Effects of Isophorone Diisocyanate on the Thermal and Mechanical Properties of Shape-Memory Polyurethane Foams

Previously developed shape‐memory polymer foams display fast actuation in water due to plasticization of the polymer network. The actuation presents itself as a depression in the glass‐transition temperature when moving from dry to aqueous conditions; this effect limits the working time of the foam to 10 min when used in a transcatheter embolic device. Reproducible foams are developed by altering the chemical backbone, which can achieve working times of greater than 20 min. This is accomplished by incorporating isophorone diisocyanate into the foam, resulting in increased hydrophobicity, glass transitions, and actuation time. This delayed actuation, when compared with previous systems, allows for more optimal working time in clinical applications. Porous, low‐density shape‐memory polymers are developed with tunable transition temperatures and actuation rates by altering the polymer backbone from trimethyl‐1,6‐hexamethylene diisocyanate (a) to isophorone diisocyanate (b) at varying concentrations.