A DRIFT spectroscopic study of potassium acetate intercalated mechanochemically activated kaolinite

Kaolinite has been mechanochemically activated by dry grinding for periods of time up to 10 h. The kaolinite was then intercalated with potassium acetate and the changes in the structure followed by DRIFT spectroscopy. Intercalation of the kaolinite with potassium acetate is difficult and only the layers, which remain hydrogen bonded, are intercalated. The mechanochemical activation of the kaolinite may be followed by the loss of intensity of the hydroxyl-stretching vibrations. The intensity of the 3695 and 3619 cm(-1) bands reach a minimum after 10 h of grinding. The observation of a band at 3602 cm(-1) is indicative of the intercalation of the kaolinite with potassium acetate. The degree of intercalation decreases with mechanochemical treatment. The effect of exposure of the intercalated mechanochemically activated kaolinite to moist air results in de-intercalation. The effect of the mechanochemical treatment is loss of layer stacking, which prevents the intercalation of the kaolinite.     

Formation and characterization of mechanochemically generated free lignin radicals from olive seeds

In this study, formation and quantification of mechanochemically generated free radicals of lignin were evaluated after the extraction of lignin from olive seeds and detailed lignin characterization was performed. Lignin was extracted from crushed olive seeds as an insoluble solid using Klason method. Isolated lignin was mechanochemically grinded under cryo conditions using Cryomill and particlesizes were determined by using Zeta Sizer, structural changes were followed by XRD and FTIR-ATR; thermal stabilities were tracked by TGA and DSC. In order to enable solubility demanding studies (such as ¹H‑NMR and GPC), acylation of lignin was accomplished. ESR measurements were completed to prove the nature of the radicals. Free radicals cavenging activity of olive seed lignin was determined and quantified using 2-diphenyl-1-picrylhydrazyl (DPPH) method. Number of created mechanoradicals (per gram of olive seed lignin) was calculated from the corresponding UV‑Vis spectra. Finally, morphological changes of the lignin over cryomilling was evaluated using SEM.     

Synthesis of polyurethane/clay intercalated nanocomposites

 A kind of polyurethane/organophilic montmorillonite (PU/OMT) nanocomposite based on polyether, OMT, phenylmethane diisocyante and diglycol was synthesized and characterized by X-ray diffraction (XRD) and high-resolution electron microscopy (HREM). A polyether/OMT hybrid was first prepared in a nanocomposite form as confirmed by XRD. It was shown that there is a multilayered structure consisting of alternating PU chains stacked with the layers of the silicate layers in the microstructure of the PU/OMT nanocomposite as confirmed by study of the XRD patterns and the HREM images. The contents of the hard segment of PU and OMT had an effect on the basal spacing of the PU/OMT nanocomposite. Received: 29 August 2000 Accepted: 16 February 2001     

Solvent free,palladium catalyzed highly facile synthesis of diaryl disulfides from aryl thiols

An efficient solvent free Pd(pCH₂S)₂dba catalyzed green-chemical strategy for the synthesis of diaryl disulfides from aryl thiols in moderate to excellent yield is reported. Variety of diaryl disulfides were synthesized. The catalyst is recyclable up to four cycles.     

Solvent free synthesis of ynones using magnetically recoverable Copper-ferrite nanoparticles

A general and efficient biogenic CuFe₂O₄ MNP’s catalyzed synthesis of ynones has been reported for the first time. The reaction occurs in solvent free conditions without the use of any harsh conditions. The average diameter of the nanoparticles was found to be 13.07 nm. The advantages of the protocol include heterogeneous catalysis, easy recyclability of the catalyst and short reaction time.     

Solvent free preparation of amidophosphonates from isocyanides

New amidophosphonates are prepared via a two-step Mannich/Ugi one-pot procedure from isocyanides. Aminophosphonates are readily prepared from primary amines, dialkyl phosphites and carbonyl compounds under LiClO₄ catalysis without any solvent. After completion, addition of an isocyanide, an aldehyde and acetic acid give access to phosphono Ugi-type adducts in good to moderate yields.     

