Biodegradable polyethylene glycol-based ionic liquids for effective inhibition of shale hydration

A series of ionic liquids based on polyethylene glycol (PEG) with different molecular weights were prepared for inhibiting shale hydration and swelling. The antiswelling ratio was measured to investigate the effect of different PEG-based ionic liquids on bentonite volume expansion, and it has shown that the ionic liquid based PEG200, i.e. PEG with molecular weight of 200, exhibited superior inhibition. The structures of the PEG200-based ionic liquids were characterized by ¹H NMR studies. The XRD results indicated that the PEG200-based ionic liquids intercalated into sodium montmorillonite (Na-MMT) reducing the water uptake by the clay. The formation of complexes of Na-MMT and PEG200-based ionic liquids was also verified by FTIR spectroscopy. Thermal degradation analysis suggested that the PEG200-based ionic liquids accessed the interlamellar spaces of Na-MMT and reduced the water content of the complexes obtained. Moreover, no breaks and collapse were observed on the shale samples after immersion in PEG200-based ionic liquid solutions. All the PEG200-based ionic liquids showed biodegradability and potential application in effective inhibition for clay hydration.

Phase morphology, thermomechanical, and crystallization behavior of uncompatibilized and PP-g-MAH compatibilized polypropylene/polystyrene blends

In this article, we discuss the phase morphology, thermal, mechanical, and crystallization properties of uncompatibilized and compatibilized polypropylene/polystyrene (PP/PS) blends. It is observed that the Young's modulus increases, but other mechanical properties such as tensile strength, flexural strength, elongation at break, and impact strength decrease by blending PS to PP. The tensile strength and Young's modulus of PP/PS blends were compared with various theoretical models. The thermal stability, melting, and crystallization temperatures and percentage crystallinity of semicrystalline PP in the blends were marginally decreased by the addition of amorphous PS. The presence of maleic anhydride-grafted polypropylene (compatibilizer) increases the phase stability of 90/10 and 80/20 blends by preventing the coalescence. Hence, finer and more uniform droplets of PS dispersed phases are observed. The compatibilizer induced some improvement in impact strength for the blends with PP matrix phase, however fluctuations in modulus, strength and ductility were observed with respect to the uncompatibilized blend. The thermal stability was not much affected by the addition of the compatibilizer for the PP rich blends but shows some decrease in the thermal stability of the blends, where PS forms the matrix. On the other hand, the % crystallinity was increased by the addition of compatibilizer, irrespective of the blend concentration.

Blue electrogenerated chemiluminescence from water-soluble iridium complexes containing sulfonated phenylpyridine or tetraethylene glycol derivatized triazolylpyridine ligands

Incorporating phenylpyridine- and triazolylpyridine-based ligands decorated with methylsulfonate or tetraethylene glycol (TEG) groups, a series of iridium(III) complexes has been created for green and blue electrogenerated chemiluminescence under analytically useful aqueous conditions, with tri-n-propylamine as a coreactant. The relative electrochemiluminescence (ECL) intensities of the complexes were dependent on the sensitivity of the photodetector over the wavelength range and the pulse time of the applied electrochemical potential. In terms of the integrated area of corrected ECL spectra, with a pulse time of 0.5 s, the intensities of the Ir(III) complexes were between 18 and 102 % that of [Ru(bpy)3 ](2+) (bpy=2,2'-bipyridine). However, when the intensities were measured with a typical bialkali photomultiplier tube, the signal of the most effective blue emitter, [Ir(df-ppy)2 (pt-TEG)](+) (df-ppy=2-(2,4-difluorophenyl)pyridine anion, pt-TEG=1-(2-(2-(2-(2-hydroxyethoxy)ethoxy)ethoxy)ethyl)-4-(2-pyridyl)-1,2,3-triazole), was over 1200 % that of the orange-red emitter [Ru(bpy)3 ](2+) . A combined experimental and theoretical investigation of the electrochemical and spectroscopic properties of the Ir(III) complexes indicated that the greater intensity from [Ir(df-ppy)2 (pt-TEG)](+) relative to those of the other Ir(III) complexes resulted from a combination of many factors, rather than being significantly favored in one area.

Analytically useful blue chemiluminescence from a water-soluble iridium(iii) complex containing a tetraethylene glycol functionalised triazolylpyridine ligand

We examine [Ir(df-ppy)2(pt-TEG)](+) as the first highly water soluble, blue-luminescent iridium(iii) complex for chemiluminescence detection. Marked differences in selectivity were observed between the new complex and the conventional [Ru(bpy)3](2+) reagent, which will enable this mode of detection to be extended to new areas of application.

The effect of polypropylene-graft-maleic anhydride on the morphology and dynamic mechanical properties of polypropylene/polystyrene blends

Polypropylene (PP) and polystyrene (PS) blends were prepared by melt processing in a haake at 180 °C. PP/PS blends are immiscible and the blend morphologies were characterized by scanning electron microscopy. The viscoelastic properties were characterized using dynamic mechanical analysis (DMA) with reference to blend ratio. The blend morphologies such as matrix droplet and phase inverted morphologies were observed. The storage modulus of the blends increased with increase in PS content and the value was maximum for neat PS. DMA showed changes in the polystyrene glass transition temperatures (Tg) over the entire composition range. There was a sharp increase in the Tg of PS with increasing PP content in the blend and a 12 °C elevation in Tg was observed. The increase in Tg was explained by proposing a new model based on the physical interaction between the blend components. It is assumed that the different effects by the PP phase resulted in the formation of constrained PS chains leading to high Tg values. The addition of PP-g-MAH has a positive effect on the morphology, increases the storage modulus, and decreases the Tg till 80/20 blends. However, for PP/PS blends with higher concentrations of PS, the PP-g-MAH has little effect or adverse effect on the morphology, and storage modulus, but decreases the Tg.

