Reconfigurable and Latchable Shape‐Morphing Dielectric Elastomers Based on Local Stiffness Modulation

Programmable soft materials exhibiting dynamically reconfigurable, reversible, fast, and latchable shape transformation are key for applications ranging from wearable tactile actuators to deployable soft robots. Multimorph soft actuator sheets with high load‐bearing capacity are reported, capable of bending on multiple axis, made by combining a single dielectric elastomer actuator (DEA) with two layers of shape memory polymers (SMPs) fibers and an array of stretchable heaters. The rigidity of the SMP fibers can be reduced by two orders of magnitude by Joule heating, thus allowing the orientation and location of soft and hard regions to be dynamically defined by addressing the heaters. When the DEA is then actuated, it bends preferentially along the soft axis, enabling the device to morph into multiple distinct configurations. Cooling down the SMPs locks these shape changes into place. A tip deflection angle of over 300° at 5 kV is achieved with a blocking force of over 27 mN. Devices using two antagonistic DEAs are also reported that attain more complex shapes. Multimorphing is demonstrated by gripping objects with different shapes. An analytical model is developed to determine the design parameters that offers the best trade‐off between large actuation and high holding forces.     

Bi(III)4-methylpiperidinedithiocarbamate coprecipitation procedure for separation--pre-concentration of trace metal ions in water samples by flame atomic absorption spectrometric determination

A pre-concentration method was developed for determination of trace amounts of cadmium, copper and lead in water samples by FAAS after coprecipitation by using potassium 4-methylpiperidinedithiocarbamate (K4-MPDC) as a chelating agent and Bi(III) as a carrier element. This procedure is based on filtration of the solution containing precipitate on a cellulose nitrate membrane filter following Cd(II), Cu(II) and Pb(II) coprecipitation with Bi(III)4-MPDC and then the precipitates together with membrane filter were dissolved in concentrated nitric acid. The metal contents of the final solution were determined by FAAS. Several parameters including pH of sample solution, amount of carrier element and reagent, standing time, sample volume for precipitation and the effects of diverse ions were examined. The accuracy of the method was tested with standard reference material (MBH, C31XB20 and CRM BCR-32) and Cd, Cu and Pb added samples. Determination of Cd, Cu and Pb was carried out in sea water, river water and tap water samples. The recoveries were >95%. The relative standard deviations of determination were less than 10%.     

Synthesis and electrochemical,electrochromic and electrical properties of novel s-triazine bridged trinuclear Zn(II), Cu(II) and Lu(III) and a tris double-decker Lu(III) phthalocyanines

The new s-triazine-bridged trinuclear Zn(II) and Cu(II) phthalocyanines have been synthesized from the reaction of corresponding anhydrous metal salts, Zn(OAc)₂ and CuCl with 4,5-bis(hexylthio)-phthalonitrile and 2,4,6-tris(2-thiophthalonitrile)-s-triazine. The tris phthalonitrile derivative of s-triazine was prepared from the reaction of 4-nitrophthalonitrile and thiocyanuric acid in dry dimethylformamide as solvent using K₂CO₃ as the base. The same route was applied to prepare the trinuclear Lu(III) phthalocyanine analogue. The conversion of tris phthalonitrile into its isoindoline derivative was accomplished by bubbling ammonia gas through a solution in methanol in the presence of sodium methoxide. The cyclization of two different isoindoline derivatives and 4,5-bis(hexylhthio)-1,2-diiminoisoindoline, with lutetium (III) acetate in dimethylformamide gave trinuclear Lu(III) phthalocyanine. The reaction of this complex with octakis-hexylthio phthalocyanine led to the isolation of tris double-decker Lu(III) phthalocyanine. The structures of the target compounds were confirmed by elemental analysis, UV–vis, IR and MALDI-TOF mass spectroscopies. The d.c. and a.c. conductivities of the phthalocyanine compounds were measured as a function of temperature. The small value of pre-exponential factor suggested the conduction by localized states in the band tails and by localized states near the Fermi level. The temperature dependence of the frequency exponent showed that the conduction in these compounds is due to hopping of charge carriers. The tris double-decker phthalocyanine complex showed well-defined electrochromic behaviour with green-blue and blue-purple colour transitions.     

