Structural investigation of hydrate compounds of the tetraisoamylammonium form of polyacrylate ion exchange resins. Crystal structure of a clathrate hydrate of linear tetraisoamylammonium polyacrylate

A polyhydrate of the tetraisoamylammonium salt of linear (uncrosslinked) polyacrylate (～25 monomeric units in the polyacrylate chain) is described and compared to polyhydrates of cross-linked tetraisoamylammonium polyacrylates (0.5–3% of cross-linking with divinylbenzene or divinylsulfide). Powder X-ray diffraction reveals that the polyhydrate containing a linear polyacrylate molecule has the same structure (hexagonal, a = 12.26 Å, c = 12.71 Å at 3°C) as polyhydrates of the cross-linked polyacrylate molecules. A single crystal of the polyhydrate obtained from an aqueous solution of linear tetraisoamylammonium polyacrylate is studied by X-ray diffraction at ?173°C. The structure is hexagonal; space group P-6m2; the polyhydrate framework is a slightly distorted variant of the hexagonal structure-I of clathrate hydrates.     

Double clathrate hydrates of tetrabutylammonium fluoride + helium, neon, hydrogen and argon at high pressures

Decomposition curves of double ionic clathrate hydrates of tetrabutylammonium fluoride with helium, neon, hydrogen and argon were studied at pressures up to 800 MPa. Formation of double hydrates with helium, neon and hydrogen does not lead to any significant increase of the temperatures of decomposition of these hydrates; at high temperatures the hydrates may decompose even at lower temperatures than the hydrate of pure tetraalkylammonium salt does. Decomposition temperatures of double hydrates with argon in all cases were 4–8 °C higher in comparison with the decomposition temperature of ionic clathrate hydrates of tetrabutylammonium fluoride. We suppose that this behavior is caused by simultaneous effect of three factors on hydrate decomposition temperature: (1) partial filling of the small cavities in the framework of the hydrate with water molecules, (2) weakness of the van der Waals interactions between the gas molecules and the host water molecules, and (3) dissolution of helium, hydrogen and neon in the solution of tetrabutylammonium salt causing a decrease of melting temperatures of the hydrates formed from these solutions.     

Thermal analysis of manganese(II) complexes of general formula (Bu4N)2[MnBrnCl4−n]

Thermal decomposition of compounds consisting of tetrahalogenomanganese(II) anions, [MnBr_nCl_4?n]^2? (n = 0–4), and a tetrabutylammonium cation has been studied using the DSC, TG-FTIR, TG–MS and DTA techniques. The measurements were carried out in an argon and static air atmospheres over the temperature ranges 173–450 K (DSC) and 300–1073 K (TG). Solid products of the thermal decomposition were identified by FT-FIR spectroscopy as well as X-ray powder diffractometry.     

Hydrolytic degradation of poly(d,l-lactide-co-glycolide 50/50)-di-acrylate network as studied by liquid chromatography-mass spectrometry

The soluble products of the hydrolytic degradation of photochemically cross-linked poly-(d,l-lactide-co-glycolide 50/50)-di-acrylate film were analysed at different stages to obtain insight into the complex (bio)degradation processes. Liquid chromatography-mass spectrometry analyses have been used to identify and quantify the various oligomeric and polymeric degradation products from the soluble fraction. The products were analysed directly after release and also after complete hydrolysis of the soluble fraction. The study shows a rapid release of residual photo-initiator followed by a gradual release of lactide/di-ethyleneglycol/glycolide oligomers with varying composition and chain length. The final stage of the sigmoidal weight loss profile reflects the release of polyacrylate chains with lactide/glycolide side chains. The molecular weights of the polyacrylate chains released increase with degradation time, which indicates that the release of these polyacrylate chains is determined by the number and type of ester-groups that must be degraded hydrolytically to dissolve these chains. The analysis of the soluble degradation products provides detailed insights in the chemical changes at the different stages of degradation; extraction, network attack, network penetration, bulk degradation, and finally release of persistent network fragments. Chromatographic and mass spectrometric techniques prove to be powerful tools to enhance the understanding of the hydrolytic degradation of chemically cross-linked acrylates.     

