Actuation behaviour of polyaniline films and tubes prepared by phase inversion technique

Abstract

The phase inversion technique was used to produce polyaniline (PAn) actuators with different geometries that cannot be obtained by PAn cast from N-methyl-2-pyrrolidinone (NMP) solution in a conventional way. PAn was cast and coagulated in a water bath forming films and tubes with or without a platinum (Pt) wire helix as an interconnect. PAn was doped with hydrochloric solution (HCl, 1 M) (PAn/HCl) or methanesulfonic acid (MSA, 1 M) (PAn/MSA). In nitric acid (HNO 3 , 1 M) aqueous electrolyte, the actuation strain of PAn/HCl was 0.9 % which increased to 2.0 % and 2.7 % for the tubes without and with the Pt helix, respectively. The Pt helix helped prevent the IR drop along the actuator. Comparing with NaNO 3 (1 M) aqueous electrolyte, the use of HNO 3 aqueous electrolyte gave better actuation stability where at least 100 cycles were observed and the final actuation strain was determined by the size of dopant. Change of coagulation bath from water to NMP (30 % w/w)/water resulted in subtle difference in the Young's modulus of PAn/MSA in oxidized and reduced states. PAn prepared by phase inversion technique is porous by nature, consequently it is brittle and exhibits a low actuation stress (0.3 -0.4 MPa).

Nanostructural Aspects of Conducting‐Polymer Actuators

“…The conductivity also increased fourfold by changing the geometric shape of the actuator. The amount of strain produced with the tubular PANI actuators increased further to 2.7% when a Pt wire helix was incorporated into the tube, likely through alignment of the polymer along the wire [105].…”

“…The subsequent cathodic expansion was sizeable owing to the ability of quite bulky cations to enter the films (Figure 15.9), including the tetrabutylammonium cation which had previously proven too large to enter PPy(DBS) films. The preparation of the PANI actuators using a phase-inversion technique also created a porous microstructure, with a change in pore size seen across a rather brittle film [105].…”