Ordered Layer Structure Research Articles

Structure, permeability, and rheology of supercritical CO2 dispersed polystyrene-clay nanocomposites

Improvement in clay dispersion and clay-polymer interfacial interactions are keys to producing superior nanocomposites. A supercritical CO2 (scCO2) processing method was utilized to pre-disperse commercial organic clays, for further solvent mixing with polystyrene (PS) to form nanocomposites with significant dispersion and interfacial enhancement. The effect of scCO2 processing on clay pre-dispersion, and clay dispersion and interfacial interaction in nanocomposites were investigated. SEM and WAXD of the clays indicated that after scCO2 processing the clays lose their long region ordered layer structure appreciably, associated with reduction in particle size. WAXD and TEM of the PS/clay nanocomposites showed that the polymer penetrated into the pre-dispersed clay, leading to a disordered intercalated/exfoliated structure with improved interfacial interaction rather than a disordered intercalated structure as seen with as-received clays. Relationships between those structures, rheological and barrier properties were investigated. The scCO2-processed nanocomposites showed a plateau in the low-frequency storage modules and increased complex viscosity, each associated with significant clay dispersion in the nanocomposite. With only 1.09% volume fraction of clay, significant reduction (∼49%) of oxygen permeation was achieved.

Bioinspired Layered Materials with Superior Mechanical Performance

Nature has inspired researchers to construct structures with ordered layers as candidates for new materials with high mechanical performance. As a prominent example, nacre, also known as mother of pearl, consists of a combination of inorganic plates (aragonite calcium carbonate, 95% by volume) and organic macromolecules (elastic biopolymer, 5% by volume) and shows a unique combination of strength and toughness. Investigations of its structure reveal that the hexagonal platelets of calcium carbonate and the amorphous biopolymer are alternatively assembled into the orderly layered structure. The delicate interface between the calcium carbonate and the biopolymer is well defined. Both the building blocks that make up these assembled layers and the interfaces between the inorganic and organic components contribute to the excellent mechanical property of natural nacre. In this Account, we summarize recent research from our group and from others on the design of bioinspired materials composed by layering various primitive materials. We focus particular attention on nanoscale carbon materials. Using several examples, we describe how the use of different combinations of layered materials leads to particular properties. Flattened double-walled carbon nanotubes (FDWCNTs) covalently cross-linked in a thermoset three-dimensional (3D) network produced the materials with the highest strength. The stiffest layered materials were generated from borate orthoester covalent bonding between adjacent graphene oxide (GO) nanosheets, and the toughest layered materials were fabricated with Al2O3 platelets and chitosan via hydrogen bonding. These new building blocks, such as FDWCNTs and GO, and the replication of the elaborate micro-/nanoscale interface of natural nacre have provided many options for developing new high performance artificial materials. The interface designs for bioinspired layered materials are generally categorized into (1) hydrogen bonding, (2) ionic bonding, and (3) covalent bonding. Using these different strategies, we can tune the materials to have specific mechanical characteristics such as high strength, excellent strain resistance, or remarkable toughness. Among these design strategies, hydrogen bonding affords soft interfaces between the inorganic plates and the organic matrix. Covalent cross-linking forms chemical bonds between the inorganic plates and the organic matrix, leading to much stronger interfaces. The interfaces formed by ionic bonding are stronger than those formed by hydrogen bonding but weaker than those formed by covalent bonding.

Surface Heating Fuser with Roller Structure

The surface heating fuser structure has low energy consumption and high heating speed due to its low heat capacity and simple structure. The authors have introduced a surface heating fuser system in NIP 29. The heating material is composed of carbon nano tube and silicon rubber composite, and fabricated with thin film layer structure in order to minimize the heat capacity. A nip supporting member is applied to the heating tube inside slide along the surface of heating tube. But the high friction between the nip support member and the heating tube caused to the limitation of fusing speed and failure of electrical supply unit due to leaked lubricant. In this study, the roller type surface heating fuser structure is proposed. The fusing performance has been predicted by numerical simulation and verified by fabricated proto sample. The high fusing speed and durability of structure is confirmed through the evaluation of fusing system.

