Susanta Banerjee

Solubility improvements in aromatic polyimides by macromolecular engineering

Polyimides are proved to be an important class of polymers due to their outstanding set of physical and chemical properties. However, this class of polymers suffers from poor processability, which limits their scope of application. This review article deals with approaches that have been undertaken by different researchers to improve the processability of this class of polymers. Mostly, these are synthetic approaches using new diamine and dianhydride monomers that reduce the interchain interaction of the final poyimide by flexibilizing the polymer chain or increasing the fraction free volume. Accordingly, the structural factors that are responsible for better processability are discussed and representative diamine and diahydride structures are tabulated under different categories. Major efforts towards development of soluble polyimides but maintaining excellent mechanical and thermal properties have been done by our group and are also covered in this article.

Poly‐Schiff bases. III. Synthesis and characterization of polyesterazomethines

Ten new polyesterazomethines have been synthesized by solution polycondensation of five different diamines with 4,4′-[terephthaloyloxy]bis-3-ethoxybenzaldehyde and 4,4′-[isophthaloyloxy]bis-3-ethoxybenzaldehyde using dimethylacetamide in the presence of anhydrous LiCL. Fibrous polymers were precipitated by pouring the solutions into water. The polymerization proceeds rapidly to give highly viscous solutions. The resulting polymers were characterized by viscosity measurement, IR, x-ray diffraction study, elemental analysis, and DSC study. 1H-NMR spectra of some of the polymers were also recorded. The thermal stability of the polymers was evaluated by TGA and IGA study. Electronic spectra of the polymers were recorded in H2SO4.

Cross-linked sulfonated poly(ether imide)/silica organic–inorganic hybrid materials: proton exchange membrane properties

A series of sulfonated poly(ether imide)–silica hybrid membranes (SPI/S-X) were prepared from fluorine-containing ter-copolyimide and ∼15 nm colloidal silica particles. The soluble poly(ether imide) with carboxylic acid pendant groups was synthesized by one pot high temperature polycondensation reaction using a sulfonated diamine, 4,4′-diaminostilbene-2,2′-disulfonic acid (DSDSA), fluorinated quadri diamine (QA), 3,5-diaminobenzoic acid (DABA) and 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA). Such pendant carboxylic acid groups undergo condensation reaction with colloidal silica to provide organic–inorganic bonding that effectively improves the compatibility of nanocomposite membranes. The structure of the synthesized polymer was analysed by FT-IR and 1H NMR spectroscopy. The esterification reaction was carried out between colloidal silica particles (with different loading) and the carboxylic acid containing polymer chains by thermal treatment in the presence of p-toluenesulfonic acid (PTSA), which catalysed the esterification reaction. The prepared hybrid membranes exhibited excellent thermal and oxidative stability. The mechanical properties of the membranes were enhanced with a certain wt% of silica loading whereas the swelling ratio and oxygen permeability of the membranes were reduced by cross-linking. The microstructure of the resulting hybrid membranes were extensively investigated by SEM and TEM. Good compatibility and uniform distribution of the silica nanoparticles in the hybrid membrane was observed by SEM. An excellent nano-phase separated structure was observed under TEM which indicated the formation of well-dispersed hydrophilic domains throughout the membrane. The hybrid membranes showed significantly high proton conductivity in water medium which is in the range of commercially available Nafion® membranes under similar experimental conditions.

High Tg, processable fluorinated polyimides containing benzoisoindoledione unit and evaluation of their gas transport properties

This article describes the preparation of a series of processable fluorinated poly(ether imide)s from a new diamine monomer 4,9-bis-[4-(4′-amino-3-trifluoromethyl-biphenyl-4-yloxy)-phenyl]-2-phenyl-benzo[f]-isoindole-1,3-dione. The polymers showed extremely high Tg (up to 335 °C), outstanding thermal stability (up to 559 °C) and high tensile strength (up to 102 MPa). The transparent (λcut-off ≥ 363 nm) membranes from these polymers were investigated for their gas transport properties for CO2, O2, N2 and CH4 at three different temperatures. The effect of the benzo[f]isoindole-1,3-dione moiety and the aromatic dianhydrides (BPADA, 6FDA, BTDA, ODPA and PMDA) towards the glass transition temperatures of the polymers and their consequences on gas transport properties have been investigated. The polymer prepared from 6FDA showed the highest permeability coefficient for all the gases (PCO2 = 71.3, PO2 = 25.4) whereas BPADA based polymer exhibited the highest permselectivity (CO2/CH4 ∼ 37.2 and O2/N2 ∼ 8.4), staying closer to the latest upper boundary limit drawn by L. M. Robeson.

A simplistic approach to green future with eco-friendly luminescent carbon dots and their application to fluorescent nano-sensor ‘turn-off’ probe for selective sensing of copper ions

Zero-dimensional fluorescent nanoparticles having specificity as molecular probe appears to be strategically balanced fluorescent nano-probes. In this work, purified lemon extract and l-arginine have been thermally coupled for the extremely acute detection of Cu2+ in aqueous medium. The Cu2+ ions may be captured by the amino groups on the surface of the nano-sensor to form cupric ammine complex resulting in quenched fluorescence via an inner filter effect. Our proposed nano-probe is N-doped carbon dots (NCDs) which are efficiently selective as fluorescent chemosensor due to enormous binding affinity towards Cu2+ in a wide range of concentration (0.05-300μM) within a few minutes.

