A series of imidazolium salts having various substituents and functional groups were synthesized and characterized by FTIR and NMR spectroscopy. Organic modification of natural and synthetic layered silicates involving montmorillonite (MMT), laponite (lap), and synthetic mica (mica) was carried out by ion-exchange reaction. The obtained organo-clays were characterized by FTIR and powder X-ray diffraction techniques. Results indicate that these organically modified clays have much higher thermal stabilities compared to their corresponding imidazolium halides. It was also observed from TGA analysis that thermal stability does not depend on the functional group present at the 3-position of the imidazolium salts. These studies strongly supports premise that the removal of halide is necessary to improve the thermal stability of the organo-clay produced. 相似文献
Exfoliation through an ionic exchange reaction of layered silicate clays, including synthetic fluorinated mica (Mica) and natural montmorillonite (MMT), were achieved by using polyvalent amine salts as the intercalating agents. The requisite polyamine was synthesized from the epoxy/amine coupling reaction, involving a trifunctional poly(oxypropylene)-triamine (ca. 440 g/mol Mw) and diglycidyl ether of bisphenol-A. The polyamine was a mixture of oligomeric adducts consisting of multiple amine functionalities and a branched backbone. Partial acidification by HCl addition generated a series of amine salts that affected the intercalation and the expansion of the silicate interlayer in the range of 15.2-60.0 Å XRD d spacing. At the specific acidified ratio (H+/amine = 1/3 equiv ratio), the polyamine salts rendered the clay’s layered structure into randomization. The result was confirmed by using XRD and transmission electronic microscopy (TEM). The hybrids of polyamines and Mica or MMT were blended into epoxy resins and cured into nanocomposites, which exhibited the improvements of thermal stability and hardness. 相似文献
Summary: The organic intercalation of cationic smectite clays is achieved by using alkali salts of alkyl carboxylic acids, instead of using conventional quaternary ammonium salts as ionic exchanging agents. Various organic acid salts, such as CH3(CH2)16COO−Na+, can be incorporated into divalent montmorillonite (M2+‐MMT) with a 30–40 wt.‐% organic embedding and an X‐ray diffraction basal spacing of 43 Å from the pristine 10 Å. The intercalation is generalized for carboxylate salts of different alkyl lengths and for alkali metal ions, including sodium and potassium ions, but is specific for the divalent MMT clay. This new type of organic species for clay modification allows the preparation of organoclays in the absence of quaternary ammonium salts. It is proposed that the organic embedding is driven by the formation of a thermodynamically stable RCOO−/M2+/SiO− complex.
Graphical illustration of the carboxylic acid salt complex with the divalent cations on silicate K10. 相似文献
Poly(methylmetacrylate)/montmorillonite (PMMA)/(MMT) nanocomposites were prepared by one-step in situ intercalative solution polymerization involving simultaneous modification of MMT with quaternary ammonium salts (QAS), polymerization and polymer intercalation. Polymerization proceeded at 70 °C in a mixture of ethanol and water, whereas the nanocomposite was precipitated with only water. Four QAS’s with different alkyl chain lengths, as well as a QAS with an additional acrylic group, were used to study the influence of the type of quaternary ammonium salt on intercalation. The largest extent of intercalation was achieved in nanocomposites with the QAS having one long alkyl (C16) chain. The obtained PMMA/MMT intercalated nanocomposites exhibited a higher glass transition temperature, better thermal stability, and improved solvent resistance than the pure PMMA. 相似文献
