Quaternary Alkylammonium Research Articles

PMMA-clay nanocomposite materials: Free-radically grafting of PMMA onto organophilic montmorillonite (20A)

This paper reports the grafting of poly(methyl methacrylate) (PMMA) onto organophilic montmorillonite (Cloisite 20). Cloisite 20A was reacted with vinyltrichlorosilane to replace the edge hydroxyl groups of the clay with a vinyl moiety. Under the reaction condition, the exchange of quaternary alkylammonium cations with H+ ions was prevented and only the silanol groups on the edge of the clay reacted with vinyltrichlorosilane. The radical polymerization of the product with methyl methacrylate as a vinyl monomer led to the chemical grafting of PMMA onto the montmorillonite surface. Chemical grafting of the polymer onto Cloisite 20A was confirmed by Infrared (IR) spectroscopy after Soxhelt extraction. The interlayer and surface changes to the clay in the prepared nanocomposite materials and the grafted nano-particles were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The intercalated nanocomposites were obtained for clay contents up to 5%. The nanocomposites were examined by thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMTA). Nanocomposites exhibit a higher glass transition temperature and improved thermal properties than neat PMMA due to an interaction between the PMMA matrix and PMMA-grafted clay particles.

A general approach to rubber–montmorillonite nanocomposites: Intercalation of stearic acid

The effect of stearic acid on the properties of different rubbers/montmorillonite composites was studied. We used alkyl quaternary ammonium modified montmorillonite (organo-montmorillonite), which was additionally modified with stearic acid. Premixed with the montmorillonite, the stearic acid expanded the clay mineral layers, thus permitting the rubber molecules to be more easily intercalated into the montmorillonite. We used several kinds of rubbers with different polarities and molecular structures. Both the X-ray diffraction and infrared spectroscopy studies indicated that the stearic acid propped up interlayer space allowing the intercalation of the rubber chains. Measurement of the physical and dynamic mechanical properties, along with studies of the composite morphology by transmission electron microscopy, very clearly showed that mixing the montmorillonite clay with stearic acid yielded various rubber nanocomposites with a high amount of intercalated and exfoliated montmorillonite particles. Either complete intercalation or increased nanostructure formation yielded as compared to the standard rubber–clay mineral composites prepared with a normal dose (2 parts per hundred of rubber) of stearic acid, can be achieved by adding a large amount of stearic acid (10 parts per hundred of rubber in our case) to non-polar rubbers (e.g. natural rubber (NR), ethylene propylene rubber (EPDM), etc.) that are not known to form totally exfoliated structures by simple melt mixing of montmorillonite and rubber.

Thermal Stability of Organoclays: Effects of Duration and Atmosphere of Isothermal Heating on Iodide Sorption

Heating periods necessary to destroy iodide sorption capacity of the quaternary (alkyl) ammonium and phosphonium modified bentonites were determined using iodide sorption batches. For this purpose, prior to the batches the studied organoclays were isothermally heated in air in the temperature ranges of 110-180 °C and 160-300 °C, respectively. The temperature dependence of the heating periods was found to follow the Arrhenius relationship, which allowed a determination of Arrhenius parameters for the reaction leading to the loss of the iodide sorption capacity of a bentonite modified by CP(+) (cetylpyridinium), BE(+) (benzethonium), CTMA(+) (cetyltrimethylammonium), or TPP(+) (tetraphenylphosphonium) surfactant. At 160 °C, the thermal stability of the iodide sorption capacity of TPP(+)-bentonite is much higher than that of the second most stable CTMA(+)-bentonite (80 days vs 5 days). However, the obtained Arrhenius parameters predict that CTMA(+)-bentonite becomes the most stable one as the heating temperature decreases to 40 °C with iodide sorption still available for ∼12000 years as compared to ∼8000 years for TPP(+)-bentonite. Heating of the organoclays in a N(2)-atmosphere (<70 ppm O(2)) at 160 °C revealed that the strong deficit of molecular oxygen in the contacting atmosphere resulted in a strong increase of their thermal stability. For CTMA(+)-bentonite, this increase is equivalent to the stability increase due to a decrease of the heating temperature by ∼20 °C (from 160 °C to ∼140 °C). Accordingly, the iodide sorption capacity of CTMA(+)-bentonite at a heating temperature of 40 °C is predicted to be retained for ∼350,000 years in the absence of molecular oxygen.

