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We have obtained a new class of porous silica with good structural order and additional corrugated nanopores clustered around the primary mesopores from the co-condensation of TEOS and adamantylphenol-grafted trimethoxysilane (adam-graft SQ) using a triblock Pluronic P123 (EO20PO70EO20, Mw = 5800) copolymer as a structure-directing agent. Thermally activated removal of pore-generating moieties (i.e., adamantylphenol groups) in adam-graft SQ involves the generation of secondary micro-to-small mesopores, while the block copolymer template generates 2D-hexagonal mesopores. We found that the mesostructural characteristics and the generation of secondary indented pores right next to the mesopores can be tailored by the addition order of the two silica precursors (TEOS and adam-graft SQ), varying the molar ratio between TEOS and adam-graft SQ in the starting sol mixture, and the degree of silica polymerization. The increase in the hexagonal unit cell parameters is attributed to the increment of pore size originating from the removal of adamantylphenol moieties. It is believed that the hydrophobicity of adamantylphenol groups plays a key role in its selective incorporation into the region near the PPO core blocks and the subsequent generation of corrugated pores along the silica channels resulting in the increase of pore diameter. [ABSTRACT FROM AUTHOR]

The fracture toughness of interfaces between a sulfonated alkyl side-chain graft copolymer and a soft acrylic random copolymer containing acrylic acid monomers was investigated with a probe test method. Interfaces between a thin (100 nm) layer of the block copolymer and a thick (100 μm) layer of the acrylic copolymer were prepared at room temperature and subsequently annealed for 7 h at different temperatures. After the annealing step, the interface was quenched to room temperature and tested, a strategy that provides the advantage of keeping constant the mechanical properties of the materials on both sides of the interface so that any major difference in adhesive behavior can only be attributed to a change in the interfacial structure. For annealing temperatures below the crystalline to liquid crystalline transition temperature (86 °C), the adhesion energy remained very low and failure occurred by interfacial crack propagation. However when the interface was annealed above that temperature, a much higher adhesion energy was observed at room temperature because of the formation of a fibrillar structure upon debonding. The results indicate that the crystalline order at low temperature is very stable presumably because of the strong interactions between the sulfone groups in the side chains. However, when these interactions weaken and the side chains become liquid crystalline, the surface reconstruction mechanism cannot be prevented and strong interactions formed between the polar parts of the copolymer and the acrylic acid. These strong interactions remain during the cooling step, and a mechanism of surface reconstruction is proposed. [ABSTRACT FROM AUTHOR]

The interactions between BF 4−ions (from the ionic liquid BMIM +BF 4−) and the surfaces of silver nanoparticles caused the Ag surfaces to be partially positively charged, resulting in increased activity in silver−olefin complexation. The surface positive charge was confirmed by the increase in binding energy of the d 5/2orbital of the silver nanoparticles from 368.26 to 369.12 eV as the silver content increased. The surface positive charge and consequent enhancement in olefin complexation ability were exploited through the use of silver nanoparticles as a new type of olefin carrier for facilitated transport. As a result, membranes containing BMIM +BF 4−/Ag nanoparticles demonstrated a mixed-gas selectivity of 17 for a 50/50 (vol %) propylene/propane mixture and showed stable performance for 100 h. [ABSTRACT FROM AUTHOR]

Summary  We observed that a new anionic triarylamine copolymer, which is easily accessable by radical polymerization can be used for the preparation of thin semiconducting organic films in two extremely different ways: One is the LBL assembly from solution with a cationic polyelectrolyte as counter system; the other is direct vacuum deposition, whereby the polymer degrades to oligomers, but keeps the functional groups intact as proved by UV/Vis, NMR spectroscopy and cyclic voltammetry. The fabricated films are used in light emitting devices as hole transporting layers showing excellent properties. External EL quantum efficiency (ηext) and luminous efficiency-current density (J) characteristics of PLED device were studied. [ABSTRACT FROM AUTHOR]

We have investigated the low-temperature cure process to realize nanoporous organosilicate thin films at temperature below 150°C by adding a small amount of photoacid generator (PAG) followed by UV irradiation. The Gemini surfactant, which decomposes in the temperature range from 170 to 420°C, was used as a pore-generating material (porogen) for organosilicate matrix. The UV pretreatment in the presence of PAG lowers the condensation temperature of poly(methyl silsesquioxane) matrix and leads to the fast matrix vitrification enabling the addition of increased amount of porogens. Because the full vitrification of the matrix (150°C) by UV pretreatment in the presence of PAG below the decomposition temperature of porogens (170°C) prevents the pore collapse, the porosity up to 35.5% was achieved with an average pore size of 3.4 nm, as measured from X-ray reflectivity as well as ellipsometric porosimetry. It is shown that both dielectric constant and refractive index continue to decrease to 2.0 and 1.26, respectively. The present experimental system demonstrates that porogens with low degradation temperature can be successfully incorporated to realize nanoporous films without pore collapse. Consequently, this process can widen the choice of porogens to prepare nanoporous films. [ABSTRACT FROM AUTHOR]

