超吸水中国粘土/聚丙烯酸复合材料的制备与表征

本文采用共聚合法,以过硫酸钾作为发剂,N-N-亚甲基双丙烯酰胺作为交联剂,亚硫酸钠作为催化剂,合成了不同组成的SAPC样品系列.对比不同样品,找出中国粘土含量和丙烯酸含量对吸水和保水能力的影响.与原始粘土相比,中国粘土在SAPC中的层间距离有所扩大.SAPC中粘土含量对吸水性的影响表明,在45%含量以下,水的吸收率随粘土含量的增加而增加,而粘土含量的进一步增加降低了水的吸收性.在不同丙烯酸重量百分比样品中,最佳吸收率在丙烯酸重量百分比25%～35%之间.所得聚合物复合材料具有约190 g/g的高吸水性.     

Swelling Properties and Environmental Responsiveness of Superabsorbent Composite Based on Starch-G-Poly Acrylic Acid/Organo-Zeolite

Star-g-poly (acrylic acid)/organo-zeolite 4A (S-g-PAA/OZ) superabsorbent composite was prepared by grafting partially neutralized acrylic acid onto starch in the presence of organo-zeolite 4A (OZ) as an inorganic component. The morphology was characterized with scanning electron microscopy (SEM). Energy dispersive spectrometer (EDS) analysis revealed the fine distribution of OZ in superabsorbent composite. The swelling kinetics of the composites were characterized by means of a Schott's second-order model. The effect of OZ concentration in the composite on the water absorbency and swelling behavior were tested. The swelling properties of the composites were evaluated in various environments; pH, salinity, temperature, urea solution, and solvent-water mixtures. The activation energy (ΔE) for water during the swelling process was also determined through Arrhenius plots. The results showed that the proper amount of OZ was beneficial for improvement of the water absorbent capacity and the initial swelling rate in distilled water. The optimum prepared composite with 10 wt % OZ, possessed the maximum water absorption (511g/g) in distilled water and (521 g/g) in 0.1 wt % urea solution. The results inferred that S-g-PAA/OZ superabsorbent composite can be exploited for agriculture and medical applications.     

Intercalation of Iron Atoms under Graphene Formed on Silicon Carbide

The intercalation of iron under a graphene monolayer grown on 4H-SiC(0001) is studied. The experiments have been carried out in situ under conditions of ultrahigh vacuum by low-energy electron diffraction, high-energy-resolution photoelectron spectroscopy using synchrotron radiation, and near carbon K-edge X-ray absorption spectroscopy. The deposited iron film thicknesses have been varied within 0.1–2 nm and the sample temperatures from room temperature to 700°C. It is shown that the intercalation process begins at temperatures higher than ~350°C. In this case, it is found that intercalated iron atoms are localized not only between graphene and a buffer layer coating SiC, but also under the buffer layer itself. The optimal conditions of the intercalation are realized in the range 400–500°C, because, at higher temperatures, the system becomes unstable due to the chemical interaction of the intercalated iron with silicon carbide. The inertness of the intercalated films to action of oxygen is demonstrated.

     

Room-Temperature Mid-, and Far-Infrared Absorption and Electrical Properties of Intercalated GaSe and TlInS2 Crystals

We report room-temperature measurements of the mid- and far-IR absorption throughout the 400 – 4000 cm⁻¹ and 10 – 700 cm⁻¹ spectral ranges and the resistivity of layered p-GaSe and p-TlInS2 intercalated with Li⁺. Intercalation was performed by immersing Bridgman grown crystals in 0.5 M solutions of LiCl in distilled water at ambient conditions. The crystal structure and the stoichiometry of the grown crystals were determined by X-ray diffraction and XRF methods. It is shown that intercalation does not change the frequency of the IR-, and Raman active low-frequency “rigid layer” mode (GaSe), the space symmetry group or the lattice parameters of the crystals. It was found that for both crystals, the resistivity versus time dependencies are nearly the same. Three ranges in the resistivity-intercalation time dependencies were explained qualitatively. The resistivity increase due to intercalation was explained by assuming that the intercalated lithium ions act as ionized donors and compensate the host p-type crystal. The highest degree of compensation for GaSe and TlInS₂ crystals was achieved after intercalation during 12 and 10 days, respectively.     