Molecular dynamics simulation of water diffusion inside an amorphous polyacrylate latex film

Molecular dynamics simulations were applied to investigate the diffusion behaviors of water molecules at temperatures ranging from 323 to 443 K inside amorphous polyacrylate. The results showed that the simulated diffusion coefficients and activation energies were similar to those of experiments. Moreover, the activation energy of water molecules at high temperatures was higher than that at low temperatures by 3.16 kcal mol^?1, which was close to the hydrogen‐bonding energy between water and polyacrylate. An analysis of the experimental desorption curves of water molecules and their activation energies has confirmed that there are two forms of water molecules inside rubbery polyacrylate, namely, free water and bound water. In addition, it has been concluded that bound water molecules move from one polar group of polyacrylate to another, and this is followed by occasional jumps. Simulated information is very helpful in designing new polyacrylate latex systems and optimizing existent polyacrylate systems. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 884–891, 2007     

Preparation of novel cross-linked fluoroalkyl end-capped cooligomeric nanoparticles–encapsulated cytochrome c in water and ionic liquids

Cross-linked fluoroalkyl end-capped acrylic acid cooligomer containing poly(oxyethylene) units can form the nanometer size-controlled fine particles in aqueous solutions, and these cross-linked nanoparticles interact with cytochrome c (Cyto-c) to afford the corresponding cooligomeric nanoparticles–encapsulated Cyto-c effectively. Interestingly, we can easily isolate the fluorinated nanoparticles–encapsulated Cyto-c powder by the simple centrifugal separation of the corresponding aqueous solutions. The cross-linked fluorinated cooligomer also enables an effective transfer of Cyto-c from aqueous solution to ionic liquids such as 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide to afford the immobilized Cyto-c with the corresponding fluorinated cooligomer in quantitatively immobilized ratio (～100%). The immobilized Cyto-c exhibited a good dispersibility in the parent ionic liquid to afford the nanometer size-controlled fluorinated particles–encapsulated Cyto-c. Similarly, the cross-linked fluorinated cooligomer in ionic liquids such as 3-methylpyrazolium tetrafluoroborate (3MP-BF4) interacted with Cyto-c to afford the corresponding nanoparticles–encapsulated Cyto-c in quantitatively encapsulated ratio (～100%). These cross-linked fluorinated nanoparticles–encapsulated Cyto-c in water and ionic liquids were applied to the oxidation of guaiacol with hydrogen peroxide, and an extremely higher catalytic activity for this oxidation was observed in the ionic liquid (3MP-BF4).     

Comparative studies on performance of radiation-induced and thermal cross-linked ion-exchange membrane for water electrolysis

Radiation-induced and thermal cross-linked sulfonated poly(ether sulfone) (SPS)–sulfonated poly(ether ether ketone) (SPK) composite ion-exchange membranes (SPS/SPK(γ) and SPS/SPK(T), respectively) were prepared. Their performances for water electrolysis were comparatively assessed. Thermal cross-linked membrane (SPS/SPK(T)) showed cross-linking of part functional groups (–SO₃H) and thus deterioration in membrane conductivity. While, radiation-induced cross-linked membrane (SPS/SPK(γ)) avoided any cross-linking between functional groups and thus conductivity. Electrolysis performances of these membranes were evaluated in comparison with Nafion117 membrane. Relatively low current efficiency (CE) for SPS/SPK and SPS/SPK(T) membranes was due to their high mass transfer (water) via electro-osmotic drag, which was negligible for SPS/SPK(γ) membrane. SPS/SPK(γ) membrane exhibited comparable stabilities and water splitting performance with Nafion117 membrane, which revealed its suitability as substitute for electrochemical applications.     