Chiral quaternary alkylammonium ionic liquid [Pro-dabco][BF 4]: as a recyclable and highly efficient organocatalyst for asymmetric Michael addition reactions

A novel series of chiral quaternary ammonium ionic liquids have been synthesized and shown to be very effective catalysts for the asymmetric Michael addition reactions of ketones and aldehydes to nitroolefins with excellent yields (up to 100%), diastereoselectivities ( syn/ anti = 99:1), and enantioselectivities (up to 97%). The catalytic system, an ionic liquid organocatalyst in [Bmim][BF 4], could be reused five times without a significant loss in catalytic activity or stereoselectivity.

Polymer–clay nanocomposites: Free-radical grafting of polyacrylamide onto organophilic montmorillonite

This paper is an account of the experiments on grafting polyacrylamide onto organophilic montmorillonite. Cloisite 20A was reacted with vinyltrichlorosilane to replace the edge hydroxyl groups of the clay with a vinyl moiety. Since the reaction liberates HCl, it was performed in the presence of sodium hydrogencarbonate to prevent the exchange of quaternary alkyl ammonium cations with H + ions. Only the silanol groups on the edge of the clay react with vinyltrichlorosilane. The product maintained the same basal spacing as the precursor. The radical polymerization of the product with acrylamide as a vinyl monomer leads to chemical grafting of polyacrylamide onto montmorillonite surface. The homopolymer formed during polymerization was Soxhelt extracted from the grafted organoclay. Chemical grafting of the polymer onto Cloisite 20A was confirmed by IR spectroscopy. The interlayer and surface changes of the clay in the prepared nanocomposite materials and the grafted nano-particles were studied by XRD and SEM. Intercalated nanocomposites were obtained for clay contents of 3–7% and agglomeration occurred at higher clay loadings. The nanocomposites were studied by thermogravimertic analysis (TGA) and dynamic mechanical analysis (DMTA).

Synthesis and characterization of novel anion exchange membranes based on imidazolium-type ionic liquid for alkaline fuel cells

Novel anion exchange membranes based on the copolymers of 1-allyl-3-methylimidazolium chloride (AmimCl) ionic liquid either with methyl methacrylate (MMA) or butyl methacrylate (BMA) have been prepared via free radical polymerization. The structures and characteristic properties of the membranes are studied. It is found that the hydroxyl ionic conductivity of the synthesized membrane can reach 3.33 × 10 −2 S cm −1 in deionized water at 30 °C. The methanol permeability is less than 10 −9 mol cm 2 s −1 even at 60 °C. These membranes with imidazolium salt functional groups exhibit superior stability both chemically and thermally as well compared to the alkyl quaternary ammonium functionalized polymers. Therefore, the membranes have good perspectives and great potential for alkaline fuel cell applications.

Effect of Alkyl Properties and Head Groups of Cationic Surfactants on Retention of Cesium by Organoclays

Cationic surfactants modified clays exhibit high sorptive capability toward anionic radionuclides but retention of cationic radionuclides was concurrently reduced. In this study, organoclays were synthesized by intercalating a variety of primary/quaternary alkylammonium species (NH(2)R/(CH(3))(3)N(+)RBr(-), where R = benzyl, dodecyl, and octadecyl) into bentonite MX-80. The effect of surfactant's properties on enhancing or limiting cationic sorption capability was investigated by performing Cs sorption experiments. Experimental results were analyzed using the MINEQL+ software by considering Cs uptake by structural and edge sorption sites. Bentonites that were intercalated with primary alkylammonium surfactants had a higher sorptive capacity than those intercalated with quaternary alkylammonium surfactants. Samples intercalated with octadecyl-bearing surfactants had the lowest sorption rate. XRD and FTIR analyses revealed that each organoclay had a characteristic arrangement of alkyl chains. The cation retention of organoclays was dominated by the extent of hydrophobic interactions affected by the local distribution and arrangement of surfactants. The intercalated primary alkylammoniun surfactants tended to transform into local clusters with a high packing density, leaving more structural sites available for Cs uptake. In contrast, the NH(3)R(+)-surfactants tended to form a denser monolayer over clay surface, inhibiting the retention of Cs at structural sites.

