Electrochemical Soft Actuator: Deciphering the Difference in the Characteristics of Polaronic and Bipolaronic Forms of Polyaniline

Rani, D and Vijaya Kumara, A and Srinivasan, S (2022) Electrochemical Soft Actuator: Deciphering the Difference in the Characteristics of Polaronic and Bipolaronic Forms of Polyaniline. In: Langmuir, 38 (31). pp. 9575-9586.

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Abstract

Polyaniline (PANI) has been projected as an efficient electrochemical actuator due to its ease of synthesis, lightweight, biocompatibility, low cost, and possible low operating potential and high stress generation. However, challenges such as low inherent ionic and electronic conductivity of the polymer lead to small accumulation of ions and high ionic diffusion path length inside the polymer remain. In the present study, a highly conjugated, planar, conducting polaronic form of PANI with a nanofiber morphology is synthesized using in situ electrochemical polymerization on a reduced graphene oxide (rGO) electrode. The polymerization is carried out in the Schaefer mode at the air-water interface under controlled surface pressure in a Langmuir trough. Electrochemical, UV-visible, XPS, and Raman spectroscopic studies confirm the formation of the planar polaronic PANI form. Polymerization without surface pressure leads to the bipolaronic form of PANI. The two forms are subsequently used to understand their contributions toward electrochemical actuation in a bilayer configuration. The conducting polaronic PANI/EGO (exfoliated graphene oxide) exhibits a remarkably larger total angular displacement of 220° in aqueous 1 M NaClO4during a potential scan in the range ±0.9 V than the bipolaronic counterpart which exhibits a total angular displacement of 125°. Current imaging in the scanning electrochemical microscopy mode confirms a high volumetric expansion in the case of the polaronic form as compared to its bipolaronic counterpart. Raman spectroscopy reveals the oxidation to the emeraldine form in the polaronic PANI and to the pernigraniline form in the bipolaronic form during actuation. Electrochemical impedance spectroscopy study evidences the existence of a small charge transfer resistance with high bulk capacitance for the polaronic structure. © 2022 American Chemical Society. All rights reserved.

Item Type:	Journal Article
Publication:	Langmuir
Publisher:	American Chemical Society
Additional Information:	The copyright for this article belongs to the American Chemical Society.
Keywords:	Actuators; Air; Biocompatibility; Chlorine compounds; Electrochemical impedance spectroscopy; Graphene; Morphology; Phase interfaces; Polymerization; Raman spectroscopy; Scanning electron microscopy; Scanning probe microscopy; Sodium compounds; Spectroscopic analysis, Angular displacement; Electrochemical actuators; Electrochemicals; Electronic conductivity; High stress; Low-costs; Potential stress; Soft actuators; Stress generation; Surface pressures, Charge transfer
Department/Centre:	Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited:	06 Oct 2022 09:49
Last Modified:	06 Oct 2022 09:49
URI:	https://eprints.iisc.ac.in/id/eprint/77188

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