Intercalation of graphite and hexagonal boron nitride by lithium

Although graphite and hexagonal form of BN (h-BN) are isoelectronic and have very similar lattice structures, it has been very difficult to intercalate h-BN while there are hundreds of intercalation compounds of graphite. We have done a comparative first principles investigation of lithium intercalation of graphite and hexagonal boron nitride to provide clues for the difficulty of h-BN intercalation. In particular lattice structure, cohesive energy, formation enthalpy, charge transfer and electronic structure of both intercalation compounds are calculated in the density functional theory framework with local density approximation to the exchange-correlation energy. The calculated formation enthalpy of the considered forms of Li intercalated h-BN is found to be positive which rules out h-BN intercalation without externally supplied energy. Also, the Li(BN)₃ form of Li-intercalated h-BN is found to have a large electronic density of states at the Fermi level and an interlayer state that crosses Fermi level at the zone center; these properties make it an interesting material to investigate the role of interlayer states in the superconductivity of alkali intercalated layered structures. The most pronounced change in the charge distribution of the intercalated compounds is found to be charge transfer from the planar σ states to the π states.     

Immobilization of kojic acid in ZnAl-hydrotalcite like compounds

Kojic acid (KOJ) is a melanin synthesis inhibitor widely used as skin lightening agent in topical preparations. Unfortunately it is easily susceptible to photo-oxidation, phenomenon responsible for chemical and organoleptic modifications. The aim of this work was the intercalation of KOJ in hydrotalcite-like compounds (HTlc) in order to stabilize KOJ and to reduce its photolability. Hydrotalcite containing Zn and Al (ZnAl-HTlc) was used as host to obtain the final compound ZnAl-HTlc-KOJ. The intercalation was carried out, after many attempts, by ionic exchange mechanism by means of the strong base EtO^? in anhydrous ethanol/dimethylsulfoxide (DMSO) mixture as solvent in order to generate KOJ^? anions. The final product was characterized by the X-ray powder diffraction (XRPD), FT-IR spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and elemental analysis. The intercalated compound was formulated in a siliconic water free self-emulsifying ointment and the in vitro release profile was evaluated. All samples (intercalation compound and its formulation) were submitted also to spectrophotometric assays in order to evaluate the matrix protective effect towards ultraviolet rays.     

Light Auxiliary Hydrogen‐Evolution Catalyst Based on Uniformly Pt Nanoparticles Decorated Molybdenum Sulfide Hybrids

The electrocatalytic splitting of water via hydrogen evolution reaction (HER) is one of the most efficient technologies for hydrogen production, while the massive consumption of precious Pt‐based catalysts hinders its commercialization, bringing an urgent task to explore low‐cost and earth‐abundant alternatives. Herein, a cost‐efficient system composed of metal Pt/molybdenum disulphide (MoS₂) nanosheets hybrids for the HER by auxiliary of solar light is reported. The uniformly Pt nanoparticle decorated MoS₂ sheets can be easily obtained under hydrothermal condition using oleylamine as capping agent and N,N‐dimethylmethanamide (DMF) as intercalation molecule for MoS₂ exfoliation. The Pt/MoS₂ hybrid shows a significantly enhanced HER activity compared with bare MoS₂ due to enhancing conductivity and reducing overpotential by electron transport between Pt and MoS₂. As a result, a Tafel slope of 38 mV per decade is obtained, suggesting a highly efficient Volmer–Heyrovsky reaction of hydrogen evolution.     

In situ conduction ESR and theoretical studies of graphite intercalation by nitric acid

Results of an in situ conduction electron-spin resonance (CESR) study of HNO, molecule intercalation into highly oriented pyrolytic graphite (HOPG) plate with width being comparable with the graphite skin-depth governed by thec-axis conductivity are presented. The changes in the graphite CESR signal line shape, intensity and linewidth and the stepwise changes both of intensity and linewidth of CESR signal of intercalated sample were clearly detected during this reaction. Under the assumption that the graphite CESR signal evolution is caused by the advance of a boundary separating the intercalated and nonintercalated HOPG, the average value of spin reorientation probability during the collision of current carriers with this interface and the diffusion coefficient of nitric acid into the HOPG plate were extracted from experimental data. With the chemical potential versus intercalation time proposed by the authors for the experimental conditions, the stepwise changes of the CESR signal intensity of intercalated sample was calculated theoretically.     