Size, morphology, and apparent charge of individual Na-montmorillonite particles of natural MX-80 sodium montmorillonite were investigated in the present study by the use of three coupling methods. In the first part of this work, natural and synthetic montmorillonite clays were studied with atomic force microscopy (AFM) and photo-correlation spectroscopy (PCS). Both techniques exhibit the presence of two clay populations with a high dispersion of the length distribution. Microscopic analysis of the system revealed that clay particles could be reasonably approximated at low concentrations to ellipsoidal tactoids about 1.2 nm high. Average dimensions of the first population were typically 320-400 nm long/250 nm wide and 200-250 nm long/120 nm wide for natural and synthetic clays, respectively. The second population exhibits smaller sizes: 65 and 50 nm long and 35 and 25 nm wide for natural and synthetic clays, respectively. The statistics obtained for natural clay were then verified by PCS experiments on sodium montmorillonite suspensions. Both techniques reveal an important length dispersion. However, the relative proportions of the two kinds of particles could not be established properly because of both lack of statistics and limitations of the employed techniques. In the following part, conductivity measurements were performed on dilute montmorillonite clay suspensions. Raw data were then interpreted with the sizes and morphological information gained in the first part of the present work. The apparent charge of the clay sheets was found to be 8% of the structural charge. 相似文献
Porous PMMA/Na+–montmorillonite (MMT) cation-exchange membranes were successfully prepared by entrapment method in this study. One approach (simple mixing) was to mix commercial PMMA polymer with Na+–MMT clays in solvent for membrane preparation (Membrane A). The other approach (emulsion polymerization) was to synthesize the PMMA/Na+–MMT polymer composite via emulsion polymerization first, followed by membrane casting (Membrane B for Kunipia F clays and Membrane C for PK-802 clays). Membrane morphology and properties were characterized. The thermogravimetric analysis (TGA) verified the near complete incorporation of feed Na+–MMT clays in the PMMA/Na+–MMT composite membranes, while X-ray diffractograms (WXRD) exhibited the slightly enlarged interlayer spacing of Na+–MMT. The range of cation-exchange capacity (CEC) was 9–32 μequiv./47 mm disc. For batch cationic dye adsorption, the best performance was achieved by Membrane B with feed Na+–MMT/MMA (M/P) ratio (w/w) = 0.5 and Membrane C with feed M/P = 0.6, where about 95% Methyl violet adsorption was attained in 2 h. The optimal desorption solution was 1 M KSCN in 80% methanol and its related dye desorption efficiency was 92%. In the flow process using one piece of 47 mm disc of Membrane B (M/P = 0.5), dye solution was recirculated for 6 h and ≥85% dye could be removed. Higher than 94% of dye was desorbed at 1 or 4 mL/min, and the membrane regenerability was proved by successfully performing three consecutive cycles. 相似文献
We have developed a process to incorporate the model protein, bovine serum albumin (BSA), into the layered spacing of swelled mica. By a stepwise intercalation, the sodium form of synthetic fluorinated mica (Mica) was first exchanged with the poly(oxyalkylene)-diamine salts (POA-amine) through an ionic exchange reaction and then the BSA embedment. The first step of the Mica space expansion from the pristine 12 A to 18-93 A was affected by hydrophobic POP-amines (POP2000 of 2000 g/mol and POP4000 of 4000 g/mol M(w)) and the hydrophilic POE2000 that intercalated Na+-Mica to afford different basal spacing (39, 93, and 18 A, respectively). The POA modification was necessary for the BSA intercalation and resulted in an uncompressed form of protein conformation in the layered confinement (XRD d spacing = 60-71 A). For comparison, direct intercalation rendered only low d spacing (30 A), in which BSA was embedded in a compressed conformation. The BSA-mica complexes were characterized by X-ray, TGA, and solution analyses. The stepwise process provides a new method for embedding large protein molecules into the clay layered structure generating protein/layered silicate complexes. 相似文献
It was studied the polymerization of styrene (St) and of butyl acrylate (BuA) in nonionic microemulsions in the presence of a layered alumino silicates, montmorilonit (MMT) type. In time, the latexes separate in two distinct strata, MMT being distributed in the inferior strata where forms aggregates with on order of size bigger than the diameters of nanoparticles of latex. The solid products obtained are nanohybrids of intercalate type whose structural order increases direct proportional with the increase of hydrophobic character of the quaternary ammonium salts used for organophilization of MMT. The presence of nonionic surfactant, nonyl phenol with 25 mols of ethylene oxide, intercalated between the lamellar strata of MMT produces the decrease of thermal stability of hybrids and decreases the glass transition temperature of PSt which is more compatible than PBuA. 相似文献