Free and restrained shrinkage behaviours of OPC and slag concretes with admixed polypropylene fibres

This paper presents the results of an investigation that studied the effects of admixed polypropylene (PP) fibres on the long-term drying shrinkage of hardened concrete. Five concrete mixtures, made with 100% Ordinary Portland Cement (OPC) as the binder and containing different volume fractions of PP fibre (0%, 0.05%, 0.1%, 0.2% and 0.5%) were tested. Also, three concrete mixtures were made with 65 % slag-blended cement binder incorporating 0% and 0.2% volume fraction of PP. The results show higher water loss and higher drying shrinkages in concretes that incorporate PP fibres than concrete without fibre. The results of early age cracking tendency of slag concrete, with and without fibre, under fully restrained and drying conditions, show that that PP fibre concrete had higher cracking tendency than concrete without fibre. Higher cracking tendency of PP fibre concrete was due to higher drying shrinkage and elastic moduli.

Nano-capsules of amphiphilic poly (ethylene glycol)-block-poly (bisphenol A carbonate) copolymers via thermodynamic entrapment

The synthesis of amphiphilic poly(ethylene glycol)-block-poly(bisphenol A carbonate) (PEG-b-PC) block copolymer is presented here using a simple bio-chemistry coupling reaction between poly(bisphenol A carbonate) (PC) with a monomethylether poly(ethylene glycol) (mPEG-OH) block, mediated by dicyclohexylcarbodiimide/4-dimethylaminopyridine. This method inherently allows great flexibility in the choice of starting materials as well as easy product purification only requiring phase separation and water washing. Collective data from Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR) and modulated dynamic scanning calorimetry (MDSC) confirmed the successful attachment of the poly(ethylene glycol) (mPEG-OH) and poly(bisphenol A carbonate) (PC) blocks. The preparation of nano-capsules was carried out by sudden addition of water to PEG-b-PC copolymers dispersed in THF, resulting in the controlled precipitation (i.e. thermodynamic entrapment) of the copolymer. Nano-capsules as small as 85 nm ± 30 nm were produced using this simple and fast methodology. We also demonstrate that encapsulating a water-insoluble bisphenol A diglycidyl ether (DGEBA) epoxy resin is possible highlighting the potential use of these capsules as a chemical delivery system.

Tailoring of interface of polypropylene/polystyrene/carbon nanofibre composites by polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene

Mechanical and physical properties of polypropylene (PP)/polystyrene (PS) blend, PP/PS/polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SEBS) ternary blend and their composites with carbon nanofibers (CNF) were investigated. Composites of ternary blend exhibited superior properties compared to those of binary blends. Mechanical performance of nanocomposites was intimately related to their phase morphology. PP/PS/SEBS/0.1 wt% CNF hybrid composites exhibited excellent impact strength (Four-fold increase compared to PP/PS blend) and ductility (12-fold increase in elongation at break, with respect to PP/PS blend). Moreover, these composites displayed good tensile strength and modulus (15% increase in Young's modulus, compared to PP/PS/SEBS blend) and are suitable for various end-use applications including automobile applications. Although crystallinity of PP phase is decreased by the incorporation of CNF, thermal stability of the composites remained almost unaffected. Contact angle measurements revealed that ternary composites exhibited maximum hydrophobicity.

Synthesis and self-assembly behaviour of poly(Nα-Boc-l-tryptophan)-block-poly(ethylene glycol)-block-poly(Nα-Boc-l-tryptophan)

We report for the first time the use of Nα-Boc-l-tryptophan for the synthesis of amphiphilic BAB triblock copolymers for potential drug delivery applications. A library of poly(Nα-Boc-l-tryptophan)-block-poly(ethylene glycol)-block-poly(Nα-Boc-l-tryptophan) (PBoclTrp-b-PEG-b-PBoclTrp) amphiphilic copolymers were synthesized through the ring opening polymerization of Nα-Boc-l-tryptophan Nα-carboxy anhydride as initiated by diamino-terminated PEG of fixed molecular weight (Mn 3350). The influence of the hydrophobic block length over self-assembly was investigated for 4 of the BAB copolymers of molecular weights varying between Mn 5000 and Mn 17000. It was found that an increase in hydrophobic block length led to an increase in hydrodynamic size of aggregates in solution, as well as a decrease in critical micelle concentration. TEM analysis showed the formation of spherical micelles with the largest of the copolymers forming interconnected networks of spherical micelles. The influence of hydrophobic block length over the formation of secondary structure was analyzed using circular dichroism and infrared spectroscopy. Collectively we found that the presence of t-Boc protected l-tryptophan leads to the preferential formation of α-helix secondary structure through hydrogen bonding, which, in a drug delivery vehicle context, could help in controlling drug release. Also, it is believed that the use of novel Nα-Boc-l-tryptophan could improve drug stabilization in the hydrophobic core via π-π interactions between indole rings.

Molecular interactions behind the synergistic effect in mixed monolayers of 1-octadecanol and ethylene glycol monooctadecyl ether

Mixed monolayers of 1-octadecanol (C18OH) and ethylene glycol monooctadecyl ether (C18E1) were studied to assess their evaporation suppressing performance. An unexpected increase in performance and stability was found around the 0.5:0.5 bicomponent mixture and has been ascribed to a synergistic effect of the monolayers. Molecular dynamics simulations have attributed this to an additional hydrogen bonding interaction between the monolayer and water, due to the exposed ether oxygen of C18E1 in the mixed system compared to the same ether oxygen in the pure C18E1 system. This interaction is maximized around the 0.5:0.5 ratio due to the particular interfacial geometry associated with this mixture.