Functional properties of microwave‐absorbent nanocomposite coatings based on thermoplastic polyurethane‐based and hybrid carbon‐based nanofillers

This paper describes the effect of nanofillers, such as nanographite, nickel–zinc ferrite (NiZnFerrite), and in‐house developed hybrid nanographite particles (i.e. iron‐coated nanographite [FeNG] and iron–nickel co‐deposited nanographite [FeNiNG] particles), on microwave‐absorption properties of thermoplastic polyurethane (TPU) based nanocomposite coatings on textile substrate. The flexible coatings were tested for various functional properties such as microwave absorbency, gas barrier property, impedance, and weather resistance. The comparison has also been made with other fillers such as bulk graphite (G) and iron powder (Fe) and carbon nanofiber (CNF) in coating form. The nanoparticles' dispersion was observed through optical microscope and phase image analysis on atomic force microscopy. The impedance behavior of such coated samples with 10 wt% nanofillers is frequency dependent except for CNF, which shows frequency‐independent behavior even at 2 wt% loading. The gas barrier property of the FeNG‐based and FeNiNG‐based coatings is better than that of pure TPU; however, G‐based, NG‐based, and NiZnFerrite‐based coatings show excellent barrier property. The coatings were evaluated for their microwave absorbency at low‐frequency (from 0.3 to 1.5 GHz) as well as high‐frequency (8–18 GHz) ranges. The FeNG‐based and FeNiNG‐based nanocomposite coatings showed good absorbency over a frequency range of 8 to 14 GHz as compared with those of others. The flexibility of the nanocomposite films is almost retained even at 10 wt% nanofiller loading. The weather resistance of the films was also evaluated, and the FeNiNG‐based coating outperformed the FeNG‐based coating as the latter is prone to oxidation on exposure to environment. Copyright © 2011 John Wiley & Sons, Ltd.     

Polyisobutylene‐based biomaterials

This article highlights the biomaterial‐related research of the Macromolecular Engineering Research Centre (MERC). The MERC group concentrated on polyisobutylene (PIB)‐based biomaterials. In this article, first the unique properties of PIB are discussed, followed by a review of PIB‐based potential biomaterials. MERC's systematic research program aimed to develop novel PIB‐based biomaterials is then highlighted, including surface modification and biocompatibility studies. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3091–3109, 2004     

Elastomer based tunable optofluidic devices

The synergetic integration of photonics and microfluidics has enabled a wide range of optofluidic devices that can be tuned based on various physical mechanisms. One such tuning mechanism can be realized based on the elasticity of polydimethylsiloxane (PDMS). The mechanical tuning of these optofluidic devices was achieved by modifying the geometry of the device upon applying internal or external forces. External or internal forces can deform the elastomeric components that in turn can alter the optical properties of the device or directly induce flow. In this review, we discuss recent progress in tunable optofluidic devices, where tunability is enabled by the elasticity of the construction material. Different subtypes of such tuning methods will be summarized, namely tuning based on bulk or membrane deformations, and pneumatic actuation.     

Hg-selective fluorogenic chemodosimeter based on naphthoflavone

A new Hg²⁺-selective chemodosimeter based on α-naphthoflavone was investigated. The chemodosimetric behavior is based on the Hg²⁺-triggered desulfurization of flavothione into its oxygen analogue flavone. The signaling was effective in aqueous environment and the selective signaling was not affected in the presence of common physiologically and environmentally important metal ions.     

Modelling carbon nanotube based biosensor

This paper presents a two-dimensional-in-space mathematical model of an amperometric biosensor based on an enzyme-loaded carbon nanotubes layer deposited on a perforated membrane. The developed model is based on non-linear non-stationary reaction-diffusion equations. By changing input parameters the output results are numerically analysed with a special emphasis to the influence of the geometry and the catalytic activity of the biosensor to its response. The numerical simulation at transition and steady state conditions was carried out using the finite difference technique. The mathematical model and the numerical solution were validated by experimental data. The obtained agreement between the simulation results and experimental data was admissible at different concentrations of the substrate and the mediator.     

Synthesis of an iminosugar based peptidomimetic analogue

The synthesis of an 1-deoxymannojirimycin based analogue of a known HIV-protease inhibitor is described. The strategies employed for introduction of the pharmacophore groups onto the azasugar scaffold were based on regioselective reactions of the hydroxyl groups of the natural product and of d-fructopyranoside derivatives.     

Amide based receptors for anions

This review article illustrates the contribution of amide based receptors to the development of anion complexing agents. Amides are incorporated into a wide variety of systems that can be divided into two broad categories; organic and inorganic. The first section is separated into cyclic and acyclic systems built on a solely organic framework. The second section is comprised of metal containing systems such as metallocenes, [Ru(bipy)₃]²⁺ based complexes, porphyrins and other metallo-based receptors. Where appropriate, the results of solution binding studies and sensing outputs are summarized.     

Actuator based on MWNT/PVA hydrogels

The first actuator based on multiwalled carbon nanotube (MWNT) hydrogels was developed through simple hydrogelation with poly(vinyl alcohol) (PVA). This actuator exhibited excellent actuating properties compared with the corresponding actuator based on poly(acrylic acid)/PVA hydrogels.     