Solvent free synthesis of trifluoromethyl tertiary alcohols by cross Aldol reaction

Exceedingly fast preparation of trifluoromethyl tertiary alcohols has been accomplished from methyl ketones and trifluoromethyl ketones under solvent free conditions by cross Aldol reaction. The reaction was achieved in the presence of common inorganic base by grinding method at ambient temperature to give β-trifluoromethyl-β-hydroxyl ketones in high yields (up to 95%).     

Structure of intercalated compounds of graphite fluoride C2FX

Conclusion The results obtained in the present work show that the use of the method proposed in [3] to study the structure of intercalated compounds of graphite fluoride has made it possible to resolve in principle the question of the distribution of the C₂F_X layers along the z axis in these compounds and to determine the nature of the arrangement of the inserted molecules between the layers.In intercalated compounds of stage I with an expanded structure of the filled layer, the molecules of the inserted solvent are distributed chiefly in two layers between the C₂F_x layers, whereas in the compounds with the simple structure they are distributed in one layer.In the intercalated compounds of stage II, the thickness of the unfilled layer is 6 Å, and the thickness of the filled layer coincides with the thickness of the layer in the corresponding inercalated compounds of stage I with the simple structure of the filled layer.The fluorine atoms in C₂F_x are arranged symmetrically on each side of the carbon layer.In the intercalated compounds heated to a temperature of 200°C, the graphite fluoride layers form stacks with a distance of 6.0 Å between the layers.On the basis of the results obtained, it has been suggested that the most probable reason for the strong retention of the inserted component in the intercalated compounds of stage II is the paired linking of the edge sections of the C₂F_x layers.Institute of Inorganic Chemistry, Siberian Branch, Academy of Sciences of the USSR. Translated from Zhurnal Strukturnoi Khimii, Vol. 29, No. 3, pp. 78–83, May–June, 1988.     

Characterization and thermal degradation studies on polyaniline‐intercalated montmorillonite nanocomposites prepared by a solvent‐free mechanochemical route

Polyaniline (PANI)‐montmorillonite (MMT) nanocomposites were prepared by direct intercalation of aniline molecules into MMT galleries, followed by in situ polymerization within the nano‐interlamellar spaces under solvent‐free conditions. The basal spacing of aniline‐intercalated MMT increased gradually up to 1.5 nm with increasing amounts of aniline loaded. This result suggests that aniline molecules were adsorbed by MMT clay and that intercalated aniline likely located perpendicular to the silicate sheets. After polymerization, X‐ray diffraction and Fourier transform infrared analyses confirmed the successful synthesis of PANI chains between the MMT nano‐interlayers. The scanning electron microscopy images indicated that the surface morphologies of PANI–MMTs were strongly different depending on the PANI content. The electrical conductivities of PANI nanocomposite particles in pressed pellets ranged in the order of between 10^?3 and 10^?2 S/cm. UV–vis spectroscopy and doping level measurement were further used to discuss the conductivities of nanocomposites. The thermal stabilities of PANI–MMT nanocomposites were examined by using thermogravimetric‐differential thermal analysis and derivative thermogravimetric analysis, and both analyses consequently demonstrated the improved thermal stabilities of the PANI chains in the nanocomposites as compared to pure PANI. The thermal stabilities of resulting nanocomposites were strongly related to the PANI content, which increased as the PANI content decreased in the nanocomposites. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2705–2714, 2005     

Study of the chemical interaction between mechanochemically synthesized Cu/Bi nanocomposites and liquid gallium

The phase composition and morphology of the diffusion-hardened compound containing Cu/Bi mechanocomposite with nanoscale metals and liquid gallium were examined by synchrotron radiation X-ray diffraction, as well as by atomic force and electron microscopic techniques.     

Rheological evidence for the microstructure of intercalated polymer/layered silicate nanocomposites

The rheological behavior of intercalated polystyrene/layered silicate nanocomposites was investigated. Both storage and loss moduli increased with silicate loading at all frequencies and showed non‐terminal behavior at low frequencies which is a typical behavior of non‐homogeneous systems with ordered microstructures. The rheological behavior in intercalated polystyrene/layered silicate nanocomposite depends not only on the intercalation of polymers, but also on the alignment of silicate layers. Furthermore, the real time intercalation dynamics of polystyrene into the layered silicate, monitored by rheological measurements, were also consistent with our simple quantitative analysis.     

