Amine-Functionalized Polybutadiene Synthesis by Tunable Postpolymerization Hydroaminoalkylation.

Early transition metal-catalyzed hydroaminoalkylation is a powerful single-step method to selectively add amines to polybutadienes, offering an efficient strategy to access amine-functionalized polyolefins. Aryl and alkyl secondary amines were used with a tantalum catalyst to functionalize both 28 wt% ( PBD13 ) and 70 wt% ( PBD50 ) 1,2-polybutadiene polymers. The degree of amination was controlled by modifying amine and catalyst loading in both small- and multigram-scale reactions. The vinyl groups of 1,2-polybutadiene were aminated with ease, and unexpectedly the hydroaminoalkylation of challenging internal alkenes of the 1,4-polybutadiene unit was observed. This unanticipated reactivity was proposed to be due to a directing group effect. This hypothesis was supported with small-molecule model substrates, which also showed directed internal alkene amination. Increasing degrees of amination resulted in materials with dramatically higher and tunable glass transition temperature ( T g ) values, due to the dynamic cross-linking accessible to hydrogen-bonding, amine-containing materials. Primary amine-functionalized polybutadiene was also prepared, demonstrating that a broad new class of amine-containing polyolefins can be accessed by postpolymerization hydroaminoalkylation.