Effect of type of peroxide on cross-linking of poly(l-lactide)

Poly(l-lactide) (PLLA) was cross-linked with various types of peroxides under constant mole ratios of peroxide-derived radicals to PLLA during reactive extrusion. Peroxides were classified into three groups according to their decomposition rates (Group I: fast, Group II: moderate and Group III: slow) and comparisons were performed within each group. Cross-linking behavior was readily understood in terms of free radical efficiency and hydrogen abstraction ability of radicals. In the case of Groups II and III, the weight-average molecular weight (M_w) of cross-linked PLLA increased with overall hydrogen abstraction ability, because slow decomposition caused uniform cross-linking in molten PLLA. In Group I, M_w and gel fraction were higher than other groups despite Group I's lower hydrogen abstraction ability, leading to the conclusion that peroxide decomposition localized in solid PLLA caused partial cross-linking because of rapid decomposition. Furthermore, the efficiency of peroxide-induced cross-linking was investigated using the Charlesby-Pinner equation.     

Synthesis,characterization, thermal stability and compatibility properties of new energetic polymers

Four new cross-linked polymers poly(vinyl m-nitrobenzene)-polyglycidylazides (PVMNB-GAPs) were successfully synthesized using toluene diisocyanate as the cross-linking agent. Their structure was confirmed by their FTIR, UV–Vis, ¹H and ¹³C NMR spectroscopy. Moreover, the thermal properties of cross-linked polymers were evaluated by DTA, TGA and DSC techniques, which confirmed that synthesized polymers exhibited good resistance to thermal decomposition up to 200°C. In addition, their compatibility with the main energetic components of 2,4,6-trinitrotoluene-based melt-cast explosives were also evaluated by the non-isothermal differential thermal analysis method.     

Reversed-phase ion-pair chromatographic method for the determination of nitroprusside in photolyzed solutions

A rapid reversed-phase ion-pair chromatographic method for disodium pentacyanonitrosylferrate(II) (nitroprusside) and its photodegradation products nitrite, nitrate, hexacyanoferrate(II) and hexacyanoferrate(III) is described. For chromatography, phenyl-bonded pellicular silica gel (10 μm) was used with a mobile phase consisting of water (0.005 M tetrabutylammonium phosphate, 0.0011 M n-octylamine, 0.01 M potassium dihydrogenphosphate, pH 7.0) and methanol (0.005 M tetrabutylammonium phosphate, 0.0011 M n-octylamine) (65:35); the detector was set at 220 nm. In 5% (w/v) dextrose solutions, the calibration graph for nitroprusside was linear over the concentration range 10–120 μg ml^?1. A qualitative explanation for the order of retention: hexacyanoferrate(II) < hexacyanoferrate(III) < nitroprusside is given. The method is suitable for the selective determination of nitroprusside in photolyzed infusion solutions (100 μg ml^?1 in aqueous 5% dextrose) and gives an impression of the decomposition products formed.     

Effect of change in the physical properties of water at its peculiar temperature points on the dielectric behavior of sodium polyacrylate

The behavior of sodium polyacrylate is studied via broadband dielectric spectroscopy. The non-Debye response in the frequency range 0.1 Hz–1.0 MHz, the non-Markovian dispersion in the infralow-frequency range, and the anomalies of dielectric permittivity and ac conductivity near “peculiar” temperatures of water (20, 35, 50, and 75°C) are ascertained experimentally. These facts make it possible to assign sodium polyacrylate to disordered media, in which the temperature behavior of dielectric parameters is described by the Kohlrausch–Williams–Watts relaxation function.     

