Synthesis of Stereodiblock Polybutadiene Using Cp*Nd(BH4)2(thf)2 as a Catalyst

Abstract

Butadiene polymerization, in both a highly cis-and trans-specific manner, was achieved by using a Cp*Nd(BH 4 ) 2 (thf) 2 -Bu 2 Mg system as an initiator. The cis-/trans-ratio can be tuned by the amount of trialkylaluminum-depleted modified methylaluminoxane (dMMAO). The cis-regularity of the polymer was much higher than those obtained by Nd(BH 4 ) 3 (thf) 3 . The molecular weight of cis-regular polymer was increased according to polymer yield, showing that there was no termination or chain transfer reaction during the polymerization. Synthesis of stereodiblock polybutadiene, which showed a high melting temperature (T m ) compared with stereodiblock polyisoprene, was also performed by the addition dMMAO during the polymerization.

Dienes Polymerization: Where We Are and What Lies Ahead

“…Catalytic systems completely similar to the one described above have been subsequently reported in the literature. , Stereoblock polybutadienes have also been obtained with catalytic systems based on neodymium and transition metals (Cr, Fe, Co) . Stereoblock polymers have also been prepared in the case of isoprene, using catalytic systems based on cobalt ,, and lanthanides (Y, Nd). ,,,, …”

“…The recent discovery and introduction of new catalytic systems having not only high catalytic activity and selectivity but also some living features and the ability to change their selectivity during polymerization while maintaining their living nature can be extremely useful for this purpose. The strategies adopted to modify the selectivity during the polymerization runs are of different types, ranging from adding a specific ligand to changing the cocatalyst (i.e., different type of aluminum alkyl) and from increasing the Al/Mt molar ratio to modifying the polymerization temperature. ,,− …”

Catalysts for the Controlled Polymerization of Conjugated Dienes

“…The absence of termination or chain transfer reaction during the polymerization, deduced from the regular increase of Mn with the polymer yield, allowed further the synthesis of stereodiblock polybutadiene. This was achieved by adding dMMAO in a second time, to a polymerization mixture firstly initiated with Cp*Nd(BH 4 ) 2 (THF) 2 -Bu 2 Mg [19]. The stereodiblock polybutadiene thus synthesized displayed higher cis-regularity of the polydiene sequence, along with a broader difference of Tm and Tg temperatures, compared with the cis/transstereodiblock polyisoprene reported previously using a Nd/Mg/Al combined catalyst system based on Nd(BH 4 ) 3 (THF) 3 [20].…”

Effect of Ancillary Ligands as a Part of Counteranion in Neodymium-Catalyzed Isoprene Polymerization

“…Mixed halide/pseudohalide complexes of rare-earth metals are currently gaining attention because they integrate different functionalities and reactivities . Among pseudohalides, borohydrides are often applied to stable precursors for the controlled polymerization of conjugated dienes. − Borohydride anions are more electron-donating than chloride, coordinating to the metal center in an η 3 - or η 2 - manner. BH 4 – , like chloride, sometimes bridges two lanthanide metals, but such cluster formation would be prevented by the introduction of bulky substituents on boron.…”