Ionic liquids and plastic crystals based on tertiary sulfonium and bis(fluorosulfonyl)imide

A new series of low-melting, low-viscosity, hydrophobic ionic liquids based on relatively small tertiary sulfonium cations ([R¹R²R³S]⁺, wherein R¹, R², R³ = CH₃ or C₂H₅, R³ = CH₂CH₂OCH₃, CH₂CH₂COOCH₃, CH₂CH₂CN) and bis(fluorosulfonyl)imide (FSI⁻) anion have been prepared and characterized. The important physicochemical and electrochemical properties of these salts, such as melting point, glass transition, viscosity, density, ionic conductivity, thermal and electrochemical stability, have been determined. The influence of structure variation in the tertiary sulfonium cations on the above physicochemical properties is discussed. Among these new salts, some of them show the desirable properties including low-melting points, low viscosities, and high conductivities, to be selected as potential candidates as electrolytes in energy devices, and two salts are ionic plastic crystals.     

Effect of multiple extrusions on the impact properties of polypropylene/clay nanocomposites

Polypropylene (PP)‐based polymer nanocomposites containing organically modified montmorillonite (OMMT) with and without maleic anhydride grafted PP, were compounded by twin‐screw extrusion. The extrusion process was repeated various numbers of times to increase the extruder residence time (T_R) and, through that, the particle dispersion. Rheological measurements fitted to a modified Carreau–Yasuda model defining a melt yield stress were used to indicate changes in the particle dispersion with regard to T_R. This analysis showed a monotonically increased dispersion of clay particles in the PP matrix with increasing extruder T_R. The small‐strain tensile properties were tested at both ambient (20°C) and elevated (90°C) temperatures, and no significant changes were observed in the tensile strength or modulus as a function of T_R. Instrumented Izod impact tests showed that the nanocomposite impact strength (σ_i) increased monotonically with increased T_R by 70% from least dispersed to best dispersed, which was still 20% below the level for neat PP. Both the fracture initiation energy and propagation energy increased with T_R, but the primary effect on σ_i came from the fracture propagation energy, which delivered 80% of the improvement. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis and characterization of macrocyclic nickel(II) complexes with α-methylbenzyl groups as chiral pendants

Novel nickel(II) hexaaza macrocyclic complexes, [Ni(L^R,R)](ClO₄)₂ (1) and [Ni(L^S,S)](ClO₄)₂ (2), containing chiral pendant groups have been synthesized by an efficient one-pot template condensation and characterized (L^R,R/S,S = 1,8-di((R/S)-α-methylbenzyl)-1,3,6,8,10,13-hexaazacyclotetradecane). The crystal structures of 1 and 2 were determined by single-crystal X-ray analysis. Each complex has a square-planar coordination environment for the nickel(II) ion, and is either an R or an S enantiomorph depending on the pendant groups. The circular dichroism spectrum of 1 showed a negative, positive and negative peak at 345, 440, and 492 nm, respectively, and that of 2 exhibited an enantiomeric pattern.     

Nonisothermal crystallization kinetics of linear metallocene polyethylenes

The effect of weight‐average molecular weight (M_w) on the nonisothermal crystallization kinetics of linear metallocene polyethylene (m‐PE) was studied with modulated differential scanning calorimetry. Six linear m‐PEs of molecular weights in the range 122–934 kg/mol were prepared by gas‐phase polymerization. The cooling rate (R) was varied in the range 2–20°C/min, and it significantly affected the crystallization behavior. M_w had a weak influence on both the peak crystallization temperature and the crystallization onset temperature. All m‐PEs showed primary and secondary crystallizations. At both low and high R's, the crystallinity showed a significant drop (～ 30%) when M_w was increased from 122 to 934 kg/mol. At low R's (< 10°C/min), the rate parameters in the modified Avrami method [primary rate constant (k_R)] and Mo method [F(T)] of analyses agreed in suggesting that an increased M_w slowed the rate of crystallization. The M_w dependency of k_R followed the Arrhenius type (k_R = k_Roe²⁸¹/M_w, where k_Ro is a rate‐dependent constant). However, at higher R's, k_R approached a constant value. The order parameters obtained by the different methods of analysis (n and α) were independent of M_w, which suggests that the crystal type remained the same. Hoffman–Lauritzen theory was used for data analysis, and activation energy per segment showed a significant decrease, from 225.0 to 11.8 kJ/mol, when M_w was increased from 152 to 934 kg/mol. Finally, all methods of analysis suggested a significant effect of M_w on slowing the overall crystallization process. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Electrochemical behaviour of poly(pyrrole) coatings on steel