Mutations in the K+-Channel KcsA Toward Kir Channels Alter Salt-Induced Clusterization and Blockade by Quaternary Alkylammonium Ions

Protein aggregation is a result of malfunction in protein folding, assembly, and transport, caused by protein mutation and/or changes in the cell environment, thus triggering many human diseases. We have shown that bacterial K(+)-channel KcsA, which acts as a representative model for ion channels, forms salt-induced large conductive complexes in a particular environment. In the present study, we investigated the effects of point mutations in the selectivity filter of KcsA on intrinsic stability, aggregation, and channel blocking behavior. First, we found that a low sodium chloride concentration in potassium-containing media induced fast transfer of single channels to a planar lipid bilayer. Second, increasing the sodium chloride concentration drastically increased the total channel current, indicating enhanced vesicle fusion and transfer of multiple channels to a planar lipid bilayer. However, such complexes exhibited high conductance as well as higher open probability compared to the unmodified KcsA behavior shown previously. Interestingly, the affinity of aggregated complexes for larger symmetric quaternary alkylammonium ions (QAs) was found to be much higher than that for tetraethylammonium, a classical blocker of the K(+) channel. Based on these findings, we propose that mutant channel complexes exhibit larger pore dimensions, thus resembling more the topological properties of voltage-gated and inwardly rectifying K(+) channels.

Reinforcement of diene elastomers by organically modified layered silicates

AbstractNanocomposites were prepared based on diene rubbers and layered clays modified with an alkyl quaternary ammonium cation (organoclay). A diene rubber, either polybutadiene, or synthetic or naturally occurring polyisoprene or styrene-butadiene copolymer, was melt blended with either a preformed organoclay or with a mixture of pristine clay and ammonium cation. Besides isolated lamellae, nanocomposites showed the presence of crystalline organoclays with intercalated organic layers made only by low molecular mass substances, essentially the ammonium cation, and no evidences for the intercalation of polymer chains were observed. Dynamic-mechanical properties of sulphur cured compounds with carbon black as the main filler and a minor amount of organoclay were investigated. The organoclay was found to bring about a reduction of Mooney viscosity, an increase of storage modulus at low temperature as well as an increase of thermoplasticity.

Natural and modified clays from Morocco as sorbents of ionizable herbicides in aqueous medium

The capacities of two Moroccan clays, one of them swelling and the other non-swelling, as sorbents of three ionisable pesticides: terbutryn (basic), dicamba (anionic) and paraquat (cationic) were studied. Sorption was studied on natural and modified clays with three quaternary alkyl ammonium cations of different long-chain, octadecyltrimethylammonium (ODTMA), octyltrimethylammonium (OTMA) and tetramethylammonium (TMA). Freundlich or Langmuir models were used to obtain sorption parameters. Sorption of terbutryn and dicamba by ODTMA-clays was always higher than by natural clays. Distribution coefficients (Kd) of these modified clays increased 55–128-fold (terbutryn), and 1.4–8.6-fold (dicamba) respect to the natural clays. In contrast, sorption of terbutryn by the TMA-clays and of dicamba by TMA- and OTMA-clays was lower than for natural clays. Sorption coefficients of paraquat by natural clays were similar or higher than those obtained with modified clays. In general, the sorption of herbicides was higher by swelling clay than by non-swelling clay. The results point out that the Moroccan clays studied may be used as sorbents of cationic pesticides in their natural form and of basic or even anionic herbicides when modified with long-chain organic cations in barrier technologies to enhance the immobilization of herbicides and to prevent the contamination of surface and ground water.

KPF 6 dissolved in propylene carbonate as an electrolyte for activated carbon/graphite capacitors

KPF 6 dissolved in propylene carbonate (PC) has been proposed as an electrolyte for activated carbon (AC)/graphite capacitors. The electrochemical performance of AC/graphite capacitor has been tested in XPF 6-PC or XBF 4-PC electrolytes (X stands for alkali or quaternary alkyl ammonium cations). The AC/graphite capacitor using KPF 6-PC electrolyte shows an excellent cycle-ability compared with other electrolytes containing alkali ions. The big decomposition of the PC solvent at the AC negative electrode is considerably suppressed in the case of KPF 6-PC, which fact has been correlated with the mild solvation of K + by PC solvent. The relationship between the ionic radius of cation and the corresponding specific capacitance of AC negative electrode also proves that PC-solvated K + ions are adsorbed on AC electrode instead of naked K + ions.

