ELECTROCHEMICAL APPLICATIONS OF THE BENDING BEAM METHOD, A NOVEL WAY TO STUDY ION-TRANSPORT IN ELECTROACTIVE POLYMERS

A novel method, the bending beam method (BBM), is introduced to study ion transport in an electroactive polymer, polypyrrole (PPy). Volume c hanges in PPy are studied by observing the bending behavior of a bipol ymer laminate strip, made of a PPy layer and a polyethylene layer, dur ing electrochemical redox of the PPy. On reduction in an aqueous solut ion of lithium perchlorate, methane sulfonate doped and perchlorate do ped PPy's shrink rapidly, whereas a dodecylbenzene sulfonate doped PPy swells rapidly. A tosylate doped PPy undergoes initial rapid swelling followed by rapid shrinking. We interpret these phenomena as due to d ifferent ion transport modes. Relaxation is generally observed to be a ssociated with volume shrinking in all reduced PPy's and is attributed to a structural relaxation in the polymer matrix. The BBM technique p rovides a new sensitive way to detect in situ mass transport in electr oactive polymers.