Soma Banerjee

Aluminum-substituted phosphotungstic acid/sulfonated poly ether ether ketone nanocomposite membrane with reduced leaching and improved proton conductivity

Aluminum-substituted tungstophosphoric acid (AlTPA)/sulfonated poly ether ether ketone (SPEEK) (sulfonation degree approximately 77%) nanocomposite membranes have been prepared for fuel cell application. AlTPA nanoparticles are synthesized by the reaction of TPA and aluminum nitrate in aqueous medium. X-ray diffraction, energy dispersive X-ray, Fourier transform infrared and Raman spectroscopies, and field-emission scanning electron microscopy (FESEM) are used to characterize the AlTPA particles and SPEEK. Study reveals that 2.31 numbers of protons of TPA have been replaced by Al3+ in AlTPA with retention of Keggin’s structure. Nanocomposite membranes with varying AlTPA and TPA content are prepared and evaluated by measuring water uptake, ion exchange capacity, equilibrium water content, water desorption rate, proton conductivity, leaching tendency, and thermal properties. SPEEK/AlTPA nanocomposite membrane exhibits proton conductivity as high as 1.09 mS cm−1 at 10 wt% filler loading. Leaching of filler is reduced by approximately 92% in SPEEK/AlTPA nanocomposite membrane compared to SPEEK/TPA membrane. SPEEK/AlTPA membrane shows approximately 15% higher equilibrium water content and approximately 57% reduction in water desorption rate as compared to SPEEK/TPA membrane. Membranes are thermally stable up to 215°C, which is well above the operating temperature of fuel cells. Composite films are also examined by FESEM to gain further insights into the microstructure.

Synthesis of polyether ether ketone membrane with pendent phosphonic acid group and determination of proton conductivity and thermal stability

Incorporation of phosphonic acid groups in the polymer backbone by direct phosphonation or by polymerization of prefunctionalized monomers requires harsh reaction conditions. The present research work reported an easy synthesis strategy of phosphonic acid-containing diphosphonated polyether ether ketone (P-PEEK) by polycondensation of difluoro benzophenone and phosphonated bisphenol A (BPA). Phosphonation of BPA was carried out by monophosphoazylation followed by rearrangement in the presence of organolithium compound at −78°C. Nuclear magnetic resonance (NMR) imaging, Fourier transform infrared, and electrospray ionization mass spectrometry were performed to acquire complete structural information about the synthesized monomer and polymer. Degree of phosphonation of the synthesized polymer calculated from proton NMR spectra was as high as 70%. Thermal properties of the P-PEEK were checked using a differential scanning calorimeter (DSC) and a thermogravimetric analyzer. Moderate increase in melting point and glass transition temperature (T g) were observed from the DSC analysis. Solubility of the polymer was improved significantly in the common organic solvents that permitted the polymer to be solution casted. Solid electrolyte membrane exhibited through plane proton conductivity of 7.5 × 10−5 S cm−1 at 25°C under fully hydrated conditions.

Nanocomposites Based on Carbon Nanomaterials and Electronically Nonconducting Polymers

Polymer nanocomposites (PNCs) are the growing field of research having significant contribution in limitless application areas due to excellent combinations of tunable properties. Carbon-based PNCs are of recent research interest and cover numerous fields of applications including structural composites, drug delivery, shape memory polymers, etc. In this chapter, different allotropes of carbon, viz., carbon nanotubes, graphene, graphene oxide, fullerenes, metallofullerenes, carbon nanohorn, carbon nanodiamond, etc., are discussed in brief. Different types of polymeric materials used for the fabrication of PNCs are also introduced. Several types of carbon-based PNCs and their fabrication methodologies have been emphasized to represent a broad overview on carbon-based PNCs of nonconducting polymer matrices.