There is no polyurethane monomer leading to polyurethane polymers. This is in contrast to a polymer like polyethylene which is derived from the polymerization of ethylene monomer and results in a homopolymer of linear or branched structure. Polyurethane polymers result from the addition reactions of isocyanate molecules of different types reacting with active hydrogen functional molecules or polymers that result in phase separated, block copolymers. The size, the shape and the intermolecular interactions of the isocyanates and the polyols used to make polyurethanes affects how phase separated segments will order themselves and how they will move in relation to each other, which will dictate the physical properties of that polyurethane polymer. This webinar is designed to provide an overview of how the selection of isocyanate structure and reactivity, combined with the proper selection of polyols, allows the polyurethane formulator to design and tailor the physical properties of polyurethanes for specific applications.