High temperature shape memory polymers

Abstract

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 (Tm) of NaOl and then cooling under stress to below Tm. The permanent shape was recovered by reheating the material above Tm 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. © 2013 American Chemical Society.