High Temperature Shape Memory Polymers

High switching temperature shape memory polymers (SMPs) were developed from metal salts of sulfonated PEEK (M-SPEEK) ionomer and composites of the M-SPEEK ionomers and a fatty acid salt. The neat M-SPEEK ionomers exhibited reasonable shape memory behavior, but the composite SMPs showed very promising shape memory behavior. The composites were prepared from 70 wt % M-SPEEK (M = sodium or zinc) and 30 wt % sodium oleate (NaOl). Ionic nanodomains formed by the interactions of ionic groups provided a permanent physically cross-linked network, and strong dipolar interactions between the ionomer and a dispersed phase of crystalline NaOl provided the temporary network. A temporary shape was achieved and fixed by deforming the material above the melting temperature (T m) of NaOl and then cooling under stress to below T m. The permanent shape was recovered by reheating the material above T m without applying stress. Shape fixing efficiencies of 96% were achieved, and shape recovery reached 100%. Triple shape memory behavior was also achieved for M-SPEEK/NaOl compounds using the glass transition of the ionomer and the melting point of the NaOl as two separate switching temperatures.