The electrochemical and corrosion protective properties of electrochemically deposited thin films of polypyrrole (PPy) have been studied. Two systems have been investigated: (1) Oxalate-doped PPy; and (2) a dual layer system consisting of PPy-oxalate and PPy-poly(styrene sulfonate). Large anions like PSS are interesting, because they possibly prevent ingress into the layer by halide ions like chloride. Open circuit potential measurements and impedance spectra of both systems are compared. For intact coating systems the impedance spectra of the four systems investigated can be described by an equivalent circuit model consisting of an R _f Q _f circuit, due to the polypyrrole film itself, and a modified Randles circuit in series, to account for the double layer at the polypyrrole/electrolyte interface and the polypyrrole reaction. In 0.1 m NaCl the time to failure for the dual layer is almost 6-fold that of the single layer. This indicates that PSS is indeed capable of preventing the ingress of chloride ions. In 0.1 m Na₂SO₄ the time to failure for the dual layer is less than double that of the single layer.     

A crosslinked waterborne poly(urethane-urea) oligomer enables mechanically strong waterborne polyacrylate–poly(urethane-urea) hybrid films with superior film-forming ability

In this article, a crosslinked waterborne poly(urethane-urea) (WPUU) is synthesized based on the terminal aromatic amine polyether (DP-1000) and aliphatic isophorone diisocyanate. Then WPUU is compound with acrylate monomer by emulsion polymerization to produce waterborne polyacrylate–poly(urethane-urea) (WPUUA) hybrid emulsions. Compared with waterborne polyacrylate (WPA) film, the film-forming ability of WPUUA film is improved and the surface roughness R_a and R_q of WPUUA film decreases from 47.5 and 36.4 nm to 35.2 and 18.8 nm, respectively. Meanwhile, the mechanical properties of WPUUA films are significantly improved compared to WPA film. In addition, the performances of WPUUA hybrid films can be modified according to requirements by adjusting the molar ratio between DP-1000 and polyisocyanate. As a result, these WPUUA hybrid emulsions have great application potential in waterborne coatings and other fields.     

All-inorganic flexible high-temperature strain sensor based on SrRuO3/muscovite heteroepitaxy

Design and fabrication of flexible strain sensors are still challenging for high-temperature application in the aerospace, metallurgical industry, and underground energy exploration. In the present work, an all-inorganic flexible strain sensor has been fabricated based on single-crystal SrRuO₃ (SRO) thin films epitaxially grown on muscovite. A high resistive tunability ((∆R/R₀%) ∼ 26.05%), excellent linearity (correlation coefficient of 0.93), and large gauge factor (GF ∼ 101) have been achieved in the as-prepared SRO-based sensors with great bending durability. The mechanism for the tunability of the electrical transport in flexible SRO thin films under mechanical bending is proposed based on the Raman and X-ray photoelectron spectroscopy results. The sensors have been confirmed to work properly from ambient temperatures up to ∼425 K, showing the potential application in high-temperature environments. Moreover, the flexible sensors have the ability to monitor the hand joint movements.     

Structure–Activity Relationship Studies on (R)‐PFI‐2 Analogues as Inhibitors of Histone Lysine Methyltransferase SETD7

SETD7 is a histone H3K4 lysine methyltransferase involved in human gene regulation. Aberrant expression of SETD7 has been associated with various diseases, including cancer. Therefore, SETD7 is considered a good target for the development of new epigenetic drugs. To date, few selective small‐molecule inhibitors have been reported that target SETD7, the most potent being (R)‐PFI‐2. Herein we report structure–activity relationship studies on (R)‐PFI‐2 and its analogues. A library of 29 structural analogues of (R)‐PFI‐2 was synthesized and evaluated for inhibition of recombinantly expressed human SETD7. The key interactions were found to be a salt bridge and a hydrogen bond formed between (R)‐PFI‐2′s NH₂⁺ group and SETD7′s Asp256 and His252 residue, respectively.     

