Temperature-sensitive amorphous polyurethanes

Shape-memory polymers based on segmental polyurethanes (PUs) were synthesized from 1,3-butane diol (1,3-BD), hexamethylene diisocyanate (HDI), and 4,4'-diphenylmethane diisocyanate (MDI), and characterized in terms of thermomechanical, dynamic mechanical, theological, and thermal properties. It was found that soft segments (1,3-BD and HDI) and hard segments (1,3-BD and MDI) were well phase mixed to give a single glass transition temperature (T-g) that was easily controlled by hard segment content. With the increase in hard segment content, T-g, melt viscosity, rubbery plateau, modulus, relaxation time, and shape recovery increased, and shape fixability for repeated cycles decreased.