Optical biosensors based on Prussian Blue films

Optical biosensing schemes based on enzymatically modified inorganic/organic transparent films predominately composed of Prussian Blue are demonstrated. The composite film, which is non-electrochemically deposited on a non-conducting support. is used as an optical transducer for flow-through biosensors based on hydrolases and oxidases. Urease and glucose oxidase are utilized as model enzymes. Action of the urea biosensor is based on optical pH sensitivity of Prussian Blue indicator. The glucose biosensor is acting as first-generation optical biosensor based on in situ generated Prussian White transducer for hydrogen peroxide. These simple, single-pass transmission optical biosensors exhibit sensitivity in the millimolar range of concentration. The biosensors are very stable owing to presence of a poly(pyrrolylbenzoic acid) network in the composite material. This organic polymer plays a dual role as a binding agent for inorganic material and as a functionalized support for strong covalent immobilization of enzyme molecules.     

Hydrogels based on polycarboxylic acid-agar-agar complexes

IR spectroscopy and viscometry data have shown that poly(acrylic acid) and poly(methacrylic acid) form complexes with agar-agar in aqueous solutions as they do with other polysaccharides. The polyacid-agar-agar complexes are typical hydrogels. The swelling index of hydrogels based on the poly(methacrylic acid)-agar-agar complex has been found to be markedly lower than that of poly(acrylic acid)-agaragar complex. The hydrogels based on the complex of cross-linked poly(acrylic acid) with agar-agar can be of practical interest as polymeric carriers for drugs.     

Supramolecular ionic liquid based on graphene oxide

For the purpose of preparing liquefied graphene oxide (GO), a process consisting of sulfonation with sodium sulfanilic acid and ionization with bulky amine-terminated Jeffamine? was designed and performed. The obtained hybrid fluid is actually a supramolecular ionic liquid (SIL) with sulfonated GO as the central anions and the terminal ammonium groups of Jeffamine? as the surrounding cations. The successful grafting of the GO sheets with Jeffamine?via an ionic structure was verified and the morphology of the SIL was characterized. The SIL based on GO (GO-SIL) exhibits excellent solubility and amphiphilicity. The rheological measurements confirm the essential viscoelasticity and the liquid-like behavior of GO-SIL. The present GO based SIL suggests promising applications in the fabrication of various GO or graphene based composite materials. In addition, the new functionalization method may guide the future work on acquiring derivatives with tunable properties by simply changing the bulky canopy.     

Nickel/cobalt based materials for supercapacitors

We briefly summarize the fundamental mechanism of supercapacitors and classify them into three kinds according to the different energy storage mechanism. We further discuss the energy storage mechanism of nickel/cobalt based materials, and we suggest that these kinds of battery-type materials should be classified into hybrid supercapacitor instead of pseudocapacitors.     

Study of cell membrane based coatings in capillary electrochromatography

Neuronal cell line based membrane models were studied as capillary coatings by capillary electrochromatography. The membrane models were based either on membrane suspensions or on membrane lipid extractions. The stability of the coatings at different pH values and buffer compositions was studied. The results showed that the cell membrane suspension based coatings were stable over pH range of 6.5–10.8. The use of Hepes instead of TE buffer did not improve the coating performance.     

Preparation of mesoporous molecular sieve based hydrocracking catalysts

A series of hydrocracking catalysts based on mesoporous molecular sieves MCM-41 and SBA-15 with different silica to alumina ratios was prepared. Nickel and molybdenum were used as active metals to impregnate the extrudates prepared by using molecular sieves. The catalysts were characterized for physical and chemical properties and evaluated for the hydrocraking of desulfurised vacuum gas oil. The conversion of DS-VGO was lower as compared to that of the catalyst based on USY zeolite. However, the gas yield was lower in case of mesoporous materials based catalysts.     

Biocomposites based on Alfa fibers and starch‐based biopolymer

Biocomposite materials based on Alfa cellulose fibers (esparto grass plant) as reinforcing element and starch‐based biopolymer matrix were prepared and characterized in terms of mechanical performance, thermal properties, and water absorbance behavior. The fibers and the matrix were first mixed in the melted state under mechanical shearing using a plastograph and the obtained composites were molded by injection process. The tensile mechanical analysis showed a linear increase of the composite flexural and tensile modulus upon increasing the fiber content, together with a sharp decrease of the elongation at break. The fibers′ incorporation into the biopolymer matrix brings about an enhancement in the mechanical strength and the impact strength of the composite. Dynamic mechanical thermal analysis (DMTA) investigation showed two relaxations occurring at about ?30 and 35°C. The addition of Alfa fibers enhanced the storage modulus E′ before and after T_α, which is consistent with the reinforcing effect of Alfa cellulose fibers. Copyright © 2008 John Wiley & Sons, Ltd.     

pH-Sensitive hydrogels based on polyhexamethyleneguanidine hydrochloride

The possibility to prepare pH-sensitive hydrogels based on polyhexamethyleneguanidine hydrochloride was explored. The equilibrium swelling rate of the hydrogels obtained at different monomer ratios was examined in relation to pH of the medium.     

Reaction based fluorescent probes for hydrogen sulfide

A reaction based fluorescence turn-on strategy for hydrogen sulfide (H(2)S) was developed. This strategy was based on a H(2)S-specific Michael addition-cyclization sequence. Other biological thiols such as cysteine and glutathione did not pursue the reaction and therefore did not turn on the fluorescence/consume the substrates. The probes showed good selectivity and sensitivity for hydrogen sulfide.