Modification of the electronic structure of graphene by intercalation of iron and silicon atoms

The ab initio calculations of the electronic structure of low-dimensional graphene–iron–nickel and graphene–silicon–iron systems were carried out using the density functional theory. For the graphene–Fe–Ni(111) system, band structures for different spin projections and total densities of valence electrons are determined. The energy position of the Dirac cone caused by the p _z states of graphene depends weakly on the number of iron layers intercalated into the interlayer gap between nickel and graphene. For the graphene–Si–Fe(111) system, the most advantageous positions of silicon atoms on iron are determined. The intercalation of silicon under graphene leads to a sharp decrease in the interaction of carbon atoms with the substrate and largely restores the electronic properties of free graphene.

     

Gallate-Zn-Al-layered double hydroxide as an intercalated compound with new controlled release formulation of anticarcinogenic agent

A new organic-clay material, in which the organic moiety is intercalated into the inorganic interlayer, was prepared using gallate anion (GA) as a guest, and Zn-Al-layered double hydroxide, as clay host. The ion-exchange technique was found to be effective for the intercalation process in the formation of the compound. Although the basal spacings of the LDH and its intercalated product were fairly similar, FTIR, CHNS and TGA/DTG results indicated that the GA was actually intercalated into the interlayer of the host in parallel orientation. The resulting nanostructure material possessed a well ordered layered structure with 42.2% GA loading (w/w). The release of the anion from the interlayer of the intercalated compound was found to be of controlled manner, governed by the first order kinetic and it was also concentration dependent. The material has potential as a nano-storage of anticarcenogenic agent with controlled delivery capability.     

Properties of Poly(Lactic Acid)/ Organo-Montmorillonite Nanocomposites Prepared by Solution Intercalation

Poly(lactic acid)/organo-montmorillonite (PLA/OMMT) nanocomposite films were prepared through solution intercalation using dichloromethane as solvent. X-ray diffraction indicated that organo-montmorillonite (OMMT) was well intercalated and the interlayer spacing d increased by 0.94–1.47 nm. Transmission Electron Microscopy showed that a majority of OMMT was fully exfoliated and uniformly dispersed in the PLA matrix at low filler loading, whereas more intercalated tactoids and aggregates of OMMT existed at high loading. The crystallinity of PLA was hardly changed with the addition of OMMT. Additionally, CO₂ permeability and water vapor transmission rate of the composite films were reduced with increasing content of OMMT. At 5 wt% OMMT loading, CO₂ permeability and water vapor transmission rate were reduced by 75.8% and 23.9%, respectively. The tensile strength (TS) and Young's modulus of the PLA/OMMT nanocomposites were first enhanced, and then decreased with increasing content of OMMT. Compared with pure PLA, a 83.8% increase in the Young's modulus and a 76.0% improvement in TS were obtained with the addition of 3 wt% OMMT.     

Synthesis and Water Absorbency Properties of Hydrogels Based on Lotus Root Starch

In order to increase the added value of lotus root starch, a new-style hydrogel was prepared by grafting copolymerization by acrylic acid (AA), 2-acrylamide-2-methylpropanesulfonic acid (AMPS), K₂S₂O₈, and N,N′- methylene-bis-acrylamide (MBA) in presence of lotus root starch. The molecular structure was characterized by Fourier transform infrared spectroscopy (FTIR). The different conditions that had an influence on the water absorbency are discussed, such as the ratio of initiator to monomers, the ratio of cross-linker to monomers, the mass ratio of AA and AMPS, the lotus root starch's mass, and the reaction temperature. For the product having the optimal water absorbency of 476 g/g, its water absorption kinetics diffusion model and equation were also researched. The material is friendly to the environment and is suggested to have significant potential to be used in various fields.     