Electrodeposition of layered manganese oxide nanocomposites intercalated with strong and weak polyelectrolytes

Multilayered manganese oxide nanocomposites intercalated with strong (poly(diallyldimethylammonium) chloride, PDDA) and weak (poly(allylamine hydrochloride), PAH) polyelectrolytes can be produced on polycrystalline platinum electrode in a thin film form by a simple, one-step electrochemical route. The process involves a potentiostatic oxidation of aqueous Mn2+ ions at around +1.0 V (vs Ag/AgCl) in the presence of polyelectrolytes. Fully charged PDDA polycations are accommodated tightly in the interlayer space by electrostatic interaction with negative charges on the manganese oxide layers, leading to an interlayer distance of 0.97 nm. The layered film prepared with PAH has a larger polymer content (PAH/Mn molar ratio of 0.98) than that (PDDA/Mn molar ratio of 0.43) made with PDDA because of the smaller charging degree of PAH, exhibiting a larger interlayer distance (1.19 nm). The interlayer PAH contains neutral (-NH2) and positively charged (-NH3(+)) amine groups, and the -NH3(+) groups are associated with Cl- (to generate -NH3(+) Cl- ion pairs) as well as the negatively charged manganese oxide layers. Both polyelectrolytes once incorporated were not ion exchanged with small cations in solution. The layered structure of PDDA/MnO(x) was collapsed during the reduction process in a KCl electrolyte solution, accompanying an expansion of the interlayer as a result of incorporation of K+ ions for charge neutrality. On the contrary, the layered PAH/MnO(x) film showed a good electrochemical response due to the redox reaction of Mn3+/Mn4+ couple with no change in the structure. X-ray photoelectron spectroscopy revealed that, in this case, excess negative charges generated on the manganese oxide layers upon reduction can be balanced by the protons being released from the -NH3(+) Cl- sites in the interlayer PAH; the Cl- anions becoming unnecessary are inevitably excluded from the interlayer, and vice versa upon oxidation.     

Solvent controlled synthesis of CaO-MgO nanocomposites and their application in the photodegradation of organic pollutants of industrial waste

Conventional heating method and hydrothermal method were used for the synthesis of CaO nanoparticles and CaO/MgO nanocomposites under solvent control conditions. Ca(NO₃)₂ and Mg(NO₃)₂ were used as precursors, amyl alcohol as surface directing agent and NaOH as source of OH^?. Different samples of CaO were prepared by conventional heating method in order to investigate the effect of calcination temperature and stirring time. Similarly two different kinds of sets of CaO as well as of CaO/MgO were synthesized under hydrothermal conditions for the investigation of effect of solvent and temperature on catalytic efficiency. Characterizations of these samples were carried out by Powder X-ray Diffractions (XRD), Thermo Gravimetric Analysis (TGA), Field Emission Scanning Electron Microscope (FESEM) Energy dispersive X-ray (EDX) and Fourier Transformed Infrared spectroscopy (FTIR). The synthesized samples of CaO and CaO/MgO were used to degrade methylene blue under UV-Visible conditions, which is an organic pollutant of waste from industries and causing serious health problems. First order data for degradation for methylene blue at λ_max = 665 nm was used to quantify the degradation. Effect of solvent was found to be prominent in all samples. Similarly effect of temperature variation was also pronounced on catalytic efficiency as indicated by value of k.     

Solidlike transition of melt‐intercalated biodegradable polymer/clay nanocomposites

Synthetic biodegradable aliphatic polyester (BAP) intercalated into organoclay was prepared by melt compounding, and its solidlike characteristics were investigated via several rheological test modes: steady shear rotation, oscillation, and creep testing. Structural investigations with X‐ray diffraction and transmission electron spectroscopy were also performed for a better understanding of the characteristic rheological behaviors. The creep, recovery, and stress modulus exhibited a solidlike transition of BAP/clay nanocomposites that depended on the clay content. An increase in the zero shear rate viscosity and a shifting of the crossover point (storage modulus vs loss modulus) to a lower frequency were also observed with increasing clay contents. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2052–2061, 2003     

Solid-state NMR study of intercalated species in poly(epsilon-caprolactone)/clay nanocomposites

The structure and dynamics of surfactant and polymer chains in intercalated poly(epsilon-caprolactone)/clay nanocomposites are characterized by (31)P magic-angle spinning (MAS) and (13)C cross-polarization MAS NMR techniques. To obtain hybrid materials with the low polymer content required for this study, in situ intercalative polymerization was performed by adapting a published procedure. After nanocomposite formation, the chain motion of the surfactant is enhanced in the saponite-based materials but reduced in the Laponite ones. Compared to the starting clay, the trans conformer population of the surfactant hydrocarbon chain in the nanocomposite decreases for the saponite systems. Mobility of the polymer chain is higher in the nanocomposites than in the bulk phase. The charge of the modified saponite does not significantly influence chain mobility in the nanocomposites.     

