Bis-HEMA Poly(1,4-Butanediol Adipate)/IPDI Copolymer is a urethane polymer formed by a multi-step process. First, a polyester is made by condensing 1,4-Butanediol and Adipic Acid. This polyester is reacted with Isophorone Diisocyanate. The resulting polymer is end-capped with HEMA.