A study of structural modifications of MPB-07 was undertaken as part of a synthetic program aimed at discovering small molecules with CFTR activation potential. Solid-phase synthesis techniques were used to prepare derivatives of MPB-07 employing the Zincke reaction for the construction of aromatic, quaternary ammonium salts such as those found in 2 or 3. In this transformation, primary amines react with highly electrophilic N-2,4-dinitrophenylpyridinium (DNP) salt 4 to afford pyridinium salt 8 with release of 2,4-dinitroaniline 6. Thus, the reaction of 1-(2,4-dinitrophenyl)pyridinium salts with various polymer-bound amino ethers, followed by cleavage from the resin, delivers the desired salts in good yield and high purity. 相似文献
The synthetic methods for new 2-, 2,2′-, and 3-substituted 4,4′-bis(chloromethyl)biphenyls were developed. Quaternization of them with various amines resulted in a series of new double quaternary ammonium salts containing the biphenyl moiety. The majority of the obtained compounds have a pronounced antifungal and antibacterial activity against the Gram-positive bacteria. 相似文献
Layered silicates were intercalated with comb-branched copolymers consisting of a hydrophobic polystyrene-b-poly(ethylene/butylene)-b-polystyrene (SEBS) backbone and multiple pendants of poly(oxyalkylene) (POA) quaternary ammonium salts. The requisite intercalating agents were synthesized by grafting POA amines on the maleated SEBS. The corresponding SEBS-POA amine salts were found to have two functions, the capability to emulsify toluene/water mixtures to fine particle sizes of 60-70 nm in diameter and to exchange ions with sodium montmorillonite. The resulting silicate hybrids were characterized by X-ray diffraction and transmission electron microscopy. Two types of intercalations with silicate d spacing of 18 and 50 A were obtained, in which the dissimilarity is attributed to disparate polymer incorporations, POA pendants only or the combination of both the SEBS backbone and POA in the gallery. Furthermore, the two conformations of polymer-intercalated silicates are reversibly transformable by varying emulsion conditions, micelle sizes, and solvents. 相似文献
Hybrid materials formed by the combination of a sodium rich Montmorillonite (MMT), with magnetite nanoparticles (40nm, Fe(3)O(4) NPs) coated with Polyethylenimine polymer (PEI 800g/mol or PEI 25000g/mol) were prepared. The intercalation of the magnetite nanoparticles coated with PEI among MMT platelets was achieved by cationic exchange. The resulting materials presented a high degree of exfoliation of the MMT sheets and a good dispersion of Fe(3)O(4) NPs on both the surface and among the layers of MMT. The presence of amine groups in the PEI structure not only aids the exfoliation of the MMT layers, but also gives to the hybrid material the necessary functionality to interact with heavy metals. These hybrid materials were used as magnetic sorbent for the removal of hexavalent chromium from water. The effect that pH, Cr(VI) concentration, and adsorbent material composition have on the Cr(VI) removal efficiency was studied. A complete characterization of the materials was performed. The hybrid materials showed a slight dependence of the removal efficiency with the pH in a wide range (1-9). A maximum amount of adsorption capacity of 8.8mg/g was determined by the Langmuir isotherm. Results show that these hybrid materials can be considered as potential magnetic adsorbent for the Cr(VI) removal from water in a wide range of pH. 相似文献
The synthesis of ionic liquids based upon functionalized quaternary ammonium salts and metal salts of zinc, tin, or iron is demonstrated. The freezing point of these ionic liquids was studied as a function of the quaternary ammonium cation. The complex anions were identified and quantified using mass spectrometry and potentiometry. It is shown that the primary zinc anion is Zn(2)Cl(5)(-) with Zn(3)Cl(7)(-) becoming more abundant in more Lewis basic solutions. Similar results were observed for ionic liquids containing SnCl(2). The surface tension was also measured and was used to explain the high viscosity of the ionic liquids in terms of the large ion:hole size ratio and the small probability of finding a hole of suitable dimensions adjacent to a given ion to permit movement. The phase behavior of a variety of quaternary ammonium halides/ZnCl(2) mixtures is characterized and it is shown that the depression of freezing point is related to the increase in size of the component ions. 相似文献