Thermoplastic polyurethanes were synthesized from poly(propylene glycol)-block-poly(ethylene glycol) polyols and hybrid hard segments that combined at least two different chain extenders. The combination of hard segments allowed for modification of elastomer performance and processing not achievable by any single hard segment. The combination of hard segments modulated hard-segment energies that were directly related to elastomer performance. Special attention is paid to obtaining optically transparent elastomers with this technique. (C) 2003 Wiley Periodicals, lnc. J Polym Sei Part A: Polym Chem 42: 271-278, 2004