Proton-Conducting Hydrogen-Bonded 3D Frameworks of Imidazo-Pyridine-Based Coordination Complexes Containing Naphthalene Disulfonates in Rhomboid Channels.

Coordination complexes of an olefinic molecule (PIP) containing pyridine and imidazopyridine moieties with ZnII /NiII metal salts were shown to exhibit appreciable proton conductivity. These complexes form 3D-hydrogen bonded frameworks containing rhomboidal channels that are occupied by uncoordinated 1,5-naphthalenedisulfonate (NDS). The extensive hydrogen bonding between the frameworks and NDS resulted in thermally stable and water-insoluble materials. Irrespective of the metal atom present, both complexes exhibited moderate to high proton conduction in the range of 10-5 to 0.5×10-3  S cm-1 depending on the temperature and humidity levels.

Novel Sulfonated Co-poly(ether imide)s Containing Trifluoromethyl, Fluorenyl and Hydroxyl Groups for Enhanced Proton Exchange Membrane Properties: Application in Microbial Fuel Cell.

A hydroxyl group containing new cardo diamine monomer was synthesized, namely 9,9-bis (hydroxy- (4'-amino(3-trifluoromethyl)biphenyl-4-oxy)-phenyl)-9H-fluorene (mixture of isomers, HAPHPF). HAPHPF, along with a sulfonated diamine monomer, 4,4'-diaminostilbene-2,2'-disulfonic acid (DSDSA), was used to prepare a series of new sulfonated copolyimides by polycondensation with 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA). The degree of sulfonation (DS < 1) was adjusted by the feed ratio of DSDSA/HAPHPF and the copolymers were named as DHN-XX, where XX denotes the mole percentage of DSDSA (XX = 50, 60, and 70). The copolymers showed high molecular weights. The copolymer structure and composition were confirmed by FTIR and NMR techniques. Copolymer membranes were prepared through solution cast route by using dimethyl sulfoxide as a solvent. The membranes showed high thermal, mechanical, hydrolytic and peroxide radical stability, and low water uptake and low swelling ratios. Well-separated hydrophilic and hydrophobic phase morphology was observed in TEM and AFM images of the copolymer membranes and was further supported by the SAXS studies. The proton conductivity of the DHN-70 was as high as 97 mS cm-1 at 80 °C and the value is significantly higher than that of the nonhydroxylated analogue. The membranes also showed superior microbial fuel cell (MFC) performance, similar like Nafion 117 under similar test conditions. The chemical oxygen demand removal values provide substantial evidence that the fabricated membranes can be utilized in bioelectrochemical systems.

Polyimides Containing Phosphaphenanthrene Skeleton: Gas-Transport Properties and Molecular Dynamics Simulations.

A series of new semifluorinated polyimide (PI) films with phosphaphenanthrene skeleton were prepared by thermal imidization of poly(amic acid)s derived from a diamine monomer: 1,1-bis[2'-trifluoromethyl-4'-(4″-aminophenyl)phenoxy]-1-(6-oxido-6H-dibenz⟨c,e⟩⟨1,2⟩oxaphosphorin-6-yl)ethane on reaction with four structurally different aromatic dianhydrides. The chemical structures of the polymers were established by Fourier transform infrared and 1H NMR spectroscopy techniques. The polymers showed a good combination of thermal and mechanical properties (T d10 up to 416 °C under synthetic air and tensile strength up to 91 MPa), low dielectric constant (2.10-2.55 at 1 MHz), and T g values as high as 261 °C. Gas permeabilities of these films were investigated for four different gases CO2, O2, N2, and CH4. The PI films showed high gas permeability (P CO2 up to 175 and P O2 up to 64 barrer) with high permselectivity (P CO2 /P CH4 up to 51 and P O2 /P N2 up to 7.1), and the values are better than those of many other similar polymers reported earlier. For the O2/N2 gas pair, the PIs (PI A) surpassed the present upper boundary limit drawn by Robeson. A detailed molecular dynamics (MD) simulation study has been conducted to understand better the gas-transport properties. The effect of phosphaphenanthrene skeleton, its spatial arrangement, and size distribution function of the free volume were studied using molecular dynamics (MD) simulation and the results are correlated with the experimental data.