Synthesis and characterization of polymer/clay nanocomposites by intercalated chain transfer agent

In situ synthesis of poly(methyl methacrylate) (PMMA) and polystyrene (PS) nanocomposites by free radical polymerization using intercalated chain transfer agent (I-CTA) in the layers of montmorillonite (MMT) clay is reported. MMT clay was ion-exchanged with diethyl octyl ammonium ethylmercaptan bromide, which acts both as suitable intercalant and as chain transfer agent. These modified clays were then dispersed in methyl methacrylate (MMA) or styrene (St) monomers in different loading degrees to carry out the in situ free radical polymerization. The intercalation ability of the chain transfer agent and exfoliated nanocomposite structure were evidenced by both X-ray diffraction spectroscopy (XRD) and transmission electron microscopy (TEM). Thermal properties and morphologies of the resultant nanocomposites were also studied.     

Characteristic length of dynamic glass transition based on polymer/clay intercalated nanocomposites

The glass transition is an old physical problem. It has been accepted that there is a cooperatively rearranging region related to dynamic heterogeneity when temperature approaches the glass transition. However, there is no consensus with the characteristic length and the size of cooperatively rearranging region. This paper first employs the clay gallery in polymer/clay intercalated nanocomposites as a confined two-dimensional (2D) space to assess the characteristic length of dynamic glass transition. The five kinds of clays with different d-spacings were used to investigate the confinement effect. Theoretical calculation based on Donth's formula suggests that the characteristic lengths of polyol and polyol-based polyurethane are ∼3.20 and ∼1.45 nm, respectively. The experimental results agree with theoretical prediction using Donth's formula. The characteristic length varies with polymer types.     

Polymerization by amine–metalloid fluoride salts. I. Polymerization of ethyl vinyl ether by anilinium hexafluoroantimonate

Anilinium hexafluoroantimonate is shown to be a very efficient cationic initiator for the polymerization of ethyl vinyl ether from ?78°C to 25°C. The polymer molecular weight varied with temperature and solvent and ranged from very low to near 200,000. After a threshold concentration of catalyst had been obtained, yields were semiquantitative. The catalyst requirement was quite low, near quantitative yields being obtained at concentrations as low as 10^?3 mole-%. Polymer obtained in heptane had a small degree of isotacticity.     

Dynamics of free chains in polymer nanocomposites

The dynamics of entangled polymeric chains in a polymer filled with nanoparticles is studied by means of molecular dynamics simulations of a model system. The primary objective is to study to what extent the reptation of polymers not in direct contact with fillers is modified with respect to the neat material. To this end, two systems are considered: A regular filled material in which the filler-polymer affinity is controlled, and a system in which the beads in contact with the filler at the beginning of the production phase of the simulation are tethered to the filler surface. This second system represents the limit case of long polymer-filler attachment time. In this case attention is focused on the free chains of the melt. The dynamics in the two models is different. In the filled system uniform slowing down for all Rouse modes is observed. The effect varies monotonically with the filler-polymer affinity. Up to saturation, this behavior may be captured by usual models with an effective, affinity-dependent, friction coefficient. In the system with grafted chains, the free chain Rouse dynamics is identical to that in the neat material, except for the longest modes which are significantly slowed down. More interestingly, the dynamics of the free chains depends in a nonmonotonic way on the polymer-filler affinity, although the free chains do not come in direct contact with the filler. This effect is due to small changes in the structure of the polydisperse brush upon modification of the affinity. Specifically, the density of the brush and the amount of interpenetration of free and grafted chains depend on the filler-polymer affinity. The use of a reptation model with modified tube diameter to capture this behavior is discussed.