A nearly symmetric polystyrene-block-polyisoprene diblock copolymer dissolved at a concentration of 40% in styrene-selective solvents exhibited a cylinder-to-disorder transition upon heating. The solvents used were diethyl phthalate (DEP) and 75:25 and 50:50 mixtures of DEP with di-n-butyl phthalate (DBP). In DEP, the most styrene-selective of the three solvents, rheological measurements indicated a distinct plateau in the temperature-dependent elastic modulus across the 8 °C interval above the order−disorder transition temperature, TODT 116 °C. Previous small-angle neutron scattering measurements in this regime indicated the equilibrium phase to be a liquidlike solution of approximately spherical micelles. An isothermal frequency sweep in this regime indicated a very long relaxation time. Annealing eventually led to the recovery of liquidlike rheological response, over a time scale of hours. Qualitatively similar phenomena were also observed in 75:25 DEP/DBP and 50:50 DEP/DBP solutions, except the fact that the temperature window of the transient response is narrow and the time scale for the recovery diminishes significantly. Neither small-angle X-ray scattering nor static birefringence gave any clear signature of the transient structure. The structure that leads to the transient rheological response is attributed to micellar congestion due to the slow relaxation of anisotropic micelles into an equilibrium distribution of micelles. Possible origins of the remarkable solvent selectivity dependence are also discussed. [ABSTRACT FROM AUTHOR]

Two different kinds of organic polyelectrolyte (PE)/inorganic silicate nanolaminates carrying dissimilar interfacial adhesion between the organic and the inorganic layers were prepared using the layer-by-layer self-assembly. To investigate the mechanical behavior of the prepared hybrid films, apparent modulus (E′), hardness (H), and crack length were measured by depth-sensing nanoindentation as well as a microVickers experiment. The fracture toughness of the hybrid films was then calculated based on the measured mechanical values. In the case of forming strong interfacial adhesion between the organic and the inorganic layers (A series), the fracture toughness and the crack resistance of hybrid multilayer films were significantly improved as a result of the redistribution of stress concentration and the dissipation of fracture energy by the plasticity of organic PE layers. On the other hand, samples with relatively low interfacial adhesion between the organic and the inorganic layers (T series) had little effect on the improvement of fracture toughness of the hybrid films. [ABSTRACT FROM AUTHOR]

A new method is introduced to build organic/organic multilayer films composed of cationic poly(allylamine hydrochloride) (PAH) and negatively-charged poly(sodium 4-styrenesulfonate) (PSS) using the spinning process. The adsorption process is governed by both the viscous force induced by fast solvent elimination and the electrostatic interaction between oppositely-charged species. On the other hand, the centrifugal and air shear forces applied by the spinning process enhance significantly the desorption of weakly-bound polyelectrolyte chains and also induce the planarization of the adsorbed polyelectrolyte layer. The surface of the multilayer films prepared with the spinning process is quite homogeneous and smooth. Also, a new approach to create multilayer ultrathin films with well-defined micropatterns in short process time is introduced. To achieve such micropatterns with high line resolution in organic multilayer films, microfluidic channels were combined with the convective self-assembly process employing both hydrogen bonding and electrostatic intermolecular interactions. As a next step, we extended the spin SA to the fabrication of multilayer micropatterns with vertical heterostructure. [ABSTRACT FROM AUTHOR]

Although sol–gel IZO thin films are entirely porous, there are local dense regions at the surface and interface. From the relationship between the refractive index and thickness, we found that densified regions are maximized to the level of sputter thin films’ density when the thickness is reduced. TFT devices with one-layer and four-layer IZO channels with the same thickness of 200 Å were compared. The four-layer channel showed a field-effect mobility of 9.06 cm2 V−1 s−1. This result shows an improvement of five times compared to the 1.95 cm2 V−1 s−1 of the one-layer channel, thus validating the effect of densification. [ABSTRACT FROM AUTHOR]

We demonstrate the improvement in the efficiency of planar heterojunction perovskite solar cells by employing cadmium selenide tetrapods (CdSe TPs) as an electron extraction layer. The insertion of the CdSe TP layer between the titanium oxide (TiO2) and perovskite film facilitates electron transfer at the TiO2/perovskite interface, as indicated by the significantly quenched steady-state photoluminescence of the perovskite film. Furthermore, we observed a conductivity enhancement of the perovskite film by introducing the CdSe TP layer. The combination of both effects induced by the TPs leads to enhancement in the carrier extraction as well as decreased recombination losses in the perovskite solar cells. As a result, an efficiency of 13.5% (1 sun condition) is achieved in the perovskite solar cells that incorporate the CdSe TP layer, which is 10% higher than that of the device without the CdSe TP layer. [ABSTRACT FROM AUTHOR]

