Ionic polymer–metal composite actuator based on sulfonated poly(ether ether ketone) with different degrees of sulfonation

The sulfonated poly(ether ether ketone) (SPEEK) membranes with different degrees of sulfonation (DS) were prepared for fabricating high-performance ionic polymer–metal composite (IPMC) actuators. The ion exchange capacity (IEC), water uptake and ion conductivity of SPEEK membranes increase accordingly with the increase of the DS of SPEEK membranes. The SPEEK membranes show much higher IEC and water uptake than those of the traditional Nafion membrane. The SPEEK actuator with the highest DS, namely SPEEK3 actuator, shows the best bending deformation under the electric stimulus. Compared with Nafion system, the SPEEK3 actuator increases at maximum blending strain under sinusoidal voltage of 3   V at 1   Hz. These greatly enhanced actuation performance indicates the SPEEK is a candidate to substitute Nafion in the field of IPMC actuator.