in polymer chemistry is the synthesis of materials with well-defined composition and macromolecular architectures, which are in principle accessible by living polymerization methods. The recent development of controlled radical polymerization (CRP) has greatly expanded the scope of monomers that can be incorporated in well-defined macromolecular architectures but there are still important bottlenecks. CRP functions through dynamic equilibrium between growing active chains and latent chains bonded to a moderating agent, the nature of which is adapted to the monomer being polymerized (i.e. to the reactivity of the associated radical). Thus, monomers with very different reactivity (More Activated Monomers or MAMs on one side, Less Activated Monomers or LAMs on the other) cannot be controlled with the same moderating agent. This limits the possibility of making block PMAM-b-PLAM architectures of interest for multiple innovative applications, by sequential addition. Among the various CRP strategies, reversible addition-fragmentation chain-transfer (RAFT) polymerization is the most versatile and promising for industrial implementation.
The present project proposes to remove this bottleneck by developing switchable RAFT agents that can function in two forms, one suitable for LAMs and the other one for MAMs, by development of a new type of RAFT agent based on trivalent phosphorus and a switch controlled by chemical modification at the P atom by either PV/PIII conversion, by coordination chemistry or by a redox process on the incorporated metal. It is implemented by the joint efforts of the P3R team, a world leader in RAFT polymerization of LAMs with strong industrial experience, and the LCAC team, which brings expertise in functionalized P ligands and coordination chemistry, including the application of metal complexes in a range of CRP processes.
The project is divided into 4 scientific tasks. Task 1 is the synthesis of several new tunable RAFT agents that can be switched to a different form, one form being suitable to control MAMs and the other form being able to control LAMs. In Task 2, the controlling ability of these new RAFT agents will be tested to assess the monomer compatibility for each pair of partners that are related to each other by a chemical switch. Task 3 will optimize the switching phase by investigating the chemical change on the chain-end for the single-block polymers developed in Task 2. Finally, in Task 4 a variety of new block copolymers will be synthesized by sequential addition, the RAFT agent will be removed from the chain end, and the polymers will be purified. A further aim of Task 4 is to develop protocols for sequential monomer addition (with switch) in aqueous media. Finally, an ultimate challenge of this project will be to access block copolymers containing one ethylene-rich block. These investigations will lead to the development of previously inaccessible added-value polymers by simplified protocols that only require the use of a single, easily switchable, RAFT agent.
Monsieur Stéphane MAZIERES (CNRS/Laboratoire des Interactions Moléculaires et Réactivités Chimique et Photochimique)
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
CNRS MIDI PYR / LCC Laboratoire de Chimie de Coordination
CNRS MIDI-PYR /IMRCP CNRS/Laboratoire des Interactions Moléculaires et Réactivités Chimique et Photochimique
Help of the ANR 395,183 euros
Beginning and duration of the scientific project: December 2016 - 48 Months