Syntheses and Structural Characterization of Triorganotin Derivatives of Bis(carboxymethyl)trithiocarbonate: X-ray Crystal Structures of 2D Network Polymers

Six triorganotin(IV) complexes of the type {(R₃Sn)₂[C₃S₃(COO)₂]}_n (R = C₆H₅ 1; n-Bu 2; PhCH₂ 4; p-F-PhCH₂ 5; o-F-PhCH₂ 6) and {(R₃Sn)₂[C₃S₃(COO)₂]}_n·[EtOH] (R = Me 3) have been synthesized by the reaction of bis(carboxymethyl)trithiocarbonate with triorganotin(IV) chloride in the presence of sodium ethoxide. All complexes were characterized by elemental analysis IR, ¹H, ¹³C and ¹¹⁹Sn NMR spectroscopy. Except for 4–6, all complexes were also characterized by X-ray crystallography. The X-ray date revealed that complexes 1–3 show two-dimensional network polymeric structure in which the geometries of tin atoms are trigonal bipyramid with the axial positions occupied by carboxylic oxygen atoms.     

Primary and secondary distributions after a small-amplitude potential step at disk electrode coated with conducting film

The set of equations and boundary conditions for the “primary potential/current distribution” after a small-amplitude potential step has been analyzed for a film-coated disk electrode in contact with an electrolyte. The solution of these equations provides the overall short-time resistance of this system, R_tot, which is determined by the short-time resistance of the electrolyte solution in contact with the bare disk electrode, R_s, and the short-time film resistance to the current passage in the normal direction, (r_o, disk radius; L_f, film thickness; κ_f, its specific conductivity). The deviation of R_tot from the sum of these resistances, R_s + R_f, originates from a three-dimensional potential/current distribution in solution. Procedures to calculate the film resistance and its specific conductivity on the basis of the measured values of R_tot and R_s have been proposed. Similar analysis has also been carried out for the “secondary potential/current distribution” in the same system. The overall resistance for this regime is related to the short-time solution resistance, R_s, and to the total resistance of the electrode, equal to the sum of the resistance, R_f, and two interfacial resistances, R_m/f and R_f/s. A method to determine the bulk-film parameters, R_f and κ_f, from data for the secondary distribution is discussed. Advantages and restrictions of the proposed route to transport parameters of a film at the electrode surface are analyzed, in comparison with existing methods of their determination.     

Peroxydisulfate initiated graft copolymerization of aniline onto poly(propylene) fiber—A kinetic approach

A novel method for the preparation of electrically conducting fibers through chemical grafting of electrically conducting polymer onto poly(propylene) (PP) fiber is described. The graft copolymerization of aniline (ANI) was performed in aqueous acidic medium by using a chemical oxidant such as peroxydisulfate (PDS). Grafting occurred with simultaneous homopolymer formation. The content of polyaniline in the backbone fiber was found to vary by varying [monomer], [initiator], and amount of PP fiber. Various graft parameters such as rate of grafting (R_g), % grafting, and % grafting efficiency were evaluated. The rate of homopolymerization (R_h) was also determined. Both R_h and R_g showed first‐order dependency on [ANI], [PDS], and amount of PP fiber variation. The chemical grafting was confirmed by use of cyclic voltammetry and conductivity measurements. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3827–3834, 2003     

Dynamic deposition of polyacids on porous membrane supports

Poly(acrylic acids), poly(styrenesulfonic acid), and their block and random copolymers were tested for their ability to form dynamic membranes on partially cured asymmetric cellulose acetate. Chemically modified porous polypropylene (Celgard) was also used as a support for poly(acrylic acid). Salt rejections, water fluxes, and streaming potentials of membranes were tested under hyperfiltration conditions. Sorption of the polyelectrolytes by the cellulose acetate supports was studied using spectrophotometric, ²²Na tracer, and electron microscopy techniques. The dynamic membrane formation was noted only for poly(acrylic acid) and for its 1:4:1 block copolymer with poly(styrenesulfonic acid). The uneffectiveness of other polyelectrolytes was discussed in terms of a negative zeta potential of cellulose acetate. The increase in salt rejection (R) due to the polyelectrolyte is strongly dependent on the initial R_i of the support. Sharp maxima in the ΔR -versus-R_i curves have been noted for R_i in the range of 40–55%. The most significant improvement in the hyperfiltration characteristics of cellulose acetate was attained with the 1:4:1 block copolymer. Flux of 17 gfd at 350 psi and R = 93% was obtained in short-term tests for a 0.1N feed solution. Long-term tests did not reveal any flux or salt rejection decline for membranes in which poly(acrylic acid) was complexed with phosphoramidic groups grafted onto Celgard.     

