Electromechanical response of a soft and flexible actuator based on polyaniline particles embedded in a cross-linked poly(dimethyl siloxane) network

Electroviscoelastic characteristics of poly (dimethyl siloxane) (PDMS) networks containing camphorsulfonic acid (CSA) — doped polyaniline (PANI) particles were investigated. Samples were prepared by dispersing fine PANI particles in a cross-linked PDMS matrix. Rheological properties of the PANI/PDMS composites were studied in oscillatory shear mode to elucidate the effects of electric field strength, particle concentration, and operating temperature on the electromechanical response. On application of an electric field the storage modulus G′ increases by an amount ▵G′ ∼ 10–50%, depending on PANI volume fraction, as the field strength is increased to 2 kV/mm. This increase in modulus is only partially reversible (about 37.5% recovery) on removal of the applied field, indicating that a quasi-permanent polarization is induced in the PANI particles. It is presumed that the increase in storage modulus originates in an electrostriction effect due to the attractive forces between polarized PANI particles embedded in the PDMS network. The temperature dependence of ▵G′ shows a maximum at T ∼ 325 °K, corresponding to the temperature range where the conductivity of PANI attains its maximum value. Finally, we report observations of the electromechanical response of a PANI/PDMS composite film, suspended in silicone oil between copper electrodes, which is manifested upon application of an electric field as a field-dependent deflection.