Sulfonated Poly(ether ether ketone) Ionomers and Their High Temperature Shape Memory Behavior

High temperature shape memory polymers (SMP) were prepared from metal salts of a sulfonated poly(ether ether ketone) ionomer, M-SPEEK, using cations of varying valence from one to four. The ionomers were prepared by neutralizing a SPEEK with 18 mol % sulfonation (ion exchange capacity = 0.60 mequiv/g) with Na+, Zn2+, Ba2+, Al3+, and Zr4+. The glass transition temperatures (T-g) of M-SPEEK ionomers increased with increasing Coulomb energy of the ion pair, which provided a range of switching temperatures for shape memory behavior of 224 to 288 degrees C. The ionomers were completely amorphous and thermally stable to similar to 300 degrees C, at which desulfonation occurred. The modulus of the ionomers above T-g was high, 1-100 MPa, due to dipole dipole or ionic supramolecular bonding of the sulfonate groups that formed the permanent network for shape memory. The water absorption of the ionomers ranged from about 5 to 16 wt %, depending on the nature of the cation. Na-SPEEK exhibited relatively poor shape memory behavior with fixity (F) and recovery (R) values of about 8096 and 45%, respectively, but the ionomers prepared with multivalent cations had F and R values greater than 9096 that were reproducible over multiple shape memory cycles.