Tunable electrical and mechanical responses of PDMS and polypyrrole nanowire composites

Abstract

A generic experimental procedure is presented in this work to enhance the electrical responses of polydimethylsiloxane (PDMS) through incorporation of conducting polymer nanowires, while maintaining the desirable mechanical flexibility of PDMS. The conducting polypyrrole (PPy) nanowires are synthesized using a template method. The dielectric constants of the composites are characterized by impedance measurements, and the effect of nanowire concentration is investigated by the percolation theory. Using a continuous hyperbolic tangent function, critical volume fraction is estimated to be 9.6 vol%, at which an 85-fold enhancement in the dielectric constants is achieved. The viscoelastic properties of the composites are characterized by the stress relaxation nanoindentation tests, and the effect of nanowire concentration on the elastic modulus of composites is found to deviate significantly from the Wang–Pyrz model at the critical volume fraction. The tunable multifunctionality of PDMS composites that possess significantly enhanced electrical and moderate viscoelastic responses is desirable for many sensing and actuation applications.