Sulfonated Polyimide Membranes Constructed by Main-Chain and Molecular-Network Engineering Strategy for Direct Methanol Fuel Cell

Excessive swelling is one important factor that leads to high fuel permeability and limited operating concentration of methanol for proton exchange membranes. Herein, a collaborative strategy of main-chain and molecular-network engineering is applied to lower swelling ratio and improve methanol resistance for highly sulfonated polyimide. Two m-phenylenediamine monomers (4-(2,3,5,6-tetrafluoro-4-vinylphenoxy)benzene-1,3-diamine and 4,6-bis(2,3,5,6-tetrafluoro-4-vinylphenoxy)benzene-1,3-diamine) with tetrafluorostyrol groups are designed and synthesized. Two series of cross-linked sulfonated polyimides (CSPI-Ts, CSPI-Bs) are prepared from the two diamines, 4,4'-diaminostilbene-2,2'-disulfonic acid and 1,4,5,8-naphthalenetetracarboxylicdianhydride. The rigid main-chain structure is cornerstone for wet CSPI-Ts and CSPI-Bs remaining stable at elevated temperatures. The introduction of hydrophobic cross-linked network further improves their dimensional stability and methanol resistance. CSPI-Ts and CSPI-Bs show obviously improved performances containing high proton conductivity (121 ± 0.27-158 ± 0.35 S cm-1 ), low swelling ratio (9.6 ± 0.40%-16.1 ± 0.01%) and methanol permeability (4.14-7.69 × 10-7 cm2 s-1 ) at 80 °C. The direct methanol fuel cell (DMFC) is assembled from CSPI-T-10 with balanced properties, and it exhibits high maximum power density (PDmax ) of 82.3 and 72.6 mW cm-2 in 2 and 10 m methanol solution, respectively. The ratio of PDmax in 10 m methanol solution to the value in 2 m methanol solution is as high as 88%. The CSPI-T-10 is promising proton exchange membrane candidate for DMFC application.

Naphthalene diimides: perspectives and promise

In this review, we describe the developments in the field of naphthalene diimides (NDIs) from 2016 to the presentday. NDIs are shown to be an increasingly interesting class of molecules due to their electronic properties, large electron deficient aromatic cores and tendency to self-assemble into functional structures. Almost all NDIs possess high electron affinity, good charge carrier mobility, and excellent thermal and oxidative stability, making them promising candidates for applications in organic electronics, photovoltaic devices, and flexible displays. NDIs have also been extensively studied due to their potential real-world uses across a wide variety of applications including supramolecular chemistry, sensing, host-guest complexes for molecular switching devices, such as catenanes and rotaxanes, ion-channels, catalysis, and medicine and as non-fullerene accepters in solar cells. In recent years, NDI research with respect to supramolecular assemblies and mechanoluminescent properties has also gained considerable traction. Thus, this review will assist a wide range of readers and researchers including chemists, physicists, biologists, medicinal chemists and materials scientists in understanding the scope for development and applicability of NDI dyes in their respective fields through a discussion of the main properties of NDI derivatives and of the status of emerging applications.

Synthesis and Characterization of Highly Proton Conducting Sulfonated Polytriazoles

This article describes the synthesis and characterization of highly sulfonated polytriazole copolymers (PTSQSH-I to IV) with IEC_w values ranging from 2.41 to 3.49 mequiv g^-1. The copolymers were synthesized by click reaction between equimolar amount of a dialkyne monomer, potassium 2,5-bis(2-propyn-1-yloxy)benzenesulfonate, and a mixture of two different diazide monomers, 4,4-bis[3'-trifluoromethyl-4'(4-azidobenzoxy)benzyl]biphenyl and 4,4'-diazido-2,2'-stilbene disulfonic acid disodium salt. The copolymers were characterized by Fourier transform infrared and NMR spectroscopy techniques. The membranes were prepared by dissolving the salt form of the copolymers in dimethyl sulfoxide. The copolymers showed high thermal, mechanical, and oxidative stabilities, and the acidified membranes showed very high proton conductivity (43-173 and 132-304 mS cm^-1 at 30 and 80 °C, respectively). Transmission electron microscopy images confirmed the formation of well-phase-separated morphology with interconnected hydrophilic domains (20-150 nm).