High Proton Conduction of Organized Sulfonated Polyimide Thin Films with Planar and Bent Backbones

Abstract

Fast proton conduction was achieved in organized lamellar structures with in-plane oriented structure parallel to the substrate surface using a lyotropic liquid-crystalline (LC) property. Alkyl sulfonated polyimides (ASPIs) with bent main chain structure were newly synthesized to investigate relations between the higher order structure and proton transport properties. Proton conductivity of all polyimide thin films was greater than 10–2 S/cm. Grazing-incidence small-angle X-ray scattering (GI-SAXS) revealed that both planar and bent ASPI thin films exhibited humidity-induced lyotropic lamellar structure. Infrared p-polarized multiple-angle incidence resolution (pMAIR) studies revealed that main chain backbones of both planar and bent ASPI thin films show an in-plane orientation parallel to the substrate surface. Results demonstrate that sulfonated alkyl side chains contribute strongly to the lyotropic LC property, which enhances molecular orderings and proton conductivity by water uptake. This study extends knowledge of the molecular design for highly proton conductive polymers with humidity-induced lyotropic LC property.

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

“…Recently, Ono and co-workers discussed the influence of rigidity and planarity of the main chain structure in ASPI thin films (Figure 5(d)) [101]. Earlier studies showed interchain packing for the lamellar structure as suppressed by steric effects of nonplanar and bent backbones of polyimides without sulfonic acid group [102].…”

“…ASPI thin film with high molecular weight exhibited higher molecular order and higher proton conductivity than that with low molecular weight. (d) Schematic of influence of rigidness and planarity of the main chain to the organized structure in ASPI thin films Proton conductivity with planar backbone was higher than that with bent backbone [101]. Reprinted with permission from Ono et al [101].…”

“…(d) Schematic of influence of rigidness and planarity of the main chain to the organized structure in ASPI thin films Proton conductivity with planar backbone was higher than that with bent backbone [101]. Reprinted with permission from Ono et al [101]. Copyright 2018 American Chemical Society.…”

Understanding of Nanophase Separation and Hydrophilic Morphology in Nafion and SPEEK Membranes: A Combined Experimental and Theoretical Studies

“…However, they are limited by their low operation temperature, high cost, and high fuel crossover [9,10,11]. To address the problems, sulfonated nonfluoroniated aromatic materials, such as poly(phenylene)s [12,13], polyphenylenes [14], polyimides [15], poly (arylene ether sulfone) [16,17], and poly (ether ether ketone) (SPEEK) [18] have been proposed with good chemical/thermal stability, low cost, and high mechanical stability. However, poor hydrophilic/hydrophobic phase separation and insufficient proton conductivity were reported [19,20,21].…”

Sulfonated poly (arylene ether sulfone)-graft-sulfonated poly (vinyl alcohol) proton exchange membranes: Improved proton selectivity

“…6,7 Recently, aromatic hydrocarbon membranes have been developed for their low methanol permeability, excellent mechanical properties and low cost. 8,9 Typical representatives including sulfonated polyimide (SPI), [10][11][12][13] sulfonated poly (arylene ether ketone) (SPEEK). [14][15][16] sulfonated poly (arylene ether sulfone) (SPAES) [17][18][19][20] and sulfonated polybenzimidazole 21,22 are used as PEM.…”