Water vapor permeability of shape memory polyurethane with amorphous reversible phase

Shape memory thermoplastic polyurethanes (TPUs), based on amorphous soft se gment from the reaction of hexamethylene diisocyanate and 1,2-butane diol, and the crystalline hard segment from 4,4'-methylenediphenyl diisocyanate a nd 1,6-hexanediol, were modified by hydrophilic segments, diol-terminated p oly(ethylene oxide) or dimethylol propionic acid (DMPA). Differential scann ing calorimetry, dynamic mechanical testing, tensile testing, and the measu rement of shape memory effect, water swell, and water vapor permeability we re carried out to examine these TPUs. The hydrophilic segment increased the hysterisis in shape memory effect by reducing the crystallinity of the har d segment. The neutralized DMPA unit enhanced the sensitivity of the thermo responsive water vapor permeability (WVP) by amplifying the increase of WVP at the temperature range above the glass transition temperature. (C) 2000 John Wiley & Sons, Inc.