Intercalation of [Pt(NH3)4]2+ ions into layered sodium silicate magadiite: a useful method to enhance their stabilisation in a highly dispersed state

Al-free layered sodium silicate magadiite has been used as the host material for the stabilisation of [Pt(NH₃)₄]²⁺ ions via intercalation and/or ion-exchange reactions. The stabilisation of Pt(NH₃)₄]²⁺ ions in between the layers of Na-magadiite was confirmed by thermogravimetric analysis (TGA), where increased decomposition temperatures were observed for the intercalated materials. The intercalation behaviour of Na-magadiite was evident from the significant uptake of Pt ions (22.2 wt%). When silica gel was used as the host matrix, negligible uptake of Pt ions (1.3 wt%) was noticed. The X-ray diffraction (XRD) measurements revealed no appreciable change in the basal spacing of the intercalated materials. Nevertheless, the decrease in the intensity of the 001 peak with increasing Pt loadings (from 13.0 to 22.2 wt%) substantiated the intercalation of [Pt(NH₃)₄]²⁺ ions within the interlayer spaces of Na-magadiite. The transmission electron microscopy (TEM) studies of the intercalated materials revealed that [Pt(NH₃)₄]²⁺ ions were homogeneously intercalated in the magadiite matrix, ranging from 2 to 3 nm. Subsequent calcination of the intercalated materials at 600 °C in air led to the formation of Pt nanoparticles supported on silica. The results of XRD and TEM indicated that Pt nanoparticles were highly dispersed on the silica support and were in the range of 5–12 nm. Moreover, chemical analyses confirmed the high loading of Pt on silica in agreement with the TGA results.     

Synthesis and properties of HgI2 intercalation of Bi2Sr2CaCu2Oy superconductor

Polycrystalline or single crystals of HgI₂ intercalated Bi₂Sr₂CaCu₂O_y (Bi2212) have been synthesized and their properties have been studied together with those of HgBr₂ intercalates. Single crystals of HgI₂ intercalated Bi2212 were synthesized by a stepwise intercalation method using iodine intercalate as a secondary host material. These could not be obtained through direct intercalation methods by which polycrystalline sample were obtained. From ac susceptibility and resistivity measurements, superconducting onset temperature (T_con) for polycrystalline HgI₂ intercalate was found to be 82 K which was higher than that of the host (75 K). On the other hand, T_con for single crystal HgI₂ intercalate was shown to be 79–80 K which is lower than that of host (95–97 K). The effect of HgI₂ or HgBr₂ intercalation on T_c tried discussion from the view point of hole doping and interblock coupling effect.     

On the thermodynamic driving force for polymer intercalation in smectite clays

The view that the intercalation of a polymer in an unmodified smectite clay is driven by the entropic increase that results from displacement of adsorbed water is re-assessed in the light of experiments that show rapid melt intercalation into a clay that has been heat-treated to remove gallery water. Dehydrated smectite clays with collapsed layers take up poly(ethylene glycol) from the melt in only 1?ks or from aqueous solution in under 18?ks, re-establishing the basal plane spacing to that for intercalation in untreated clay, 1.8?nm. Differential scanning calorimetry showed that the intercalation of poly(ethylene glycol) into montmorillonite is exothermic with an enthalpy change of ?153?J?g^?1 based on the intercalated polymer and the heat of wetting for the internal surfaces of montmorillonite by poly(ethylene glycol) is ?0.08?J?m^?2. These results confirm the observation of re-expansion of heat-treated clays and imply that the reduction in free energy on intercalation results from a significant enthalpic change as well as an entropic change for clays with interlayer water, and primarily from an enthalpic change for clay in the absence of water.     

Thermo-Sensitivity of poly-N-isopropylacrylamide with Statistically Introduced D,L-Allylglycine Betainic Units

Abstract

Statistical copolymers of N-isopropylacrylamide containing 2.2 – 2.7?mol % D,L-allylglycine were synthesized. The sample with 2.2?mol % allylglycine and molar mass 320000?g/mol was studied using light scattering and turbidimetry while heated in water and water–salt solutions. Temperature dependencies of light scattering intensity and optical transmission as well as hydrodynamic size and composition of the scattering entities were obtained in a wide range of pH. The onset temperatures of phase separation were independent of pH; however, in the basic pH region the phase transition was widened as compared to the neutral and acid media. It was shown that a small content of allylglycine results in a different thermoresponsive behavior of the copolymer as compared with N-isopropylacrylamide homopolymer. The addition of a physiological amount of NaCl shifts the copolymer thermo-sensitivity toward lower temperatures.     

