The in-situ mechanical properties of electrochemically prepared polypy
rrole films have been measured whilst immersed in various electrolyte
solutions and under the influence of applied electrical potential. The
mechanical properties were observed to be sensitive to the oxidation
state of the polymer, with the reduced form of the polymer showing a l
ower modulus and higher elongation at break. The electrolyte cation af
fected the potential at which the ductile-brittle transition occurs.