End‐functionalized thermoplastic‐toughened phthalonitrile composites: influence on cure reaction and mechanical and thermal properties

Phthalonitrile polymers are known for their high thermal stability and good mechanical properties. However, their brittle nature limits their application as structural composites in many critical areas. The present study investigates the feasibility of toughening novolac–phthalonitrile (NPN) resin using chemically modified poly(ether ether ketone) (PEEK). A telechelic PEEK bearing a phthalonitrile end group (PEEKPN) was synthesized via nucleophilic substitution of nitrophthalonitrile with the corresponding phenol–telechelic poly(ether ether ketone) (PEEKOH). Different compositions of NPN and PEEKOH–PEEKPN blends with curing agent, i.e. diaminodiphenylsulfone, were investigated for their cure behaviour and mechanical properties of their carbon fabric composites. In NPN–PEEKOH blends, crosslinking of the phthalonitrile groups was facilitated by phenol‐mediated reactions resulting in the reduction of cure temperatures by around 130 °C with substantial improvement in thermal stability. Blending the resin with the thermoplastic enhanced the mechanical properties of the composites. The apparent flexural strength and impact strength of carbon fabric‐reinforced composites were improved by more than 200 and 150%, respectively, on incorporation of 20 wt% PEEKOH in the NPN matrix. However, higher concentration of PEEKOH had a detrimental effect on the properties. Substitution of phenol end groups by phthalonitrile moieties led to integration of the PEEK moieties with the NPN matrix. However, it was not as conducive as PEEKOH for improving the matrix properties. The better performance of PEEKOH is attributed to the formation of polar heterocyclic groups like isoindoline by way of the phenol–nitrile reaction. © 2014 Society of Chemical Industry     

Influence of Barium Titanate on poly(vinyl pyrrolidone)‐based composite polymer blend electrolytes for lithium battery applications

Nanocomposite polymer blend electrolytes based on poly (ethylene oxide), poly (vinyl pyrrolidone) that contained lithium perchlorate as a dopant, propylene carbonate (PC) as a plasticizer and Barium Titanate (BaTiO₃) as a filler were prepared for various concentrations of BaTiO₃ using solvent casting technique. The structural and complex formations of the composite electrolyte membranes were confirmed by X‐ray diffraction and FTIR analysis. The addition of BaTiO₃ nanofillers improved the ionic conductivity of the polymer electrolytes to some extent when the content of the BaTiO₃ is 10 wt%. The addition of BaTiO₃ also enhanced the thermal stability of the electrolyte. The surface morphology of the sample having a maximum ionic conductivity was studied by AFM. Molecular motion in the polymeric media was supported by fluorescence studies. The charge transfer arises between the polymer blend and Li‐ions were confirmed by UV‐Vis analysis. POLYM. COMPOS., 36:302–311, 2015. © 2014 Society of Plastics Engineers     

Preparation and characterization of silica-supported, group IB–Pd bimetallic catalysts prepared by electroless deposition methods

Electroless deposition has been used to synthesize a series of Au–, Ag–, and Cu–Pd/SiO₂ bimetallic catalysts having incremental surface coverages and compositions of each group IB metal. Thermodynamically unstable, yet kinetically stable, electroless bath(s) were developed using metal bis-cyano salts of the group 1B metal and N₂H₄ (for Au and Ag) or DMAB (for Cu) as reducing agents. The times (1–2 h) and profiles (1st order in group 1B metal concentration) observed for complete deposition indicate good kinetic control of the electroless deposition process. The bimetallic catalysts have been characterized using selective chemisorption, atomic absorption spectroscopy (AAS), Fourier transform infrared spectroscopy (FTIR) of adsorbed CO, and X-ray photoelectron spectroscopy (XPS) techniques. Decreases in Pd surface sites with addition of IB metals confirm deposition onto the supported Pd nanoparticle surfaces. FTIR studies suggest that deposition of Cu and Ag are selective towards Pd(1 1 1) sites, while Au deposits non-discriminately on all Pd sites. Finally, XPS measurements for each family of bimetallic catalysts suggest a net electron transfer from the Pd to the deposited metal.     

Melt rheological behavior of intimately mixed short sisal–glass hybrid fiber‐reinforced low‐density polyethylene composites. I. Untreated fibers

The melt rheological behavior of intimately mixed short sisal–glass hybrid fiber‐reinforced low‐density polyethylene composites was studied with an Instron capillary rheometer. The variation of melt viscosity with shear rate and shear stress at different temperatures was studied. The effect of relative composition of component fibers on the overall rheological behavior also was examined. A temperature range of 130 to 150°C and shear rate of 16.4 to 5470 s^?1 were chosen for the analysis. The melt viscosity of the hybrid composite increased with increase in the volume fraction of glass fibers and reached a maximum for the composite containing glass fiber alone. Also, experimental viscosity values of hybrid composites were in good agreement with the theoretical values calculated using the additive rule of hybrid mixtures, except at low volume fractions of glass fibers. Master curves were plotted by superpositioning shear stress and temperature results. The breakage of fibers during the extrusion process, estimated by optical microscopy, was higher for glass fiber than sisal fiber. The surface morphology of the extrudates was analyzed by optical and scanning electron microscopy. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 432–442, 2003     

