Physical and Chemical Probes of the Bond Strength between Trialkylboranes and Amines and Their Utility as Stabilized Free Radical Polymerization Catalysts

Abstract

Trialkylboranes are established polymerization catalysts in part due to their ability to generate radicals at room temperature when exposed to oxygen. This capability also creates the conditions for a fire hazard if the oxidation does not commence under controlled conditions. One way to achieve control of the catalyst reactivity is to react trialkylborane with an amine and so hinder the route by which oxygen initially interacts with the borane. Because of its dative nature, the borane−amine bond can be broken at relatively low temperatures; this temperature can be tuned by controlling the strength of the bond. This article details the electronic and structural amine features that result in more stable trialkylborane amine bonds, demonstrates several methods to physically probe the bond strength, and correlates the methods to each other. Last, the relationship of trialkylborane amine bond strength to catalyst and adhesion promoter efficacy is presented.