The coupling agents’ effects on the BSA intercalated into montmorillonite

The effects of surface modification on montmorillonite (MMT) were illustrated in order to produce the composite material with premium properties. MMT was treated with two coupling agents: glutaraldehyde (GA) and γ-methacryloxy-propyl-trimethoxy silane (KH570). The effects of different coupling agents on MMT and protein interaction were investigated by XRD, FT-IR, TGA, UV-Vis, etc. The results of structure characterization indicated that KH570 modification could change the surface crystal structure of MMT. However, GA reacted with amino groups of Bovine serum albumin (BSA) and the ordered layer structures of MMT were not completely destroyed. Coupling agents could greatly increase the amounts of BSA intercalated and the effect of KH570 is better than that of GA. And, the optimum concentrations of KH570 and GA were 2% and 6%, respectively. The rate of weight loss increased by about 12% after MMT was pretreated with coupling agents. The possible reason is that coupling agent treatment makes the structure of MMT more accessible to protein absorption and helps to stabilize the protein structure. Moreover, the presence of coupling agents can reduce the direct chemical interaction between BSA and MMT, which results in increasing protein desorption.

Three-dimensional ordered SnO2 inverse opals for superior formaldehyde gas-sensing performance

Inverse opals (IO), as a special kind of macroporous material with large surface to volume ratio and ordered layer structure, have great application potential in highly sensitive gas sensing area. In this paper, macroporous SnO2 IO were synthesized by a simply PMMA template method and their porous sizes were controlled ranging of 140–400nm. The performance of the SnO2 IO sensors to formaldehyde (HCHO) gas was systemically studied. The results indicated that the sensing properties of the SnO2 IO sensors to HCHO were highly improved than the traditional sensors, depending strongly on the porous sizes. The response of the SnO2 IO sensors increased gradually with the increase of porous size. The response of the optimum SnO2 sensor was as high as 629 for 100ppm HCHO gas detection and the practical detection limit was as low as 10ppb, which was one of the best levels for the detection of HCHO gas. And more, they also demonstrated fast response dynamics and long time stability.

Ferromagnetic Quantum Critical Point Induced by Tuning the Magnetic Dimensionality of the Heavy-Fermion Iron Oxypnictide Ce(Ru1-xFex)PO

We have performed 31P-NMR measurements of the \(c\)-axis-aligned poly-crystal Ce(Ru1-xFex)PO with a two-dimensional layered structure in order to understand the origin of \(T_{\text{Curie}}\) suppression by Fe substitution. The variation in the magnetic-fluctuation character with respect to \(x\) is investigated from the in-plane and out-of-plane fluctuations and the relationship between the static spin susceptibility and the in-plane fluctuation. It was found that three-dimensional ferromagnetic (FM) correlations are dominant and give rise to the FM ordering in CeRuPO. The out-of plane fluctuations are significantly suppressed with increasing \(x\), and it was revealed that the FM fluctuations become two dimensional near a FM quantum critical point (QCP). Our NMR results strongly suggest that a unique FM QCP in Ce(Ru1-xFex)PO is induced by the suppression of the magnetic correlations along the \(c\)-axis, which is a different mechanism from that presumed in heavy-fermion compounds.

Triphenylene-modified chitosan: novel high efficient sorbent for cationic and anionic dyes

The first example of triphenylene-modified chitosan 4 was prepared by reacting chitosan with triphenylene aldehyde derivative 3. Its structure and morphology was characterized by elemental analysis, 1H NMR, FTIR, XRD, SEM and AFM image. The triphenylene units in Tp-chitosan 4 appended on the skeleton of chitosan and possessed orderly layered structure. Adsorption experiments of Tp-chitosan 4 indicated that it possessed excellent adsorption capacities for both cationic and anionic dyes [Orange G sodium salt, Brilliant ponceau 5R, Victoria blue B (VB), Crystal violet (CV), Neutral red (NR) and Methylene blue]. The highest adsorption capacities for CV, VB and NR were 5.612, 5.353 and 5.375 mmol/g, respectively. Adsorption kinetics and isotherms analysis showed that the adsorption processes obeyed pseudo second-order model and the Langmuir isotherm equation. The adsorption processes were exothermic and spontaneous. The best pH values for adsorption were pH = 6–8.

