Synthesis and Properties of Urethane Acrylate Oligomers:  Direct versus Reverse Addition

Common urethane acrylate oligomers can be synthesized by one of two modes of addition. A polyol can be terminated on each end with diisocyanate and then capped with a hydroxy functional acrylate, direct addition, or a diisocyanate can first be reacted with a hydroxy functional acrylate, and that product can be used to terminate a polyol, reverse addition. This paper demonstrates how the mode of addition of the same reagents essentially changes the viscosity and molecular weight of the synthesized urethane acrylate oligomer.