RESUMEN
Coordinative chain transfer polymerization (CCTP) of ethylene and its copolymerization with 1,3-butadiene is conducted in toluene at 80 °C using a combination of {(Me2Si(C13H8)2)Nd(µ-BH4)[(µ-BH4)Li(THF)]}2 (1) metal complex and various organomagnesium compounds used as chain transfer agents including n-butyl-n-octyl-magnesium (BOMAG), n-butyl-mesityl-magnesium (n-BuMgMes), n-butyl-magnesium chloride (n-BuMgCl), n-pentyl-magnesium bromide (n-C5H11MgBr), pentanediyl-1,5-di(magnesium bromide) (PDMB) and isobutyl-magnesium chloride (i-BuMgCl). Kinetics and performance in terms of control of the (co)polymerization are comparatively discussed particularly considering the presence of ether and the nature of the organomagnesium compounds employed. Taking advantage of the well-known reactivity between nitrile and molecular organomagnesium compounds, the functionalization of the chains is further carried out by deactivation of the polymerization medium with benzonitrile or methoxybenzonitrile compounds leading to ketone ω-functionalized chains. The success of the functionalizations is extended to coupling strategies using dinitrile reagents and to the functionalization of high molar mass ethylene butadiene rubber (EBR).
RESUMEN
Block copolymers based on polyethylene (PE) and ethylene butadiene rubber (EBR) were obtained by successive controlled coordinative chain transfer polymerization (CCTP) of a mixture of ethylene and butadiene (80/20) and pure ethylene. EBR-b-PE diblock copolymers were synthesized using the {Me2 Si(C13 H8 )2 Nd(BH4 )2 Li(THF)}2 complex in combination with n-butyl,n-octyl magnesium (BOMAG) used as both the alkylating and chain transfer agent (CTA). Triblock and multiblock copolymers featuring highly semi-crystalline PE hard segments and soft EBR segments were further obtained by the development of a bimetallic CTA, the pentanediyl-1,5-di(magnesium bromide) (PDMB). These new block copolymers undergo crystallization-driven organization into lamellar structures and exhibit a variety of mechanical properties, including excellent extensibility and elastic recovery in the case of triblock and multiblock copolymers.
RESUMEN
Block copolymers based on ethylene (E) and butadiene (B) were prepared using the ansa-bis(fluorenyl) complex {Me2 Si(C13 H8 )2 Nd(BH4 )2 Li(THF)}2 in combination with (n-Bu)(n-Oct)Mg (BOMAG) as a chain-transfer agent. The diblock copolymers incorporating a soft poly(ethylene-co-butadiene) segment, called ethylene butadiene rubber (EBR), and a hard polyethylene (PE) one were obtained by simply adjusting the different feeds of monomers during the polymerization. The soluble EBR block was formed first by feeding the catalytic system dissolved in toluene at 70 °C with a mixture of ethylene and butadiene (E/B molar ratio 80 : 20). Then the feeding was stopped leading to the consumption of a large part of the residual monomers. The reactor was finally fed with ethylene to form the PE block. By varying the molar mass of the latter, it is shown that the resulting soft-b-hard block copolymers can self-assemble simultaneously to the growth of the PE block in agreement with a polymerization-induced self-assembly (PISA) mechanism. The self-assembly is discussed considering the reaction conditions, the crystallization of the PE block, and the polymerization mechanism involved.
RESUMEN
Anionic polymerization of butadiene or/and styrene is performed with lithium initiators, functional or not. The polymer chains are subsequently transferred to magnesium. The resulting polymeryl-magnesium compounds were combined with {(Me2 Si(C13 H8 )2 )Nd(µ-BH4 )[(µ-BH4 )Li(THF)]}2 metallocene complex to act as macromolecular chain transfer agents (macroCTAs) in coordinative chain transfer polymerization (CCTP) of ethylene (E) or its copolymerization (CCTcoP) with butadiene (B). Block copolymers were produced for the first time by this switch from anionic polymerization to CCTP. Hard and soft blocks such as PB, polystyrene (PS), poly(styrene-co-butadiene) (SBR) obtained by anionic polymerization and PE or poly(ethylene-co-butadiene) (EBR) produced by CCT(co)P were combined and the corresponding structures were characterized.
RESUMEN
We report the synthesis of Au(I) and Au(III) complexes, involving alcohol functionalized bis(N-heterocyclic carbene) ligands. Two short reaction pathways lead to the diimidazolium precursors, namely 1,1'-(2,6-pyridinediyl)bis[3-(2-hydroxyethyl)-1H-imidazol-3-ium]diiodide (), 3,3'(methanediyl)bis[1-(2-hydroxy-2-methylpropyl)-1H-imidazol-3-ium]dibromide () and 3,3'-(1,3-propanediyl)bis[1-(2-hydroxy-2-methylpropyl)-1H-imidazol-3-ium]bis(4-methylbenzenesulfonate) (), in which the two azolium rings are bridged by a rigid pyridine unit or an aliphatic chain (C1 or C3). The Au(I) complexes [AuI(Lpy)]2(2+)[PF6-]2 () and [AuI(LC1)]2(2+)[PF6-]2 () were obtained by direct metallation of the salts and , respectively, in the presence of sodium acetate with Au(SMe(2))Cl, followed by an anionic metathesis in the presence of KPF6. The trimethylene compound [AuI(LC3)]2(2+)[PF6-]2 () was prepared by transmetallation between the related precursor [AgI(LC3)]2(2+)[PF6-]2 () and Au(SMe2)Cl. The Au(III) complexes, [AuIII(Lpy)Br2]2(2+)[PF6-]2 (), [AuIII(LC1)Br2]2(2+)[PF6-]2 () and [AuIII(LC3)Br2]2(2+)[PF6-]2 () were generated by oxidation of the corresponding Au(I) species with an excess of elemental bromine. Complexes , [AuI(LC1)]2(2+)[Br-]2 () and have been characterized by single-crystal X-ray diffraction analyses. The electrochemical and luminescence properties of the Au(I) and Au(III) compounds have been studied.