Modification of electrodes with nanostructured functionalized thiadiazole polymer film and its application to the determination of ascorbic acid

We report the electropolymerization of 2-amino-1,3,4-thiadiazole (ATD) on glassy carbon (GC) and indium tin oxide (ITO) electrodes in 0.10 M H₂SO₄. The electropolymerized ATD (p-ATD) film was characterized by cyclic voltammetry, attenuated total reflectance (ATR)-FT-IR spectroscopy, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The AFM image showed that the p-ATD formed a spherical-like structure with a thickness of 25 nm. XPS of the p-ATD film showed binding energies at 398.7, 400.3 and 401.3 eV in the N 1s region corresponding to –N, –NH– and –N⁺H–, respectively, and at 285.5 and 287.0 eV in the C 1s region corresponding to C–N and CN, respectively. The appearance of binding energies at 285.5 and 287.0 eV confirmed that the p-ATD film proceeded via C–N and CN linkages and not via C–C or CC linkages. The p-ATD film deposited on the GC electrode was successfully used for the determination of ascorbic acid (AA) at physiological pH. The amperometric current was increased linearly from 7.5 × 10⁻⁸ to 2.0 × 10⁻⁵, and the detection limit was found to be 0.28 nM (S/N = 3).     

Polystyrene supported pyrazolinium Cr(VI) reagents: preparation and use in synthetic organic chemistry

Divinylbenzene (DVB) and ethyleneglycol dimethacrylate (EGDMA) crosslinked polystyrenes (2%) were functionalized to generate pyrazolinium chromate, chlorochromate and pyrazole–CrO₃ complex functionalities. These were found to oxidize primary and secondary alcohols to the corresponding carbonyl compounds in high yields. The influence of solvent, temperature, catalyst and molar excess of the reagent in these oxidation reactions was investigated to find out the optimum conditions for effective oxidation reactions. EGDMA crosslinked polystyrene supported reagents showed higher reactivity in terms of functional group capacity and percentage yield. Also, chlorochromate reagent was found to be very efficient in oxidizing alcohols to carbonyl compounds. The spent polymeric reagent after the oxidation step can be easily removed by filtration and can be regenerated many times. © 1998 SCI.     

Copper (II) and silver (II) complexes of polymer-bound porphyrins with Schiff base linkage

Two percent divinylbenzene (DVB)–crosslinked polystyrene was prepared and functionalized to obtain its aldehyde analog. Amino porphyrins were anchored on this polymer support by Schiff base condensation. The anchoring positions were adjusted so as to obtain ortho-, meta-, and para-isomeric systems. The polymer-bound free-base porphyrins were metallated to obtain the corresponding Cu(II) and Ag(II) complexes by treating them with the corresponding metal salt solutions. The products were characterized chemically and spectroscopically. Electronic and ESR spectral analysis shows the microenvironmental participation of the polymer network on the electronic levels of the porphyrin system. The extents of steric and electronic participation were evaluated and are presented. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 89–93, 1998     

Studies on semiinterpenetrating polymer networks based on poly(vinyl chloride-co-vinyl acetate) and poly(alkyl methacrylates)

A number of semi-interpenetrating polymer networks (IPNs) based on linear poly(vinyl chloride-co-vinyl acetate) and poly(alkyl methacrylates) were synthesized. The semi-IPNs were found to be transparent, high strength materials. The IPNs show only one glass-transition temperature and it is dependent on the composition as studied by differential scanning calorimetry and dynamic mechanical analysis. These IPNs are also characterized by high tan δ values. The tensile strength of the IPNs were found to be higher compared to the starting polymers. In order to compare the properties of these IPNs with the corresponding homopolymers and blends, the latter were synthesized and the properties were studied. © 1994 John Wiley & Sons, Inc.     

Studies on interpenetrating polymer networks based on nitrile rubber-poly(vinyl chloride) blends and poly(alkyl methacrylates)

Several interpenetrating polymer networks (IPNs) based on nitrile rubber-poly(vinyl chloride) blends and various alkyl methacrylates have been synthesized. The rubber blends were swollen in methacrylate monomers containing required amounts of initiator and crosslinker for specific time periods and then polymerized at higher temperature. The composition of the IPNs could be varied by changing the swelling time. The IPNs were characterized for their glass-transition temperature, dynamic mechanical properties, and tensile properties. The effect of structure and composition on the vibration damping characteristics of these IPNs are discussed. © 1994 John Wiley & Sons, Inc.