Enantioselective Separation of Racemic Amlodipine by Two-Phase Chiral Extraction Containing O,O′-Dibenzoyl-(2S,3S)-Tartaric Acid as Chiral Selector

A two-phase chiral extraction system containing O,O′-dibenzoyl-(2S,3S)-tartaric acid ((+)-DBTA) in 1-decanol organic phase and aqueous phase was developed for the chiral resolution of amlopidine. The effects of extractant concentration, equilibrium time, and pH of the aqueous phase on the separation performance were investigated. The results indicated that the system afforded a strong chiral separation ability; the (+)-DBTA showed a higher recognition ability toward (S)-amlodipine than the (R)-amlodipine. Upon a single extraction, the enantiomeric excess (%) of (S)-amlodipine could be enriched to 24.27%. The product recovery ratio was 0.74. The distribution ratios for (S)-amlodipine (D _S ), (R)-amlodipine (D _R ) and separation factor (α) were 1.28, 0.78, and 1.64, respectively. Therefore, the pH and concentration of the extractant have the great effects on chiral separation ability. Two-phase chiral extraction has great significance for preparative separation of (S)-amlodipine; it can also be used to design and scale up the enantioselective separation process.     

Synthesis,spectral and structural study of sulfur-containing copper(II) complexes

A series of four new copper(II) complexes [Cu(H₂L)(L¹)] 1, [Cu(H₂L)(PMDT)] 2, [Cu(H₂L)(Dien)] 3 and [Cu(H₂L)(L²)] 4 have been synthesized by template condensation (H₂L=thiodiglycolic acid, L¹=N-[(1)-1-(4-methylphenyl)ethylidene]benzohydrazide, PMDT=N,N,N′,N′,N ^′′-pentamethyldiethylene- triamine, Dien=diethylenetriamine L²=N-[(1)-pyridin-2-ylmethylidene]benzohydrazide). The bonding and stereochemistry of the complexes have been characterized by molar conductance, elemental analysis, magnetic susceptibility, infrared, UV–visible, electron paramagnetic resonance structural studies and electrochemical studies. g-Values were calculated for all complexes in polycrystalline form as well as in DMSO solution. The magnetic and spectral data indicate square pyramidal geometry for 1 and octahedral geometry for 2–4 complexes. Cyclic voltammograms for all the complexes are similar and involve two irreversible redox processes. Their biological properties have also been studied. The thio complexes show more antibacterial activity than the controlled one. The antibacterial activities of the compounds have also been tested against Escherichia coli with different concentrations.     

Polymerization of acrylamide and methacrylamide initiated by a potassium peroxydiphosphate/Mn(II) system

The kinetics of aqueous polymerization of acrylamide (AM) and methacrylamide (MAM) have been studied using a potassium peroxydiphosphate (PDP/Mn(II) system in an inert atmosphere at 40°C and at constant pH (1·30). The polymerization rate R_p has been found to be proportional to the half power of PDP and Mn(II) concentrations. The overall energy of activation (ΔE) was found to be 40·2±0·1kJmol^-1 and 45·0±0.1kJmol^-1 for AM and MAM, respectively. Intrinsic viscosity [η], viscometric average molecular weight (M_v) and number average degree of polymerization (P_n) at different concentrations of PDP, Mn(II) and monomer are reported. © 1998 SCI.     

Kinetic and mechanistic studies on the block copolymerization of methyl methacrylate initiated by Ce4+-poly (ethylene glycol) redox system

The kinetic and mechanistic features of tetravalent cerium-poly(ethylene glycol) (PEG, molecular weight 6000) redox couple initiated block copolymerization of methyl methacrylate (MMA) have been investigated in aqueous acidic medium in the temperature range 30–50°C. The block copolymerization behavior as a function of [Ce⁴⁺], [PEG], [MMA], [H⁺], [NO₃⁻], as well as temperature, have been studied. The overall rate of polymerization (R_p), the rate of disappearance of Ce⁴⁺ (R_Ce), and the number average molecular weight (M _n) have been determined from gravimetry, cerimetry, and gel permeation chromatography, respectively. R_p has been found to bear a square dependence on [MMA] and independent of both [Ce⁴⁺] and [H⁺]. R_Ce has been found to be directly proportional to [Ce⁴⁺] and [H⁺], and independent of [MMA]. Both R_p and R_Ce have been found to be retarded on adding nitrate ions, while increase of temperature accelerated the rates. The M _n of the block copolymer has been found to depend on [Ce⁴⁺], [PEG], [MMA], and [H⁺] as well as on temperature. A plausible reaction scheme has been derived and suitable kinetic expressions have been evaluated based on these observations. It has been concluded that by varying the temperature and concentration of the components of the redox system, it is possible to control the rate of polymerization and the molecular weight of the resulting block copolymer. © 1997 John Wiley & Sons, Inc.     