Poly-Schiff bases. V. Synthesis and characterization of novel soluble fluorine-containing polyether azomethines

A new dialdehyde monomer, 4,4′-(hexafluoroisopropylidine) bis(p-phenoxy) benzaldehyde, was prepared; it led to a number of novel poly-Schiff bases in reactions with different diamines, such as 4,4′-diaminidiphenyl ether, 4,4′-(isopropylidine) bis(p-phenoxy) dianiline, 4,4′-(hexafluoroisopropylidine) bis(p-phenoxy) dianiline, and benzidine. The polymers were characterized with viscosity measurements, nitrogen analyses, and IR and 1H NMR spectroscopy. These poly-Schiff bases showed good thermal stability up to 491 °C for 10% weight loss in thermogravimetric analysis under air and high glass-transition temperatures up to 215 °C in differential scanning calorimetry. These polymers were soluble in a wide range of organic solvents, such as CHCl3, dimethylformamide (DMF), dimethyl sulfoxide, and 1-methyl-2-pyrrolidon (NMP), and were insoluble in toluene and acetone. Thin films of these polymers cast from DMF exhibited tensile strengths up to 38 MPa.

Synthesis, characterization and gas transport properties of cardo bis(phenylphenyl)fluorene based semifluorinated poly(ether amide)s

Here we report the synthesis and properties of a series of processable poly(ether amide)s (PAs) having the bis(phenylphenyl)fluorene moiety prepared from a new diamine monomer, 9,9-bis-[3-phenyl-4-{2′-trifluoromethyl-4′-(4′′-aminophenyl) phenoxy}phenyl]fluorene. Analogous PAs having the bis(phenyl)fluorene moiety have also been prepared from the diamine 9,9-bis-[4-{2′-trifluoromethyl-4′-(4′′-aminophenyl) phenoxy} phenyl]fluorene for comparative purposes. The synthesized PAs exhibited high thermal stability (up to 517 °C and 539 °C in air and nitrogen respectively, for 10% weight loss), high glass transition temperature (272–299 °C) and high tensile strength up to 117 MPa. The optically transparent membranes (λcut-off ≥ 368 nm) from these PAs showed high gas permeability in barrer (PCO2 up to 67.42 and PO2 up to 15) and high permselectivity (PCO2/PCH4 up to 88.37 and PO2/PN2 up to 10.84); especially for the O2/N2 gas pair the PAs surpass or touch the present upper boundary limit of 2008 drawn by Robeson. The effect of the bis(phenylphenyl)fluorene moiety and diacid moieties in PAs on the dielectric values, thermal, mechanical, optical and gas transport properties were correlated.

Study of diffusion and sorption of bis-(2-chloroethyl)sulfide (SM) and bis-(2-chloroethyl)ether (OM) through polypropylene (PP) and biaxial-oriented polypropylene (BOPP) films by the FTIR-ATR spectroscopic method

The diffusion of sulfur mustard (SM) and oxygen mustard (OM) in polypropylene (PP) and biaxial-oriented PP (BOPP) was measured using Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy, which allows one to study the diffusion of liquid through thin polymer films in situ. The temperature-dependent diffusion coefficients of OM and SM for PP and BOPP are also reported ; these are in good agreement with the values obtained by the weight gain method. The activation energy of diffusion is determined by both methods. The polymer-penetrant interaction parameter (K) and transport number (n) are calculated for the system PP/OM and BOPP/OM by weight gain method. The n values indicate a Fickian mode of diffusion.

The reaction of thiodiglycol on metal-impregnated carbon

Abstract In order to investigate the reactive removal of persistent chemical warfare (CW) gases, active carbons, grade 80 CTC, and active carbon impregnated with cobalt(II), chromium(VI), nickel (II), cadmium(II) or copper(II) salts were saturated at room temperature with the vapours of thiodiglycol (TDG), a hydrolysis product of sulphur mustard. The carbons exposed to TDG were subjected to thermogravimetric analysis (TGA). The thermograms indicated the reactions of metal salts with the adsorbate, as was confirmed by GC-MS after extracting the reaction products from TDG-exposed carbon impregnated with a mixture of chromium(VI) salt and sodium hydroxide. The extractants used were dichloromethane and methanol. 1,4-Oxathiane and 1,4-oxathiane,4-oxide were the reaction products on Cr(VI) plus NaOH impregnated carbon.The reaction mechanisms are also proposed.

Proton exchange properties of flexible diamine-based new fluorinated sulfonated polyimides

A series of new semifluorinated sulfonated polyimide copolymers (DHNHXX) were prepared from 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA), 4,4′-diaminostilbene-2,2′-disulfonic acid (DSDSA) and 1,4-bis-[{2′-trifluoromethyl-4′-(4′′-aminophenyl)phenoxy}] benzene (HQA). The degree of sulfonation of DHNHXX was varied by changing the molar ratio of the sulfonated diamine, DSDSA to the non-sulfonated diamine, HQA. The flexible DHNHXX membranes showed high thermal stability (desulfonation temperature above 270 °C) and good mechanical properties. The oxidative stability of DHNHXX improved with increasing the fluorine content. DHNHXX showed anisotropic dimensional changes, and good water stability (did not dissolve for up to 415 h), higher than many other sulfonated polyimides. Transmission electron microscopy (TEM) analysis revealed cluster-like microstructures for the DHNHXX membranes, suggesting good phase-separated morphology. DHNH70 with IEC = 2.10 meq. g−1 exhibited high proton conductivity, with a maximum up to 129 mS cm−1 at 90 °C in water.