Thiol-ene Reaction In Ckemistry of Polyolefins – TRICKY

The present project is related to the synthesis of polyolefin based materials incorporating polar segments Polyolefins (mainly polyethylene (PE) and polypropylene (PP)) are the largest volume thermoplastics manufactured in the world and new polymer materials based on these polymers could strongly impact our life. The excellent combination of chemical and physical properties of polyolefins along with low cost makes this class of polymer very attractive for commercial purposes. For more than 50 years, the modification of polyolefins has been both an academic and an industrial challenge. The scientific difficulty relies on the fact that these materials industrially produced mainly by catalytic olefin polymerization cannot or only hardly incorporate functional groups. Therefore, the development of new strategies to incorporate polar segments into polyolefins in a controlled fashion is one of the long term goals in polymer chemistry since the targeted materials would enable to produce new architectures with many desirable properties. One way is the synthesis of reactive polyolefins. The functional groups introduced onto the polyolefin are used in a second step to initiate another polymerization technique (anionic or radical). The resulting functionalized polyolefins can thus serve as building blocks for constructing multi-segmented polymers. A second step method employing a controlled radical polymerization (CRP) technique opens the way to the synthesis of polyolefins bearing polar segments with controlled characteristics (chain length, polydispersity, architecture, etc.). The difficulty relies on an efficient and simple way of introducing the appropriate end functionalities into polyolefins. To address these issues and fulfill the requirements of efficacy and simplicity, we propose to extrapolate an old but undoubtedly powerful concept based on thiol/ene chemistry. This cheap and very robust chemistry consists in binding through a thioether link two molecules by reacting a thiol function present on one molecule with an ene group of the second molecule. As a result, appropriately designed polyethylenes (containing ene or thiol end groups) will be used for further functionalization. Four our purpose, the polyethylenes obtained after functionalization must serve as building blocks for more complex architectures based on polyolefins. This could be achieved if the resulting functionalized polyethylenes are control agents, initiators or co-monomers in another polymerization technique more tolerant to functional groups than coordination catalysis or if they readily react with the suitable end group of a polar polymer. The preparation of the polar segments will be performed by controlled free radical polymerization techniques using two of these techniques namely Nitroxide Mediated and Reversible Addition Fragmentation chain Transfer Polymerizations (NMP and RAFT respectively). We thus want to investigate the use of thiol/ene chemistry and CRP techniques to reach the goal of this project according to three different but complementary ways: (1) to synthesize functional polyethylenes that can directly act as macro-control agents in NMP or RAFT polymerization using thiol or ene containing polyethylenes (2) to synthesize ene end functionalized polar polymer chains using NMP and RAFT polymerization and react them with thiol containing polyethylenes. (3) to synthesize thiol end functionalized polar polymer chains using RAFT polymerization and react them with ene containing polyethylenes.