ELECTROCHEMICAL MUSCLES - BENDING STRIPS BUILT FROM CONJUGATED POLYMERS

Conjugated polymers usually show gel properties with volume changes of 1-100% in response to various external stimuli. We find that the bend ing beam method provides an effective and sensitive way to detect and make use of these volume changes. Bipolymer strips made up of a polypy rrole (PPy) layer and a polyethylene layer bound together were prepare d. These strips bend, corresponding to volume changes in the PPy layer , during electrochemical doping and undoping of PPy in aqueous solutio ns. The bending degree and speed depend on the thickness of the two po lymer layers, and on dopants in the PPy layer and electrolytes in the solutions. We are able to obtain reversible significant bending back a nd forth in seconds. In addition, the bending beam method also provide s a novel way to measure in-situ volume changes in conjugated polymers during doping-undoping.