Coordinative Chain Transfer Polymerization of Butadiene with Functionalized Aluminum Reagents

Abstract

Functionalized aluminum alkyls enable effective coordinative chain transfer polymerization with selective chain initiation by the functionalizedalkyl. (w-Aminoalkyl)diisobutylaluminum reagents (12 examples studied) obtained by hydroalumination of a-amino-w-enes with diisobutylaluminum hydride promote the stereoselective catalytic chain growth of butadiene on aluminum in the presence of Nd(versatate) 3 , Cp* 2 Nd(allyl), or Cp* 2 Gd(allyl) precatalysts and [PhNMe 2 H + ]/[B(C 6 F 5 ) 4 À ]. Carbazolyl-and indolylaluminum reagents result in efficient molecular weight control and chain initiation by the aminoalkyl rather than the isobutyl substituent bound to aluminum. As confirmed for (3-(9H-carbazol-9yl)propyl)-initiated polybutadiene (PBD), for example,b y deuterium quenching studies,p olymer chain transfer by bhydride transfer is negligible in comparison to back-transfer to aluminum. Scheme 1. Concept and current status of coordinative chain transfer polymerization. MGM = main group metal, M = transitionm etal, PE = polyethylene, PBD = polybutadiene.

Pyridine-amido aluminum catalyst precursors for 1,3-butadiene transition-metal-free stereospecific polymerization

“…According to previous reports, chain termination and chain transfer at high temperatures are much faster than chain propagation, and the active species become unstable, which can explain the poor activity at high temperatures. 51–56 Considering that free radical polymerization cannot be ignored at 50 °C, the product obtained at this temperature may not reveal the catalytic nature of the catalyst. 57–59 Increasing the amount of MAO could improve the catalytic activity to some extent, which was consistent with most coordination polymerization systems (Table 2, entries 4–6).…”

“…According to previous reports, chain termination and chain transfer at high temperatures are much faster than chain propagation, and the active species become unstable, which can explain the poor activity at high temperatures. [51][52][53][54][55][56] Considering that free radical polymerization cannot be ignored at 50 °C, the product obtained at this temperature may…”