Syntheses of PAM microgel surfacely covered with alkyl quaternary ammonium surfactant/Keggin‐type polyoxometalate complexes

AbstractThe composite microspheres of poly(lacrylamide) microgels (PAM) surfacely covered with [2‐(methacryloyloxy)ethyl]dodecyldimethylammonium (MEDDAB)‐tungstophosphate (HPW) complexes (MEDDAB‐HPW) were synthesized by using ion‐exchange reaction between MEDDAB located within the porous PAM microgels and HPW in aqueous solution. The morphology and component of the composite microspheres were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis, respectively. The results indicated that PAM/MEDDAB‐HPW composite microsphere with different hierarchical surface structures could be obtained by controlling the weight ratio of MEDDAB to HPW in the microgels and cross‐linking degree of PAM microgels. Although the surface morphologies of the composite microspheres prepared in different conditions were different, a general feature was that the composite microspheres have the core‐shell structure and the wrinkly surface covered with the particles of MEDDAB‐HPW complexes. The formation of the wrinkly surface is attributed to the difference in shrinkage between inside and outside of PAM microgel frameworks due to deposition of MEDDAB‐HPW on the surface, and the formation of MEDDAB‐HPW small particles originates from the reaction between MEDDAB aggregation and HPW. For this composite microsphere, PAM hydrogel core is suitable to store water‐soluble substances, and the shell composed of the surfactant/Keggin‐type polyoxometalate complexes is not only amphiphilic but also catalytic. Additionally, PAM/MEDDAB‐HPW composite microspheres with big size and MEDDAB‐HPW particles with small size make the composite microspheres not only easy for separation but also beneficial for catalysis. This material provides an example to construct microreactors with new structure used in diphase catalytic reaction. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Characterization of complexation of poly (N-isopropylacrylamide-co-2-(dimethylamino) ethyl methacrylate) thermoresponsive cationic nanogels with salmon sperm DNA

Thermoresponsive cationic nanogel (TCNG) networks based on N-isopropylacrylamide (NIPAM), 2-(dimethylamino)ethyl methacrylate (DMAEMA), and quaternary alkyl ammonium halide salts of DMAEMA (DMAEMAQ) were synthesized by dispersion polymerization technique. The thermoresponsive properties of TCNGs and TCNG-salmon sperm DNA (sasDNA) polyplexes were characterized in aqueous media of various pH and ionic strength. P[NIPAM] and P[NIPAM/DMAEMA] TCNGs exhibited sharp volume phase transition (VPT) in water at critical temperatures (T(c)) of 32 degrees C and 36 degrees C, respectively. Quaternized P[NIPAM/DMAEMAQ] TCNGs did not undergo sharp VPT up to 50 degrees C. The VPT of uncomplexed TCNGs were sensitive to the ionic composition and ionic strength of salts in solution, but were insensitive to pH in the range 5.0 to 7.4. The VPT of P[NIPAM/DMAEMAQ]/sasDNA diminished in magnitude with increasing W(p)/W(d) suggesting greater compaction of the polyplexes. The distinct phase-transition properties of P[NIPAM/DMAEMA]/sasDNA and P[NIPAM/DMAEMAQ]/sasDNA polyplexes were attributed to the condensing capability of polycations and to differences in the spatial distribution of structural charges in quaternized and nonquaternized networks. The findings demonstrate that stable TCNGs can be prepared with controllable responsive properties determined by the nature of the cationic charge incorporated and may have potential as vehicles for DNA delivery.