Formation of Flat, Homogeneous Surfaces of Organized Molecular Films of Three-Armed Polymerizable Amphiphiles with Metal-Scavenging Properties

Surface complexing (i.e., metal-bridged polymerization in this study) of a three-armed amphiphilic compound with metal-scavenging properties has been investigated using the surface pressure-area (π-A) isotherms of a Langmuir monolayer from the subphase. Inductively coupled plasma mass spectrometry (ICP-MS) was also carried out on eluted solutions from corresponding multilayers of the solid. Furthermore, the molecular arrangement and surface morphology of organized molecular films of the resultant comb polymer were estimated by in-plane and out-of-plane X-ray diffraction (XRD) and by atomic force microscopy. From an analysis of the wide-angle X-ray diffraction of the corresponding monomer in the bulk, the long hydrocarbon chains are observed to pack hexagonally in the solid state. Compared to their monolayer on distilled water as the subphase, a polymerized monolayer on a buffer solution containing Cd(2+) ions is remarkably expanded at 15 °C. From ICP-MS and IR measurements, it is found that this monolayer stoichiometrically contains Cd(2+) ions on the -SH group. It is found by XRD that highly ordered layer structures and regular 2D lattices are constructed in the organized molecular films of the Cd-bridged comb polymer. Furthermore, the surface morphology of Langmuir-Blodgett films fabricated from the monolayers on a buffer solution containing Cd(2+) and Pd(2+) shows flat and smooth domains upon metal scavenging and polymerization.

Influence of preparation method on structure, morphology, and electrochemical performance of spherical Li[Ni0.5Mn0.3Co0.2]O2

Spherical Li[Ni0.5Mn0.3Co0.2]O2 was prepared by both the continuous hydroxide co-precipitation method and continuous carbonate co-precipitation method under different calcined temperatures. The physical properties and electrochemical behaviors of Li[Ni0.5Mn0.3Co0.2]O2 prepared by two methods were characterized by X-ray diffraction, scanning electron microscope, and electrochemical measurements. It has been found that different preparation methods will result in the differences in the morphology (shape, particle size, and tap density), structure stability, and the electrochemical characteristics (shape of initial charge/discharge curve, cycle stability, and rate capability) of the final product Li[Ni0.5Mn0.3Co0.2]O2. The physical and electrochemical properties of the spherical Li[Ni0.5Mn0.3Co0.2]O2 prepared by continuous hydroxide co-precipitation is apparently superior to the one prepared by continuous carbonate co-precipitation method. The optimal sample prepared by continuous hydroxide co-precipitation at 820 °C exhibits a hexagonally ordered layer structure, high special discharge capacity, good capacity retention, and excellent rate capability. It delivers high initial discharge capacity of 175.2 mAh g−1 at 0.2 C rate between 3.0 and 4.3 V, and the capacity retention of 98.8 % can be maintained after 50 cycles. While the voltage range is broadened up to 2.5 and 4.6 V vs. Li+/Li, the special discharge capacities at 0.2 C, 0.5 C, 1 C, 2 C, 5 C, and 10 C rates are as high as 214.3, 205.0, 198.3, 183.3, 160.1 and 135.2 mAh g−1, respectively.

The biaxial lamello-columnar liquid crystalline structure of a tetrathiafulvalene sanidic molecule

A macroscopically oriented lamello-columnar mesophase was obtained from a newly designed and synthesized symmetric tetrathiafulvalene-based molecule (symTTF11) containing four flexible alkyl chains chemically attached to the periphery of TTF mesogens (L. Wang, et al., J. Mater. Chem., 2011, 21, 60), and its phase behaviors and physical properties were investigated by the combined experimental techniques. Based on the experimental results and structure analyses, it was revealed that there are two ordered columnar phases below the isotropic phase: a columnar crystalline phase (ColK) and a columnar smectic liquid crystal phase (ColL). From two-dimensional wide angle X-ray diffraction patterns of the macroscopically oriented samples, phase structures of ColK and ColL were identified and their biaxial molecular packing structures were also proposed. Since the assembled symTTF11 columns were well organized in the ordered layer structures over a macroscopic domain, symTTF11 exhibited a good charge carrier mobility in the ColL phase.

