JCJC SIMI 8 - JCJC - SIMI 8 - Chimie du solide, colloïdes, physicochimie

Free Radical Polymerization of Ethylene under mild conditions – FRaPE

Old Chemistry New Ideas! : Pushing away the limits of Free Radical Polymerization of Ethylene

Free radical polymerization of ethylene is an old industrial process allowing the synthesis of Low Density Polyethylene (LDPE) under severe temperature and pressure conditions. FRaPE project aims to refresh this polymerization by developing a polymerization process under much milder conditions. Polyethylenes with a better controlled chain structure will be obtained.

Toward controlled polymer and nanoparticles structures based on polyethylene

Research on free radical polymerization of ethylene has been rather neglected in comparison to catalytic polymerization because of technical difficulties originating from the high pressure. The milder conditions have been considered not to be efficient enough to draw the attention. We recently demonstrated the feasibility of ethylene polymerization under these conditions and the ambition of FRaPE project is clearly to further develop this process.

The FRAPE project is divided in several parts that spread from an initial approach, the suspension polymerization of ethylene in an organic solvent combining experimental (C2P2) and theoretical investigations (ICR). The process transposition to aqueous dispersed media and the development of the controlled radical polymerization of ethylene (CRPE) are technics to develop to obtain controlled architectures or complex polyethylene nanoparticules based on PE.

1) Synthesis of medium molar mass LDPE in dialkylcarbonates solvent under mild conditions (T = 70°C, P < 250 bar).
2) First example of controlled radical polymerization of ethylene (CRPE) through the RAFT technique using xanthates as controlling agents.
3) Synthesis of controlled architectures with PE segments from radical polymerization of ethylene. Examples;: dibloc copolymers EVA-b-E.
4) Synthesis of aqueous dispersions of PE nanoparticles by free radical polymerization of ethylene in water.

To develop further the synthesis of: 1) controlled polymer architectures composed of PE segments from Controlled Radical Polymerization of Ethylene (CRPE) and 2) PE nanoparticules synthesized by emulsion polymerization (potentialy hybrids or composites based on polyethylene parts).

“Enhanced Spin Capturing Polymerization of Ethylene”
C. Dommanget, C. Boisson, B. Charleux, F. D’Agosto, V. Monteil, F. Boisson, T. Junkers, C. Barner-Kowollik, Y. Guillaneuf, D. Gigmes Macromolecules 2013, 46, 29.
“Polymerization of ethylene through a Reversible Addition Fragmentation Chain Transfer (RAFT) technique” C. Dommanget, F. D’Agosto, V. Monteil
Angew. Chem., Int. Ed. 2014, acceptée pour publication / VIP (= top 5%) paper

Polyolefins (polyethylenes (PE) and polypropylene (PP)) are the largest volume polymers manufactured. Their success originates from a variety of physical properties essentially due to their crystallinity that is tuneable by the chemistry of polymerization. Low Density Polyethylene (LDPE), with a highly branched structure, is produced by free radical polymerization of ethylene (FRPE) under severe conditions (high pressure (1000-4000 bars) and high temperature (200-300°C)). Other polyolefins (HDPE or PP) are produced at low pressure (1-50 bars) and at low temperature by catalysis. The aim of the project is to open a new field of polyethylene synthesis by free radical polymerization with improved microstructures under moderate pressure (below 300 bar) and at low temperature. The challenge is important as it may lead to a better control of PE microstructures and open therefore new ranges of materials exhibiting new properties between LDPE and HDPE. Our preliminary investigations demonstrated the feasibility of FRPE at moderate pressure under slurry conditions in a solvent (which nature is crucial for polymerization efficiency) or in aqueous dispersed media. This was against the “accepted” fact that at an ethylene pressure below 300 bar and lower temperatures (<100°C) the free radical polymerization has been considered to be inefficient. The mild pressure process needs to be developed to access to high molecular weight polyethylenes with original and better controlled microstructures (branching, chain-end functionalities). For this purpose a multidisciplinary team has been put together with complementary skills and infrastructures ranging from polymerization of olefins under pressure, (controlled) radical polymerization in homogeneous and dispersed media on one hand at the C2P2 laboratory (Lyon) to radical reactivity from spectroscopic properties, kinetic behaviours and theoretical simulations of radicals on the other hand at the LCP laboratory (Marseille). The project will be divided in several parts from the slurry FRPE under mild conditions to more complex approaches combining at each stage experimental (polymerizations under moderate conditions) and theoretical investigations (radicals reactivity and computational modelling). In a first step we will aim to better understand in order to improve slurry FRPE with the aim to access either high molecular weight PE or PE with high ratios of chain-end functionalization (if necessary further used as macromonomers). New approaches will then focus on the intensification of the transposition of FRPE to aqueous dispersed media and on the development of controlled free radical polymerization of ethylene (CRPE) to better control PE microstructures. Controlled architectures based on polyethylene segments by CRPE or on the other hand to nanoparticles (especially hybrid or composite particles based on a polyethylene part) by emulsion polymerization will be thus obtained. Copolymerization of ethylene with polar monomer will be also envisaged.

Project coordination

Vincent MONTEIL (UNIVERSITE CLAUDE BERNARD - LYON I) – monteil@lcpp.cpe.fr

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.

Partner

C2P2 UNIVERSITE CLAUDE BERNARD - LYON I

Help of the ANR 199,992 euros
Beginning and duration of the scientific project: October 2011 - 42 Months

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