Evaluation of an alternative modification route for layered silicates and synthesis of poly(styrene) layered silicate nanocomposites by in-situ suspension polymerisation

The organically modified montmorillonites (o-MMT) used in this study were prepared in a semi-solid state in molten long chain alkyl (hydrogenated tallow (HT) or stearyl) dimethyl/aryl ammonium chloride intercalant (quat), within a Brabender Plasticorder W50E chamber. The effect of quat level and structure was investigated using WAXS, FTIR (DRIFTS) and solvent swelling/dispersion viscosity studies. It was found that mono-stearyl (or HT) quats were the most suitable intercalants for the in-situ polymerised PS matrix nanocomposites produced. The distearyl (or HT) quats generally led to reduced interfacial effects in the composites and reduced toluene dispersion viscosity due to the close proximity of long alkyl tails within the molecules facilitating their self-assembly into ordered arrays, which were difficult for toluene to penetrate (toluene was used as a probe to gauge compatibility with styrene). Substitution of a benzyl group (for a methyl) led to increased compatibility with styrene/toluene, though the detrimental effect of two long alkyl groups was not overcome. PS matrix nanocomposites have been formed via in-situ free radical suspension polymerisation of styrene/organo-montmorillonite (o-MMT) dispersions. These composites displayed evidence of large interfacial area relative to the volume fraction of montorillonite added; this was manifested as a reduction in melt flow rate, broadening of the molar mass distribution (increase in M _w) and an increase in thermal stability, relative to the unfilled matrix. However, wide angle X-ray scattering (WAXS) patterns of the composites revealed a strong (001) reflection (d = 3.3–3.4 nm) together with clear (002) and (003) reflections. Therefore a mixed intercalated/flocculated morphology, with no significant exfoliation into single platelets, was indicated.     

Electrical conductivity and chemical bond of graphite intercalation compound with fluorine and metal fluoride

Graphite intercalation compounds with fluorine and metal fluoride (MgF₂ or CuF₂) were prepared from petroleum coke and pyrolytic graphite. With progress in the intercalation reaction, the first stage compound with identity period 9.4 Å changed to another structure of identity period 10.7 Å. It was found from ESCA measurements that the chemical interaction between intercalated fluorine and carbon was similar to the covalent bond around the surface and slightly ionic in the bulk. The maximum electrical conductivities in the direction of the ab-axis were (1.9–2.0) × 10⁵ (ωcm)^-1, which were 10–13 times that of the original pyrolytic graphite.     

Intercalation of papain enzyme into hydrotalcite type layered double hydroxide

Intercalation of proteolytic enzyme papain into hydrotalcite type LDH structure was achieved by controlled co-precipitation at pH=9.0 in the presence of papain. Characterization of the MgAl–papain–LDH phase was carried out using X-ray powder diffraction (XRD), elemental analysis, infrared spectroscopy (IR) and thermogravimetry (TG). According to XRD, papain was successfully intercalated. The d-value for the basal spacing of MgAl–papain–LDH was found at ～5.3 nm. Consequently, original papain (hydrodynamic diameter ～7.2 nm) attains a compressed conformation during intercalation.Formation of MgAl–papain–LDH was confirmed by elemental analysis and transmission electron microscopy (TEM). Under SEM, MgAl–papain–LDH phases appear as nanothin platelets which are intergrown to flower-like aggregates. Steric size and activity of the enzyme was retained after deintercalation from MgAl–LDH framework, as was evidenced by light scattering and UV/vis measurements. Thus, papain is not denatured during intercalation, and LDH is a suitable host structure which can provide a time-controlled release of the biomolecule.     

Intercalation of metals and silicon at the interface of epitaxial graphene and its substrates

Intercalations of metals and silicon between epitaxial graphene and its substrates are reviewed. For metal intercala- tion, seven different metals have been successfully intercalated at the interface of graphene/Ru（O001） and form different intercalated structures. Meanwhile, graphene maintains its original high quality after the intercalation and shows features of weakened interaction with the substrate. For silicon intercalation, two systems, graphene on Ru（O001） and on Ir（l I 1）, have been investigated. In both cases, graphene preserves its high quality and regains its original superlative properties after the silicon intercalation. More importantly, we demonstrate that thicker silicon layers can be intercalated at the interface, which allows the atomic control of the distance between graphene and the metal substrates. These results show the great potential of the intercalation method as a non-damaging approach to decouple epitaxial graphene from its substrates and even form a dielectric layer for future electronic applications.