Phosphonium‐based layered silicate—Poly(ethylene terephthalate) nanocomposites: Stability, thermal and mechanical properties

AbstractPET‐clay nanocomposites were prepared using alkyl quaternary ammonium and phosphonium modified clays by melt‐mixing at 280°C using a micro twin screw extruder. The latter clays were prepared by synthesizing phosphonium surfactants using a simple one‐step method followed by a cation exchange reaction. The onset temperature of decomposition (Tonset) for phosphonium clays (&gt;300°C) was found to be significantly higher than that of ammonium clays (around 240°C). The clay modified with a lower concentration (0.8 meq) of phosphonium surfactant showed a higher Tonset as compared to the clay modified with a higher concentration (1.5 meq) of surfactants. Nanocomposites prepared with octadecyltriphenyl phosphonium (C18P) modified clay showed a higher extent of polymer intercalation as compared with benzyltriphenylphosphonium (BTP) and dodecyltriphenylphosphonium (C12P) modified clays. The nanocomposites prepared with ammonium clays showed a significant decrease in the molecular weight of PET during processing due to thermal degradation of ammonium surfactants. This resulted in a substantial decrease in the mechanical properties. The molecular weight of PET was not considerably reduced during processing upon addition of phosphonium clay. The nanocomposites prepared using phosphonium clays showed an improvement in thermal properties as compared with ammonium clay‐based nanocomposites. Tonset increased significantly in the phosphonium clay‐based nanocomposites and was higher for nanocomposites which contained clay modified with lower amount of surfactant. The tensile strength decreased slightly; however, the modulus showed a significant improvement upon addition of phosphonium clays, as compared with PET. Elongation at break decreased sharply with clay. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

In situ x-ray diffraction studies of alkyl quaternary ammonium montmorillonite in a CO2 environment

An in situ study was conducted using an x-ray diffractometer and a specially designed high pressure cell to examine the effects of carbon dioxide at different pressures and temperatures on three different modified montmorillonite species. These organoclays possessed organic pillars of quaternary ammonium surfactant with either one, two, or three long (C(16)-C(18)) alkyl chains attached to expand the galleries of the clay mineral. The three clay species were tested between 50 degrees C and 200 degrees C with carbon dioxide pressures between 0.1 and 8.4 MPa. Under these conditions, the three organoclays exhibited marked differences in their basal spacing depending on the surfactant used. The physical state of the intercalated surfactant was found to be of critical importance, with no changes in basal spacing noted until the organic component began to melt, in spite of CO(2) being present. A pressure effect was also noted which delayed melting of the surfactants as the pressure of the system increased. In all cases, further cation exchange with residual sodium cation present in the galleries was observed in the presence of CO(2) and above the melting state of the surfactant. The study included examination of the effect of rapid depressurization on the clay structure, which produced only a small change in basal spacing.

STUDIES ON THE MORPHOLOGICAL, THERMAL AND RESISTIVITY PROPERTIES OF RECYCLED POLY (ETHYLENE TEREPHTHALATE) COMPOSITES WITH NANOCLAY FILLERS

Nanocomposites based on polymer-clay mixtures are a growing area of interest due to their potential in flexible applications. In this study, new nanocomposite materials were produced from the components of recycled thermoplastic as the matrix and montmorillonite as the filler by using a co-rotating twin screw extruder. During this study, recycled Poly(Ethylene Terephthalate), rPET, was mixed with organically modified quaternary alkyl ammonium montmorillonite in the contents of 1, 2, and 5 weight %. Three types of clays were evaluated during the studies. For comparison, 2 weight % clay containing samples were prepared with three different clay types, Cloisite 15A, 25A, 30B.Even though, 2wt% Cloisite25A shows better mechanical properties, 2 wt% Cloisite30B is better in respect of electrical properties.

Polysiloxane cationic biocides with imidazolium salt (ImS) groups, synthesis and antibacterial properties

Novel polysiloxanes with pendant biocidal N, N′-dialkylimidazolium salt (ImS) groups were synthesized and compared with polysiloxanes bearing conventional biocidal quaternary ammonium salt (QAS) groups. The bacteriostatic power of these polymers was tested and compared under the same conditions in aqueous solution against two common strains of Gram positive bacteria and three strains of Gram negative bacteria. These new ImS containing polymers exhibited high antibacterial potency against all bacteria studied, similar to those substituted with QAS groups. The advantage of the imidazolium substituted polysiloxane stems from its higher thermal stability, as compared with the quaternary alkylammonium functionalized polymer, as demonstrated by thermogravimetric studies.