We report on a sequential ligand exchange and elimination process for the fast and easy surface modification of CdSe quantum dots (QDs) in order to improve the electronic interaction between poly(3-hexylthiophene) (P3HT) and CdSe QDs in P3HT:CdSe hybrid solar cells. We systematically investigated the influence of surface treatment on the insulating ligand shell of CdSe QDs using 1H-NMR analysis, and correlated their influence on the photovoltaic properties of P3HT:CdSe hybrid solar cells. A decrease in the average thickness of the ligand shells directly improved carrier transport properties. Moreover, the presence of remnant 1-hexylamine ligands provided efficient surface trap passivation. As a result, overall solar cell performance (especially fill factor and power conversion efficiency) was enhanced and the recombination mechanism was dominated by monomolecular recombination due to enhanced carrier collection length (lC0). [ABSTRACT FROM AUTHOR]

We demonstrate deep blue light-emitting diodes based on chemically synthesized Cd1[?]xZnxS@ZnS quantum dots (QDs). Composite films of poly-(N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine) (poly-TPD) and 4,4',N,N'-diphenylcarbazole (CBP) are employed for facilitated hole injection into Cd1[?]xZnxS@ZnS QDs and uniform QD deposition. The fabricated devices possess moderate turn-on voltage (6 V) and external quantum efficiency (0.1-0.3%), and exhibit color-saturated blue emission with a narrow spectral bandwidth of full width at half maximum <25 nm (Commission Internationale de l'Eclairage (CIE) coordinates of (0.169, 0.024) and (0.156, 0.028) for devices with electroluminescence (EL) lmax at 434 and 454 nm, respectively). Most of the emission originates from the Cd1[?]xZnxS@ZnS QD layers (99% of the total EL emission). [ABSTRACT FROM AUTHOR]

A new approach to realize multilayer micropatterns with vertical heterostructure is introduced. In this approach, well-defined micropatterns of poly(4-vinylpryridine) (PVP) and poly(acrylic acid) (PAA) multilayer are prepared in short process time by using microfluidic channels combined with the convective self-assembly process (i.e., the self-assembling process in the presence of external flow). The resulting patterns were then used as templates for further spin-coating process of poly(diallyldimethyl ammonium chloride) (PDAC) and poly(sodium 4-styrenesulfonate) (PSS). The micropatterns with sharp edge boundaries and small ridges at the edges were obtained for alternating (PVP/PAA) 5 /(PDAC/PSS) 40 multilayers. [ABSTRACT FROM AUTHOR]

We introduce a novel and versatile approach for preparing self-assembled nanoporous multilayered films with tunable optical properties. Protonated polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) and anionic polystyrene-block-poly(acrylic acid) (PS-b-PAA) block copolymer micelles (BCM) were used as building blocks for the layer-by-layer assembly of BCM multilayer films. BCM film growth is governed by electrostatic and hydrogen-bonding interactions between the opposite BCMs. Both film porosity and film thickness are dependent upon the charge density of the micelles, with the porosity of the film controlled by the solution pH and the molecular weight (Mw) of the constituents. PS7K-b-P4VP28K/PS2K-b-PAA8K films prepared at pH 4 (for PSTK-b-P4VP28K) and pH 6 (for PS2K-b-PAA8K) are highly nanoporous and antireflective. In contrast, PS7K-b-P4VP28K/PS2K-b-PAA8K films assembled at pH 4/4 show a relatively dense surface morphology due to the decreased charge density of PS2K-b-PAAsK. Films formed from BCMs with increased PS block and decreased hydrophilic block (P4VP or PAA) size (e.g., PS36K-b-P4VP12K/PS16K-b-PAA4K at pH 4/4) were also nanoporous. This is attributed to a decrease in interdigitation between the adjacent corona shells of the low Mw BCMs, thus creating more void space between the micelles. Multilayer films with antireflective and photochromic properties were obtained by incorporating a water-insoluble photochromic dye (spiropyran) into the hydrophobic PS core of the BCMs assembled in the films. The optical properties of these films can be modulated by UV irradiation to selectively and reversibly control the transmission of light. Light transmission of higher than 99% was observed with accompanying photochromism in the (PS7K-b-P4VP28K/PS2K-b-PAA8K) multilayer films assembled at pH 4/6. Our approach highlights the potential to incorporate a range of materials, ranging from conventional hydrophilic materials with specific interactions to hydrophobic compounds, into the assembled BCMs to yield multifunctional nanoporous films. [ABSTRACT FROM AUTHOR]

The article presents a unique one-step vapor-phase process, termed sulfur chemical vapor deposition, to generate highly stable, ultrahigh refractive index polymers directly from elemental sulfur. It mentions the high refractive index polymers (HRIPs) have emerged as an important class of materials for use in a variety of optoelectronic devices including image sensors, lithography, and light-emitting diodes.