New SmCG Phases in a Hydrogen-Bonded Bent-Core Liquid Crystal Featuring a Branched Siloxane Terminal Group

In this study, we synthesized three analogous bent-core molecules, a hydrogen-bonded complex and a covalent-bonded compound with branched siloxane units (H-SiO and C-SiO, respectively) and a hydrogen-bonded complex with an alkyl unit (H-Alk), and investigated the effects of the hydrogen bonding and branched siloxane terminal units on their mesomorphic properties. The covalent-bonded compound C-SiO and the hydrogen-bonded complex H-Alk exhibited typical SmCP phases; in contrast, the hydrogen-bonded complex H-SiO exhibited a series of general tilt smectic (SmCG) phases with highly ordered layer structures (i.e., SmC̃G(2)P(F)-USmCG(2)P(A)-SmCG(2)P(F)-SmCGP(F) upon cooling). During the SmCG-type phase transition process, a 2D-modulated ribbon structure transferred into highly ordered layers via undulated layers, as the hydrogen-bonding strength increased with reduced temperatures. As the SmCG domains were aligned under dc electric fields, a gradual decrease in the leaning angle from ca. 60° to 50° (while the tilt angle kept at ca. 31°) could be determined by in situ wide-angle X-ray scattering (WAXS). Combined with Fourier transform infrared and Raman spectroscopic data, our results suggest that the change in the leaning angle was governed by the competition of the hydrogen bonds and microsegregation of siloxane units within the bilayer structure of the hydrogen-bonded complex H-SiO. In addition, the ferroelectric-(antiferroelectric)-ferroelectric transitions proven by the switching current responses in the SmCG-type phases of H-SiO reveal that the polar switching occurred through collective rotations around the long axis of H-SiO. Therefore, novel SmCG phases with a series of highly ordered 2D-structures were induced by the effects of the hydrogen bonding and branched terminal siloxane unit in the bent-core hydrogen-bonded LC complex H-SiO.

“Clicking” graphite oxide sheets with well-defined polystyrenes: A new Strategy to control the layer thickness

Polystyrene (PS) graft graphite oxide (GO) was synthesized by Cu (I)-catalyzed 1, 3-dipolar cycloaddition (“click” coupling) of azido modified graphite oxide with well-defined, alkyne-terminated polystyrene. This method produced PS blocks graft on GO surface, while ordered layer structure between GO sheets was observed for the first time in GO/Polymer composite. The layered structure was characterized and confirmed by 1D X-ray diffraction (XRD) and atomic force microscopy (AFM), and the layer thickness was observed to be controlled with intercalated PS length between GO layers.

Formation and structure of organized molecular films for organo‐modified montmorillonite and mixed monolayer behavior with poly(L‐lactide)

AbstractWe investigated the molecular orientation and surface morphology of organized molecular films with regard to solid‐state structures for organo‐modified montmorillonites by surface pressure‐area (π − A) isotherm, in‐plane and out‐of plane X‐ray diffraction (XRD), and atomic force microscopy (AFM). From the results of out‐of plane XRD, formation of highly ordered layer structure was confirmed in these clay Langmuir‐Blodgett (LB) film. Further, two‐dimensional lattice of long alkyl chain of organo‐modified parts packed hexagonally or orthorhombically in the films. Surface morphology of Z‐type monolayers on solid of organo‐modified montmorillonites indicates heterogeneous modification ratio in montmorillonite surface by AFM observation. In addition, monolayer behavior on the water surface and mesoscopic morphological formation on solid of mixed films of organo‐modified montmorillonite and poly‐(L‐lactide) (PLLA) were investigated by π − A isotherm and AFM. Collapsed surface pressures are independent on the mixed ratio, and indicate almost constant value in their isotherms. This tendency is a peculiarity of immiscible system. From the result of AFM observation, phase separated structure was confirmed in mesoscopic scales. This phase separated morphology remarkably varied with mixed ratio. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers

Preparation and characterization of Langmuir–Blodgett films of endohedral metallofullerene Gd@C 82

Monolayer Langmuir–Blodgett (LB) films of metallofullerene Gd@C 82 mixed with stearic acid (Gd@C 82/SA) were deposited onto mica substrates from the air/water interface. The structural characteristics of these films were studied by atomic force microscopy (AFM) and contact angle (CA). The results showed that the metallofullerene Langmuir–Blodgett (LB) films with SA (Gd@C 82/SA) were easily fabricated by vertical dipping method compared to the pure metallofullerene film. When the molar ratio of SA:Gd@C 82 was up to 4:1, the corresponding LB films exhibited a uniform and ordered layer structure.

