Catalytic living ring-opening metathesis polymerization

In living ring-opening metathesis polymerization (ROMP), a transition-metal–carbene complex polymerizes ring-strained olefins with very good control of the molecular weight of the resulting polymers. Because one molecule of the initiator is required for each polymer chain, however, this type of polymerization is expensive for widespread use. We have now designed a chain-transfer agent (CTA) capable of reducing the required amount of metal complex while still maintaining full control over the living polymerization process. This new method introduces a degenerative transfer process to ROMP. We demonstrate that substituted cyclohexene rings are good CTAs, and thereby preserve the ‘living’ character of the polymerization using catalytic quantities of the metal complex. The resulting polymers show characteristics of a living polymerization, namely narrow molecular-weight distribution, controlled molecular weights and block copolymer formation. This new technique provides access to well- defined polymers for industrial, biomedical and academic use at a fraction of the current costs and significantly reduced levels of residual ruthenium catalyst

Oligomérisation, Polymérisation et Hydrophosphorylation Catalytiques d'Oléfines et de Diènes

Thèse de Doctorat de l'Université de Rennes

Efficient and Selective Rhodium-Catalyzed Hydrophosphorylation of Dienes

International audienc

Controlled Radical Polymerization of Conjugated 1,3-Dienes with Methyl 1,3-Butadiene-1-phosphonate

International audienc

Functional Syndiotactic Poly(β-hydroxyalkanoate)s via Stereoselective Ring-Opening Copolymerization of rac-β-Butyrolactone and rac-Allyl-β-Butyrolactone

International audienc

Mixed aluminum-magnesium-rare earth allyl catalysts for controlled isoprene polymerization: modulation of stereocontrol

International audienc

Synthesis of Poly(vinylidene fluoride)-b-poly(styrene sulfonate) Block Copolymers by Controlled Radical Polymerizations

International audienceBlock copolymers based on poly(vinylidene fluoride), PVDF, and a series of poly(aromatic sulfonate) sequences were synthesized from controlled radical polymerizations (CRPs). According to the aromatic monomers, appropriate techniques of CRP were chosen: either iodine transfer polymerization (ITP) or atom transfer radical polymerization (ATRP) from PVDF-I macromolecular chain transfer agents (CTAs) or PVDF-CCl3 macroinitiator, respectively. These precursors were produced either by ITP of VDF with C6F13I or by radical telomerization of VDF with chloroform, respectively. Poly(vinylidene fluoride)-b-poly(sodium styrene sulfonate), PVDF-b- PSSS, block copolymers were produced from both techniques via a direct polymerization of sodium styrene sulfonate (SSS) monomer or an indirect way with the use of styrene sulfonate ethyl ester (SSE) as a protected monomer. Although the reaction led to block copolymers, the kinetics of ITP of SSS showed that PVDF-I macromolecular CTAs were not totally efficient because a limitation of the CTA consumption (56%) was observed. This was probably explained by both the low activity of the CTA (that contained inefficient PVDF-CF2CH2AI) and a fast propagation rate of the monomer. That behavior was also noted in the ITP of SSE. On the other hand, ATRP of SSS initiated by PVDF-CCl3 was more controlled up to 50% of conversion leading to PVDF-b-PSSS block copolymer with an average number molar mass of 6000 g.mol-1

Bis(phosphinimino)methanide borohydride complexes of the rare earth elements as initiators for the ring-opening polymerization of -caprolactone: combined experimental and computational investigations

International audienceRare-earth-metal borohydrides are known to be efficient catalysts for the polymerization of apolar and polar monomers. The bis-borohydrides [{CH(PPh2NSiMe3)2}La(BH4)2-(THF)] and [{CH(PPh2NSiMe3)2}Ln-(BH4)2] (Ln=Y, Lu) have been synthesized by two different synthetic routes. The lanthanum and the lutetium complexes were prepared from [Ln(BH4)3-(THF)3] and K{CH(PPh2NSiMe3)2}, whereas the yttrium analogue was obtained from in situ prepared [{CH(PPh2NSiMe3)2}YCl2]2 and NaBH4. All new compounds were characterized by standard analytical/spectroscopic techniques, and the solid-state structures were established by single-crystal X-ray diffraction. The ring-opening polymerization (ROP) of ε-caprolactone initiated by [{CH(PPh2NSiMe3)2}La(BH4)2(THF)] and [{CH(PPh2NSiMe3)2}Ln(BH4)2] (Ln=Y, Lu) was studied. At 0°C the molar mass distributions determined were the narrowest values (Mw/Mn = 1.06-1.11) ever obtained for the ROP of ε-caprolactone initiated by rare-earth-metal borohydride species. DFT investigations of the reaction mechanism indicate that this type of complex reacts in an unprecedented manner with the first B-H activation being achieved within two steps. This particularity has been attributed to the metallic fragment based on the natural bond order analysis

Functional Elastomers via Sequential Selective Diene Copolymerization / Hydrophosphorylation Catalysis

International audienc