Air-assisted in situ deep eutectic solvent decomposition followed by the solidification of floating organic droplets-liquid-liquid microextraction method for extraction of azole antifungal drugs in biological samples prior to high-performance liquid chromatography

A free dispersive method, air-assisted in situ deep eutectic solvent decomposition followed by the solidification of floating organic droplets liquid-liquid microextraction was indicated in this study. This technique was utilized to simultaneously ascertain some azole antifungal drugs prior to high-performance liquid chromatography. In this research, a quasi-hydrophobic deep eutectic solvent was formed from tetrabutylammonium bromide and 1-dodecanol as an organic solvent at a 1:2 molar ratio. The synthesized deep decomposition in the sample solution caused in situ dispersion of extraction solvent and analytes. Air-assisted enhanced a dispersion condition in the sample solution. 1-Dodecanol as a green option was replaced with typical extraction solvents providing the advantages of a suitable freezing point near room temperature and low density. The effect of important analytical parameters on the extraction recovery of analytes was assessed. Under these optimal conditions, the limits of detection and the limits of quantitation determined were in the range of 0.5–2.8 and 1.5–9 μg/L, for water, urine and plasma samples, respectively. The intra-day and inter-day relative standard deviations (n = 5) were calculated to be 2.9–4.6 and 4.2–8.9%, respectively. The results represented the effectiveness of the developed method for the extraction and determination of analytes in biological samples.     

Synthesis of Fluorinated Polyurethane/Polyacrylate Hybrid Emulsion Initiated by 60Co γ-Ray and Properties of the Latex Film

Based on the solvent-free method, novel fluorinated polyurethane/polyacrylate hybrid emulsions, dodecafluoroheptyl methacrylate (DFMA) as fluorinated monomer, were successfully prepared via emulsion polymerization without traditional emulsifier. For the purpose of increasing the grafting ratio of polyurethane and polyacrylate, ⁶⁰Co γ-ray radiation polymerization had been adopted to enhance the hardness of latex film. The chain structure and polymerization progress were confirmed by the analysis of Fourier transform infrared spectroscopy. The grafting ratio of polymethyl methacrylate and polyurethane was obtained by calculating the ratio of N–H peak integral area and Ph(C=C) peak integral area. The effect of DFMA content on thermal stability, mechanical property and water resistance were investigated systematically by thermal weight loss analysis, tensile strength test, absorbed water ratio and water contact angle.     

Preparation of thermoresponsive core–shell polymeric microspheres and hollow PNIPAM microgels

A reliable and efficient route for preparing thermoresponsive hollow microgels based on cross-linked poly(N-isopropyl acrylamide) (PNIPAM) was developed. Firstly, monodisperse thermoresponsive core–shell microspheres composed of a P(styrene (St)-co-NIPAM) core and a cross-linked PNIPAM shell were prepared by seeded emulsion polymerization using P(St-co-NIPAM) particles as seeds. The size of the P(St-co-NIPAM) core can be conveniently tuned by different dosages of sodium dodecyl sulfate. The thickness of the cross-linked PNIPAM shell can be controlled by varying the dosage of NIPAM in the preparation of PNIAPM shell. Then, hollow PNIPAM microgels were obtained by simply dissolving the P(St-co-NIPAM) core with tetrahydrofuran. The core–shell microspheres and the hollow microgels were characterized by transmission electron microscopy, dynamic light scattering, atomic force microscopy, and Fourier-transform infrared spectroscopy.     

Liquid–liquid equilibria in ternary systems of linear and cross-linked water-soluble polymers

In this study, ternary liquid–liquid equilibrium data of structurally similar linear and cross-linked polymers have been measured in order to elucidate the significance of mixing and elastic effects in sorption of binary liquid mixtures by cross-linked polymers. Dextran, sodium poly(styrene sulfonate), and sodium poly(acrylate) were used as the linear analogues for Sephadex gels and for strong and weak cation exchange resins. Cloud-point and co-existence curves were measured in water/ethanol and water/2-propanol mixtures at 283–343 K and the results were correlated by using a generalized Flory–Huggins model. The mixing parameters of the linear polymers were used to simulate the sorption data in the cross-linked materials and the effect of cross-links was accounted for by a non-ideal elastic model. Good agreement between the simulated and experimental values is obtained, when the chemical heterogeneity and the incomplete functionalization of the cross-linked materials are taken into account. The influence of temperature on the sorption equilibria in cross-linked polymers is also discussed on the basis of the temperature dependence of the cloud-point data.     

