A dual part polymerizable composition is provided including a first part containing at least one triorganoborane-amine complex having the structure Z—NHR1—B(R2)3 wherein: Z is an organic group; R1 is H or an organic group; and each R2 is independently an organic group bound to the boron atom through a carbon atom. The composition also includes a second part containing a polymerizable component and acidified nanoparticles including acid groups, where each acidified nanoparticle includes an inorganic core and acid groups. The acid groups include acid stabilizers and/or acid groups covalently bound to the inorganic core through an organic group. Each inorganic core is typically an inorganic oxide core, e.g., silica, zirconia, or alumina.