Microstructural Changes in LiNi0.8Co0.15Al0.05O2 Positive Electrode Material during the First Cycle

The microstructure of LiNi0.8Co0.15Al0.05O2 positive electrode material before and after the first cycle was investigated by scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS). STEM and EELS analysis shows that, before cycling, there are very thin layers of material at grain boundaries that contain a small amount of transition metal ions (particularly Ni) on Li sites. After the first cycle, the thickness of some grain boundary layers increases significantly, accompanied by formation of microcracks at grain boundaries. Also, from the grain interior to the grain boundary, the structure gradually changes from an ordered layer structure (α-NaFeO2-type) to a partially ordered structure and then to a disordered rock-salt structure. We posit that these microstructural changes are primarily responsible for the irreversible capacity during the first cycle.

Preparation and Structural Phase Transitions of Silver Laurate

Thermal behaviors, compositions and structures of silver laurate prepared in wateralcohol system with double jet method has been investigated via DSC, FTIR, XRD and SEM, respectively. Silver nitrate, sodium hydroxide and lauric acid were used as reactants and PVP as protective agent. Results show that the highly ordered layer structures of as prepared samples were weakened at 173oC and 212oC and then decomposed at 238oC. The morphology changed from fiber-like to lamellar when the silver laurate was calcined at 212oC.

High rate charge–discharge properties of LiNi 1/3Co 1/3Mn 1/3O 2 synthesized via a low temperature solid-state method

A simple solid-state method has been successfully applied to synthesize a LiNi 1/3Co 1/3Mn 1/3O 2 cathode material. Powder X-ray diffraction results indicate that the suitable temperature of synthesizing LiNi 1/3Co 1/3Mn 1/3O 2 is 850–900 °C, lower than proposed in other reports. The charge–discharge tests are performed at 1000 mAg −1 in a potential range of 2.5–4.5 V. The average full-charge time is within 6 min. The discharge capacity of the material is significantly influenced by raw materials and reaction temperature. The sample calcined at 900 °C using α-MnO 2 nanorods as the raw material shows the best electrochemical performance. It is attributed to the highly ordered layer structure and the lowest degree of cation mixing, being improved by nanorod MnO 2, which facilitates the diffusion of Li + in the compounds. Thus, this simple solid-state method using α-MnO 2 nanorods as the raw material is a good route for synthesizing LiNi 1/3Co 1/3Mn 1/3O 2 as the cathode material of lithium power batteries.

Highly Ordered and Stable Layered “Polymer Nanosheets” Constructed with Amorphous Side Chains and π−π Stacking of Functional Groups in Ternary Comb Copolymers

We have developed a highly stable, layered structure for ternary copolymers in Langmuir-Blodgett (LB) films at a nanometer scale, with substantial durability over the long-term. In these ternary copolymer LB films, amorphous side chains support the layered structure, and the distance between the layers is controlled at the nanometer scale by the composition of hydrogenated and fluorinated side chains. In the present study, the fine structures of newly synthesized ternary comb copolymers with a carbazole ring in the solid state and molecular orientations in the LB films were investigated using wide-angle X-ray diffraction (WAXD), small-angle X-ray scattering (SAXS), surface pressure-area (pi-A) isotherms, in-plane and out-of-plane X-ray diffraction (XRD), and atomic force microscopy (AFM). The WAXD results identified two short-spacing peaks related to the formation of the subcells for both the fluorinated and hydrogenated side chains. Further, SAXS measurements indicated that these ternary copolymers formed a highly ordered layer structure. In addition, monolayers on the water surface of these ternary copolymers were highly condensed. From the results of in-plane XRD and AFM, it was determined that the side chains and side-chain crystals could not form phase-separated structures in two-dimensional films. These structural features may result from enhancement of pi-pi interactions between the arranged carbazole rings. The side chains of the copolymers in the two-dimensional films are apparently in a miscible state, and monolayers form a homogeneous amorphous surface because of cancellation of differences in van der Waals forces between the two types of side chains. As a result, formation of a highly ordered layer structure in copolymer films having substantial durability over the long term is realized because amorphous side chains support the layer structure in the LB multilayers. Further, control of long spacing at a subnanometer level becomes possible due to changes in the tilt angle of the side chains, depending on their fluorocarbon content.