Electrorheological properties of kaolinite,polyindole, and polyindole/kaolinite composite suspensions

In this study, polyindole (PIN) and polyindole/kaolinite (PIN/KAO) composite were synthesized by free radical polymerization using FeCl₃ as an initiator. Average particle sizes (d₅₀) of PIN and PIN/KAO composite were determined by dynamic light scattering (DLS) as 7.2 and 6.2 μm, respectively. The samples were characterized by FTIR, elemental analysis, DSC/TGA and SEM measurements. Suspensions of KAO, PIN, and PIN/KAO composite were prepared in silicone oil (SO) and the sedimentation stabilities were determined. Electrorheological (ER) properties of these suspensions were studied as a function of dispersed phase concentration, shear rate, shear stress, and temperature; and yield stresses and excess shear stresses determined. Further, dielectric properties of KAO, PIN, and PIN/KAO composite were investigated. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Synthesis, characterization, and cyclopolymerization of a functional non-symmetric divinyl monomer

A non-symmetric divinyl monomer with terminal carboxylic acid functionality was readily synthesized from the reaction of ethyl α-hydroxymethylacrylate (EHMA) with maleic anhydride. The new monomer (EHMA-MA) was homopolymerized in both bulk and ethyl acetate using AIBN as an initiator to give cyclopolymers. The synthesis of the monomer and cyclopolymers were followed by ¹³C NMR, ¹H NMR, and FTIR. ¹H NMR was also utilized to obtain the degree of cyclization of the polymers, which were found to be 95% or higher in all cases. The molecular weights of the cyclopolymers were around 40-60,000 g/mol as estimated by SEC. The cyclopolymers were thermally stable up to 150 °C. Although the cyclopolymers obtained were not water-soluble; they were soluble in aqueous 1 M NaOH solution. In addition to the carboxylic acid functionality present, the cyclopolymers also had an ethyl ester and a lactone moiety. These functional groups were reacted with hexylamine to obtain a polymer with imide and amide moieties.     

Amine-functionalized sol-gel-based lab-in-a-pipet-tip approach for the fast enrichment and specific purification of phosphopeptides in MALDI-MS applications

Amine-functionalized sol-gels were investigated for the enrichment and purification of phosphopeptides from digested protein mixture solutions. Tetramethylorthosilicate (TMOS) and N'[3-(trimethoxysilyl)-propyl]-diethylenetriamine (TPDA) were used in a 1:1 mole ratio in the production of amine-functionalized sol-gels. The sol-gel network was then used for phosphopeptide enrichment. Phosphopeptide enrichment onto the synthesized amine-functionalized sol-gels was performed using an enolase digested peptide mixture, a β-casein digested peptide mixture, as well as these digested peptide mixtures contaminated 50-fold with bovine serum albumin (BSA). Moreover, phosphopeptide enrichment was successfully performed using nonfat milk as a highly contaminated and complex material. In each phosphopeptide enrichment and purification process, only phosphopeptides were enriched and separated from the other digested peptides. Phosphopeptides were adsorbed onto the amine-functionalized sol-gels at pH 4.0 and eluted at pH 1.0 using trifluoroacetic acid (TFA). For phosphopeptide analysis by MALDI-MS, a 2,5-dihydroxybenzoic acid matrix containing 1.0% phosphoric acid was used to overcome the degradation of phosphopeptides and provide high intensity phosphopeptide protonated molecular ion signal intensities. It was also found that phosphopeptide detection limits were improved to approximately 10 femtomoles. For rapid and specific phosphopeptide enrichment and purification, sol-gel materials were placed in a 10 μL pipet tip with glass wool on either side. Phosphopeptide enrichment from digested peptide mixtures was performed in a very short time (less than 1 min) at subpicomole levels using this novel lab-in-a-pipet-tip approach.     

Hydrogen production by aqueous phase catalytic reforming of glycerine

Hydrogen is believed to be the one of the main energy carriers in the near future. In this research glycerine, which is produced in large quantities as a by-product of biodiesel process, was converted to hydrogen aiming to contribute to clean energy initiative. Conversion of glycerol to hydrogen was achieved via aqueous-phase reforming (APR) with Pt/Al₂O₃ catalyst. The experiments were carried out in an autoclave reactor and a continuous fixed-bed reactor. The effects of reaction temperature (160-280 °C), feed flow rate (0.05-0.5 mL/dak) and feed concentration (5-85 wt-% glycerine) on product distribution were investigated. Optimum temperature for hydrogen production with APR was determined as 230 °C. Maximum gas production rate was found at the feed flow rates around 0.1 mL/min. It was also found that hydrogen concentration in the gas product increased with decreasing glycerol concentration in the feed.