PhMg(CH2)5MgPh and MesMg(CH2)5MgMes – divalent bis-metalated chain transfer agents (CTA) – were designed, synthesized and implemented in the polymerization of ethylene or the copolymerization of ethylene with butadiene mediated by...

metallocene • d 0 metal complexes • butadiene • polymerization • speciation • ion pairing • reactivity • DFT ABSTRACT A computational mechanistic study of the butadiene homopolymerization reaction performed with scandium and gadolinium catalysts [(2-Me-Ind)2(N(TMS)2)]M (M = Sc, Gd) in presence of [Ph3C][B(C6F5)4] or [PhNMe2H][B(C6F5)4] and Al2Et6 has been performed at the DFT level. The speciation of mono-and poly-metallic complexes involving alkylaluminum and the cationizing agent has been achieved. Their dormant or active character has been revealed. This speciation shows a thermodynamically favorable transmetalation reaction between the aryl group of [B(C6F5)4]and the alkyl group of AlR3. The reactivity of [(2-Me-Ind)(Et)M] + (M = Gd, Sc)toward monomer insertions is detailed. Computed energy profiles demonstrate the preference for cis-1,4 over trans-1,4 insertion. The influence of the counter-ion on the reactivity and selectivity of the catalyst has been investigated. For Gd-based system, the counter-ion has an impact on the reactivity and selectivity of the catalyst and cannot be omitted in the chemical model. Finally, the ability of these cationic complexes to copolymerize ethylene with butadiene is assessed and compared to neutral and efficient Nd based catalytic systems.

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 {(Me 2 Si(C 13 H 8 ) 2 )Nd(μ-BH 4 )[(μ-BH 4 )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-cobutadiene) (EBR) produced by CCT(co)P were combined and the corresponding structures were characterized.