Anionic Poly(p-Phenylenevinylene)/Layered Double Hydroxide Ordered Ultrathin Films with Multiple Quantum Well Structure: A Combined Experimental and Theoretical Study

The sulfonated phenylenevinylene polyanion derivate (APPV) and exfoliated Mg-Al-layered double hydroxide (LDH) monolayers were alternatively assembled into ordered ultrathin films (UTFs) employing a layer-by-layer method, which shows uniform yellow luminescence. UV-vis absorption and fluorescence spectroscopy present a stepwise and regular growth of the UTFs upon increasing deposited cycles. X-ray diffraction, atomic force microscopy, and scanning electron microscopy demonstrate that the UTFs are orderly periodical layered structure with a thickness of 3.3-3.5 nm per bilayer. The APPV/LDH UTFs exhibit well-defined polarized photoemission characteristic with the maximum luminescence anisotropy of approximately 0.3. Moreover, the UTF exhibit longer fluorescence lifetime (3-3.85-fold) and higher photostability than the drop-casting APPV film under UV irradiation, suggesting that the existence of a LDH monolayer enhances the optical performance of the APPV polyanion. A combination study of electrochemistry and periodic density functional theory was used to investigate the electronic structure of the APPV/LDH system, illustrating that the APPV/LDH UTF is a kind of organic-inorganic hybrid multiple quantum well (MQW) structure with a low band energy of 1.7-1.8 eV, where the valence electrons of APPV can be confined into the energy wells formed by the LDH monolayers effectively. Therefore, this work not only gives a feasible method for fabricating a luminescence ultrathin film but also provides a detailed understanding of the geometric and electronic structures of photoactive polyanions confined between the LDH monolayers.

Surface Morphological Changes in Monolayers of Aromatic Polyamides Containing Various N-Alkyl Side Chains

We synthesized new aromatic polyamides (poly-(N-alkylated benzamides), abbrev. PABA(n)) having both a rigid main chain and a flexible side chain with different lengths. We investigated the solid-state structures, that is, the molecular orientation and surface morphology, of organized molecular films of PABA(n) by performing surface pressure-area (pi-A) isotherm, in-plane and out-of plane X-ray diffraction (XRD), polarized infrared spectroscopy, and atomic force microscopy (AFM) measurements. The solid-state structure of poly-(N-methyl benzamide) (PABA(1)) belonged to the monoclinic system, whereas PABA(3), PABA(4), and PABA(5) showed an orthorhombic packing pattern. PABA(7) and PABA(8) formed amorphous polymers. In the case of PABA(17), a two-dimensional hexagonal lattice was formed as a subcell consisting of side chains. These polymer monolayers were highly condensed on a water surface at 15 degrees C. Out-of-plane XRD measurement results showed that the PABA(1), PABA(3), PABA(4), and PABA(5) multilayers showed large periodicities of 50-60 A. From AFM observation results, it was found that these aromatic polyamides formed single particle layers of hydrophilic groups localized at the bottom of the particles. On the other hand, PABA(7) and PABA(8) monolayers showed irregularity and exhibited shapeless morphologies. In addition, an organized molecular film of PABA(17) formed a highly ordered layer structure (periodicity of 30 A) and a giant circular domain (diameter of 20 nm) made of a side chain crystal. The PABA(17) monolayer showed a hexagonal packing pattern formed due to van der Waals interaction between the flexible side chains. From these experimental findings, it was concluded that the polymer synthesis method employed in the present study can be directly used to control the crystal structure (the third order structure of polymers), molecular arrangement, and surface morphologies of polymer monolayers.