Lateral Growth of Polypyrrole Electropolymerized along Hydrophobic Insulative Substrates

Abstract

Effect of hydration property of insulative surfaces on two-dimensional growth of polypyrrole thin film along the surfaces was studied. When a platinum rod electrode was simply placed on an insulative hydrophobic substrate immersed in an aqueous solution containing pyrrole as monomer, a polypyrrole thin film started to grow two-dimensionally along the surface toward the counter electrode which was a platinum ring electrode placed around the insulative substrate. Such lateral growth of polypyrrole was not observed on a hydrophilic surface. The mechanism of the lateral growth is significantly different from that proposed for metal thin films grown along air/liquid or liquid/liquid interfaces. The lateral growth of polypyrrole seems to be induced by a highly concentrated pyrrole in the vicinity of hydrophobic surfaces. Finally, we have demonstrated that the lateral growth of polypyrrole recognizes the boundary of hydration property on a glass substrate on which hydrophilic and hydrophobic regions coexist.Conductive thin films have attracted keen attention in materials science. In electrochemistry, two-dimensional growth of conductive thin films such as metals and polymers at air/liquid or liquid/liquid interfaces is a well-known technique. 1-13 For the sake of the utilization of thin films as a material, thin films must be transferred onto solid surfaces, but the transfer without destroying the microstructure is quite difficult. Therefore, direct deposition of conductive thin films on solid surfaces has been studied intensively. Electroless deposition is often used to form metal thin films on insulative surfaces. This technique requires the seeding process in advance of electroless deposition. 14 Thus, a much easier technique for the preparation of conductive thin films on insulative surfaces is desired.To the best of our knowledge, studies on the formation of conductive thin film directly on insulative surfaces are very limited. The easiest strategy is the utilization of a thin electrolyte solution sandwiched with two glass slides. 15 For the enhancement of surface conductivity, insulative surfaces modified by isolated gold nanoparticles are often utilized to form gold thin films. [16][17][18] It has also been shown that insulative surfaces modified with a self-assembled monolayer on which metal complex ions preferentially adsorb are effective for two-dimensional growth of a metal thin film. 19,20 The self-assembled monolayer enhances the formation of a high concentration layer of metal ions on the insulative surface. As a result, formation of a metal thin film directly on the insulative surface has been achieved.In the present letter, we discuss how the hydration property of insulative surfaces affects two-dimensional growth of conductive polymer thin films along the insulative surfaces. Studies using thin-layer cells or modification of insulative surfaces with peptide for an enhancement of monomer adsorption have been reported. 21,22 In contrast, the present study reports another mechanism to control the growth mo...

Bicontinuous nanotubular graphene–polypyrrole hybrid for high performance flexible supercapacitors

“…The large curvature gradient of graphene results in a high density of topological lattice defects, which obviously enhance the wetting ability for easy deposition of PPy coatings [34,36]. Furthermore, since the pyrrole monomer is a hydrophobic solute in aqueous solutions, weakly hydrated pyrrole monomer solutes in hydrophilic aqueous solution are segregated from the solution and concentrated on hydrophobic surface [37] and hence a PPy layer can be formed as a continuous uniform coating on the graphene surface.…”

Superhydrophobic‐Substrate‐Assisted Construction of Free‐Standing Microcavity‐Patterned Conducting Polymer Films

“…Furthermore, the hydrophobic pyrrole monomers tended to aggregate at the triphase interface (left in Figure 3c ). [ 28 ] Electrochemical oxidation polymerization occurs at the triphase interface when the experimental setup is powered on, while electrochemical reduction hydrogen evolution occurs at the platinum ring electrode. The corresponding chemical equations are as follows:…”