| Research Abstract |
Purposes of the study are to clarify mechanisms of chemomechanical deformation, i.e.expansion and contraction of conducting polymers upon electrochemical oxidation/reduction, and to fabricate actuators using conducting polymers.
In 1997, the degree, response and force of chemomechanical deformation in conducting polymer, polyaniline were investigated in various anions of aqueous solution. As results, mechanisms of deformation are found to be (1) doping and undoping of bulky anions, (2) conformational deformation of polymer resulted from delocalization of and (3) electrostatic repulsion between polycations. In these mechanisms, (1) is found to be predominant, however, (2) or (3) is suggested to play a role for the deformation.
In 1998, self-doped polyaniline and polyaniline with giant anions are studied to elucidate the existence of mechanisms (2) and (3). Sulfonic polyaniline which is self-doped was synthesized and measured in the cyclic voltammogram and chemomechanical deformation. In the oxidation process, once the film expands followed by contraction at the quasi-equilibrium state. The expansion is explained by taking the delocalization of pi electrons or electrostatic repulsion between polycations. Then, structural relaxation takes place by the strong negative sulfonic ion, which attracts pi electrons of benzene ring, resulting in shrinking of polymer film.
Polyaniline film polymerized by constant current mode with a giant anion of camphor sulfonic acid (CSA) was found to keep CSA anion in film during the redox reactions. the result indicates that during oxidation process the film slightly expand due to mechanism (2) and (3), even protons are excluded from the film.
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