Synthesis and characterisation of coating polyurethane cationomers containing quaternary ammonium alkyl groups derived from built-in alkyl bromides

Polyurethane cationomers were synthesised in the reaction of 4,4′-methylenebis(phenyl isocyanate) with polyoxypropylene glycol (M = 450) and N-methyl diethanolamine. Amine segments were built-in to the urethane–isocyanate prepolymer in the reaction with 1-bromoalkanes (C2–C10), and then they were converted to alkyl-ammonium cations. The obtained isocyanate prepolymers were then extended in the aqueous medium. That yielded stable aqueous dispersions which were applied on the surfaces of test poly(tetrafluoroethylene) plates. After evaporation of water, the dispersions formed thin polymer coatings. 1H and 13C NMR spectral methods were employed to confirm chemical structures of synthesised cationomers. Based on 1H NMR and IR spectra, the factors κ and α1 or α1 were calculated, which represented the polarity level of the obtained cationomers. The differential scanning calorimetry method revealed decline of Tg for the hard urethane and urea segments from 60 °C to 46 °C when the number of carbon atoms increased in the alkyl radical attached to the ammonium cation. Changes were discussed in the surface free energy (SFE) and its components, as calculated independently according to the methods suggested by van Oss-Good and by Owens–Wendt, in relation to chemical structures of cationomers. The growing length (from C2 to C10) of the alkyl radical attached to the N atom in the cationomer chain was found to reduce the value of SFE of the polymer coating from 46 to 28 mJ/m2. That is caused by gradual weakening of long-range interactions, within which the highest share is taken by dispersion interactions.

Defect-Free Copper Filling Using Nonisothermal Electroless Deposition with Fluorocarbon Surfactant

Electroless copper bottom-up filling of patterned substrates using nonisothermal deposition (NITD) with the addition of adequate surfactant was demonstrated. Combining the inhibitive ability of adequate surfactant with the higher driving force of NITD method, superfill of vias or trenches using only one inhibitor in the copper damascene of integrated circuits (ICs) was achieved. We tested several commercial surfactant agents and found that fluorinated alkyl quaternary ammonium iodides (FC) is best compatible to our NITD method. Void-free copper-filled features can be obtained by introducing the surfactant FC into the electroless bath of NITD. Furthermore, using our method, the conductivity of copper film was not negatively affected. We conclude that the surfactant FC combined with NITD method is very promising for the applications in filling trenches and vias with copper films in the IC industry.

A short review on surface chemical aspects of Li batteries: A key for a good performance

We review herein several important aspects of surface chemistry in Li-ion batteries, and discuss the use of ionic liquids (ILs) for rechargeable Li batteries. We explored the suitability of ILs for 5 V cathodes and Li-graphite anodes. Some advantages of the use of ILs to attenuate the thermal behavior of delithiated cathode materials are demonstrated. We also report briefly on a comparative study of the following cathode materials: LiNi 0.5Mn 0.5O 2; LiNi 0.33Mn 0.33Co 0.33O 2; LiNi 0.4Mn 0.4Co 0.2O 2; LiNi 0.8Co 0.15Al 0.05O 2 and LiMnPO 4, in standard electrolyte solutions based on mixtures of alkyl carbonates and LiPF 6. We also discuss aging, rate capability, cycle life and surface chemistry of these cathode materials. The techniques applied included electrochemical measurements, e.g., XRD, HRTEM, Raman spectroscopy, XPS and FTIR spectroscopy. We found that ILs based on cyclic quaternary alkyl ammonium cations may provide much better electrolyte solutions for 5 V cathodes than standard electrolyte solutions, while being quite suitable for Li-graphite electrodes. All the lithiated transition metal oxides studied (as mentioned above) develop unique surface chemistry during aging and cycling due to the acid-base and nucleophilic reactions of their surface oxygen anions. LiMn 0.33Ni 0.33Co 0.33O 2 has the highest rate capability compared to all the other above-mentioned cathode materials. Cathodes comprising nanometric size carbon-coated LiMnPO 4 produced by HPL demonstrate a better rate capability than LiNi 0.5Mn 0.5O 2 and LiNi 0.8Co 0.15Al 0.05O 2 cathodes. The former material seems to be the least surface reactive with alkyl carbonates/LiPF 6 solutions, among all the cathode materials explored herein.