Selective adenosine-5'-monophosphate uptake by water-compatible molecularly imprinted polymer

Molecularly imprinted polymers (MIPs) were prepared for adenosine-5′-monophosphate (AMP), a substrate of AMP-activated protein kinase. The template molecule was formed by the vinylphenylboronate diester of adenosine on which 5′-free hydroxide was protected by tert-butyldimethylsilyl group in order to mimic the steric hindrance of the phosphate moiety of AMP. Molecular imprinting was performed by complexing acrylamide and the template in a highly cross-linked polymer. MIPs were tested in batch experiments with aqueous samples of nucleotides and a number of parameters were investigated. The use of tetrabutylammonium hydroxide (TBAH) was necessary to obtain a rebinding of nucleotides on MIP. The adsorption of AMP was optimal in 5 mM ammonium acetate buffer solution pH 9.5 for 30 min, with 30 mM of TBAH. The imprinted polymer was selective for AMP towards others nucleotides or deoxi analogues.     

A facile regioselective ring opening of aziridines to haloamines using tetrabutylammonium halides in the presence of β-cyclodextrin in water

A variety of N-tosylaziridines undergo regioselective ring opening with tetrabutylammonium halides in the presence of β-cyclodextrin in water at pH 4 and room temperature to afford the corresponding haloamines in excellent yields.     

Preparation and characterization of polytetrafluoroethylene‐polyacrylate core–shell nanoparticles

Polytetrafluoroethylene (PTFE)‐polyacrylate core–shell nanoparticles were produced by using PTFE micropowder and acrylate via seeded emulsion polymerization in the presence of fluorosurfactant. The properties of emulsion under various polymerization conditions were investigated and optimized. The chemical composition of the PTFE‐polyacrylate nanoparticles was characterized by Fourier‐transform infrared spectrometry (FTIR). The particle size and core–shell structure of the resulting PTFE‐polyacrylate nanoparticles were confirmed by transmission electron microscopy (TEM). Wettability of the PTFE‐polyacrylate core–shell particles was higher than the pristine PTFE. The formation of this kind of PTFE‐polyacrylate core–shell nanoparticles could improve the compatibility of PTFE with other materials because PTFE is covered by polyacrylate shell, which make them promising in various fields. Copyright © 2007 John Wiley & Sons, Ltd.     

Synthesis and enantiomeric recognition studies of a novel 5,5-dioxophenothiazine-1,9 bis(thiourea) containing glucopyranosyl groups

A novel optically active 5,5-dioxophenothiazine-1,9 bis(thiourea) containing glucopyranosyl groups was synthesized and its enantiomeric recognition properties were examined towards the enantiomers of tetrabutylammonium salts of chiral α-hydroxy and N-protected α-amino acids using UV–vis spectroscopy.     

Polyacrylate/silica nanocomposite materials prepared by sol-gel process

Polyacrylate/silica nanocomposite was prepared by sol-gel process via in situ emulsion polymerization. The influence of the synthetic conditions, such as the ratio of different monomers and the contents of tetraethoxysilane (TEOS), γ-methacryloxypropyltrimethoxysilane (Z-6030), diethanolamine (DAM) and ammonium persulfate (APS) on the physical mechanical properties of polyacrylate/silica nanocomposite was investigated in details. Dynamics Laser Scattering (DLS) indicated that the average diameter of the polyacrylate/silica latex particles (177 nm) was bigger than that of the pure polyacrylate latex particles (105.3 nm), but the ζ potential of polyacrylate/silica was decreased respectively in contrast to that of the polyacrylate. Differential Scanning Calorimeters (DSC) analysis confirmed that the glass transition temperature of polyacrylate/nano-SiO₂ (T_g = −24 °C) was higher than that of polyacrylate (T_g = −36 °C). UV analysis showed that the UV absorbency of polyacrylate/silica was improved evidently in contrast to that of polyacrylate.