High Proton Conductivity in the Molecular Interlayer of a Polymer Nanosheet Multilayer Film

Abstract

High proton conductivity was achieved in a polymer multilayer film with a well-defined two-dimensional lamella structure. The multilayer film was prepared by deposition of poly(N-dodecylacryamide-co-acrylic acid) (p(DDA/AA)) monolayers onto a solid substrate using the Langmuir-Blodgett technique. Grazing-angle incidence X-ray diffraction measurement of a 30-layer film of p(DDA/AA) showed strong diffraction peaks in the out-of-plane direction at 2θ = 2.26° and 4.50°, revealing that the multilayer film had a highly uniform layered structure with a monolayer thickness of 2.0 nm. The proton conductivity of the p(DDA/AA) multilayer film parallel to the layer plane direction was 0.051 S/cm at 60 °C and 98% relative humidity with a low activation energy of 0.35 eV, which is comparable to perfluorosulfonic acid membranes. The high conductivity and low activation energy resulted from the formation of uniform two-dimensional proton-conductive nanochannels in the hydrophilic regions of the multilayer film. The proton conductivity of the multilayer film perpendicular to the layer plane was determined to be 2.1 × 10(-13) S/cm. Therefore, the multilayer film showed large anisotropic conductivity with an anisotropic ratio of 2.4 × 10(11).

In-plane oriented highly ordered lamellar structure formation of poly(N-dodecylacrylamide) induced by humid annealing

“…Recently, we have reported that the two-dimensional proton nanochannel constructed in the interlayer of pDDA nanosheet assembly shows a fast proton conduction. 19 A similar two-dimensional nanochannel can be simply prepared by the present process, which suggests the lamellar lm has a potential for high proton conductive membranes. Applications of the highly oriented lamellar lm to ion transfer materials are now in progress.…”

“…Recently, we reported a high proton-conductive lm using a poly(N- dodecylacrylamide-co-acrylic acid) LB lm. 19 The high proton conduction in the copolymer LB lm can be attributed to formation of a two-dimensional (2D) proton-conductive nanochannel in the interlayer of the LB lm by humid annealing. Therefore, it is important to investigate the effect of humidity on the nanostructure of pDDA to understand the protonconduction mechanism in the thin lm.…”

Progress on highly proton-conductive polymer thin films with organized structure and molecularly oriented structure

“…(c) Schematic of multilayer film of poly(N-dodecylacrylamide-co-acrylic acid) by Langmuir-Blodgett method with highly anisotropic proton conduction. Reprinted with permission from Sato et al [13]. Copyright 2015 American Chemical Society.…”

Ionically conducting and photoresponsive liquid crystalline terpolymers: Towards multifunctional polymer electrolytes

“…[22][23][24] Microphase separation between the backbone and the side groups confines the polar groups between smectic layers, resulting in potential anisotropic ionic pathways. [25][26][27] The strong interactions between the sulfonic acid groups, however, disrupt, at least to some extent, the formation of liquid crystalline phases, and restrict the compositional range over which mesogenic behaviour is observed in these materials. 28,29 In the present work, we investigate the effect of including methyl methacrylate, as a third non-mesogenic/non-ionic component, on the structure and conductivity of new side-chain terpolymers containing sulfonic acid and azobenzene units, the poly […”