Photopolymerization of Methyl Methacrylate Sensitized by Tris(2,2′-bipyridine)iron(III)

The photopolymerization of methyl methacrylate (MMA) sensitized by tris(2,2′-bipyridine)iron(III ) complex, [Fe(bpy)₃]³⁺, was studied at 35°C in the presence of an electron donor, triethylamine (TEA) with UV radiation of wavelength 254nm. The initial rate of polymerization, R_p, shows a linear dependence on [MMA] with an exponential value of 1·18±0·04. R_p varies linearly with the square root of the photosensitizer concentration up to 2·00×10^-4moll^-1, and above this concentration, R_p decreases with the increase of photosensitizer concentration. The rate of polymerization is not affected by the concentration of the co-initiator, [TEA]. A suitable mechanism for the reaction is proposed to explain the kinetics of the reaction. © 1997 SCI.     

Lower critical solution temperatures of thermo‐responsive poly(N‐isopropylacrylamide) copolymers with racemate or single enantiomer groups

BACKGROUND: Thermo‐responsive copolymers with racemate or single enantiomer groups are attracting increasing attention due to their fascinating functional properties and potential applications. However, there is a lack of systematic information about the lower critical solution temperature (LCST) of poly(N‐isopropylacrylamide)‐based thermo‐responsive chiral recognition systems. In this study, a series of thermo‐responsive chiral recognition copolymers, poly[(N‐isopropylacrylamide)‐co‐(N‐(S)‐sec‐butylacrylamide)] (PN‐S‐B) and poly[(N‐isopropylacrylamide)‐co‐(N‐(R,S)‐sec‐butylacrylamide)] (PN‐R,S‐B), with different molar compositions, were prepared. The effects of heating and cooling processes, optical activity and amount of chiral recognition groups in the copolymers on the LCSTs of the prepared copolymers were systematically studied. RESULTS: LCST hysteresis phenomena are found in the phase transition processes of PN‐S‐B and PN‐R,S‐B copolymers in a heating and cooling cycle. The LCSTs of PN‐S‐B and PN‐R,S‐B during the heating process are higher than those during the cooling process. With similar molar ratios of N‐isopropylacrylamide groups in the copolymers, the LCST of the copolymer containing a single enantiomer (PN‐S‐B) is lower than that of the copolymer containing racemate (PN‐R,S‐B) due to the steric structural difference. The LCSTs of PN‐R,S‐B copolymers are in inverse proportion to the molar contents of the hydrophobic R,S‐B moieties in these copolymers. CONCLUSION: The results provide valuable guidance for designing and fabricating thermo‐responsive chiral recognition systems with desired LCSTs. Copyright © 2008 Society of Chemical Industry     

Structure of an antioxidant from fermented soybeans (tempeh)

In an exhaustive investigation of the antioxidative properties of tempeh constituents, the substance at R _f 0.58 (cyclohexane/ethyl ether, 9:1) was isolated and purified. Until now, only the ultraviolet and fluorescence data of the substance were known, and the presence of an OH group was indicated. In the present paper, the structure of the substance at R _f 0.58 was elucidated by the application of spectroscopic methods and found to be 5-(δ-tocopheroxy)-δ-tocopherol. That previous researchers did not confirm antioxidant activity in tempeh oil has been related to the way the tempeh oil was prepared. Previous suggestions regarding the substance at R _f 0.58 as being one of the main tempeh antioxidants could not be proved. The antioxidative effect of tempeh oil seems to be the result of a synergistic effect of tocopherols (present in the soybeans) and amino acids (liberated during the fermentation process with Rhizopus oligosporus).     

Molecular design of damping rubber based on polyacrylate‐containing silicone

A series of damping rubbers based on poly(meth)acrylate and poly(meth)acrylate‐containing silicone rubbers has been prepared. The dynamical mechanical properties were evaluated by using a dynamic mechanical viscoelastometer (DMA). A detailed investigation is reported on the relationship of the damping capability of the poly(meth)acrylate rubbers with their composition and macromolecular architecture. Also discussed is the effect of two kinds of silicone elastomers on the damping performance of the polyacrylate‐containing silicone rubber. The results indicate that, in vulcanized rubber systems, both statistical copolymerization for multiple monomers and blending between immiscible polymers with close T_gs facilitate broadening the glass transition peaks. Furthermore, the molecular design is quite an effective approach in which the multiple monomers whose polymers have a ladder‐changing T_g are used to synthesize the damping rubber with the broad effective functional area. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 746–751, 2002