Structural characterization of the Fddd phase in a diblock copolymer thin film by electron microtomography

A 3-dimensional Fddd network structure of a polystyrene-block-polyisoprene (PS-b-PI) diblock copolymer (M(n) = 31 500, f(PI) = 0.645) was observed for the first time in real space by transmission electron microtomography (TEMT). In a 650 nm thick film of the PS-b-PI thin film on a silicon wafer, the Fddd phase was developed after annealing at 215 degrees C for 24 h. The single network structure consists of the connected tripodal units of minor PS block domains. The {111}(Fddd) plane, the densest plane of the minor PS phase, was found to orient parallel to the film plane. The transitional structure from the wetting layer at the free surface to the internal {111}(Fddd) plane via a perforated layer structure was also observed.X111313sciescopu

Solution structures of RseA and its complex with RseB

Conformational changes of RseA and RseB were observed by circular dichroism and small-angle X-ray scattering upon the formation of their complex

Chemically Denatured Structures of Porcine Pepsin using Small-Angle X-ray Scattering

Porcine pepsin is a gastric aspartic proteinase that reportedly plays a pivotal role in the digestive process of many vertebrates. We have investigated the three-dimensional (3D) structure and conformational transition of porcine pepsin in solution over a wide range of denaturant urea concentrations (0–10 M) using Raman spectroscopy and small-angle X-ray scattering. Furthermore, 3D GASBOR ab initio structural models, which provide an adequate conformational description of pepsin under varying denatured conditions, were successfully constructed. It was shown that pepsin molecules retain native conformation at 0–5 M urea, undergo partial denaturation at 6 M urea, and display a strongly unfolded conformation at 7–10 M urea. According to the resulting GASBOR solution models, we identified an intermediate pepsin conformation that was dominant during the early stage of denaturation. We believe that the structural evidence presented here provides useful insights into the relationship between enzymatic activity and conformation of porcine pepsin at different states of denaturation

Comprehensive synchrotron grazing-incidence X-ray scattering analysis of nanostructures in porous polymethylsilsesquioxane dielectric thin films

A complete grazing-incidence X-ray scattering (GIXS) formula has been derived for nanopores buried in a polymer dielectric thin film supported by a substrate. Using the full power of the scattering formula, GIXS data from nanoporous polymethylsilsesquioxane dielectric thin films, a model nanoporous system, have successfully been analysed. The nanopores were found to be spherical and to have a certain degree of size distribution but were randomly dispersed in the film. In the film, GIXS was confirmed to arise predominantly via the first scattering process in which the incident X-ray beam scatters without reflection; the other scattering processes and their contributions were significantly dependent on the grazing angle. This study also confirmed that GIXS scattering can be analysed using only independent scattering terms, but this simple approach can only provide structural parameters. The cross terms were found to make a relatively small contribution to the intensity of the overall scattering but were required for the complete characterization of the measured two-dimensional scattering data, in particular the extracted out-of-plane scattering data, and their inclusion in the analysis enabled film properties such as film thickness, critical angle (i.e. electron density), refractive index and the absorption term to be determined.open111818sciescopu

Liquid crystal alignment in advanced flat-panel liquid crystal displays

The alignment of liquid crystal (LC) molecules at display boundaries is the major factor determining the electro-optical performance of liquid crystal display (LCD) devices. Most LC alignments are induced by interactions with the alignment material layer, whose surface is in physical contact with the LC molecules in LCD devices. Despite its importance, the mechanism governing the alignment of LC molecules on alignment layers is still not well understood. This review discusses the major factors controlling LC alignment and the polymer materials used.1167sciescopu

Preparation of Nanoporous Poly(3-hexylthiophene) films based on a Template System of Block Copolymers via Ionic Interaction

A series of well-defined aniline-chain-end-functionalized regioregular poly(3-hexylthiophene)s (P3HT-NH2) and sulfo-chain-end-functionalized polystyrene (PS-SO3H) have been prepared based on quasi-living Grignard metathesis and living anionic polymerization, respectively. Block copolymers via ionic interaction. (P3HT-NH3+)-b-(PS-SO3(-))s, were successfully synthesized, simply by blending P3HT-NH2 with PS-SO3H in toluene. The thermal and optical properties of the block copolymers were investigated by differential scanning calorimetry (DSC) and ultraviolet visible (UV-vis) spectroscopy. The self-assembly behavior of the (P3HT-NH3+)-b-(PS-SO3-) thin film was observed by atomic force microscopy (AFM) and transmission electron microscopy (TEM). In addition, grazing incidence X-ray scattering (GIXS) analysis found the microphase separation of P3HT-NH3+ and PS-SO3- domains as well as the packing behavior of P3HT-NH3+ segments in block copolymer thin films. By exploiting the pH-sensitive ionic interaction, the PS-SO3- domains were selectively etched with ethyl acetate/triethylamine, cleaving the ionic interaction between P3HT-NH3+ and PS-SO3- segments. to obtain the target nanoporous P3HT-NH2, films. The porosity of the films was confirmed by AFM, scanning electron microscopy (SEM) and GIXS analyses.X1153sciescopu

Morphology-Driven High-Performance Polymeric Photodetector

The influence of polymer/fullerene morphology on photodetector performance is reported. Various morphologies of spin-coated films are generated by different blending ratio. Morphological study combined with measurement of charge carrier mobility reveals that blend films with an excess content of crystalline fullerene have a phase-separated morphology, resulting in enhanced charge carrier mobility. Under this phase separated morphology, photovoltaic performance is enhanced because of the generation of percolating pathways for charge carriers. Interestingly, however, a homogeneous morphology is found to be more beneficial for photodetector application than this phase separated morphology. An optimized device displayed 3 dB bandwidth up to I kHz and detectivities up to D = 1.1 X 10(10) cm Hz(1/2) W-1. These results emphasize the importance of developing an independent strategy for designing high performance photodetectors separately from solar cell devices both in terms of materials and device geometry. Possible relations between morphology and various figures of merit of photodetectors are discussed.X111312sciescopu

A Lattice-Strained Organic Single-Crystal Nanowire Array Fabricated via Solution-Phase Nanograting-Assisted Pattern Transfer for Use in High-Mobility Organic Field-Effect Transistors

A 50 nm-wide 6,13-bis(triisopropylsilylethynyl) pentacene nanowire array is fabricated on a centimeter-sized substrate via a facile nanograting-assisted pattern-transfer method. Nanowire growth under a nanoconfined space adopts a lattice-strained packing motif of the NWs for strong intermolecular electronic coupling, and thus a nanowire-based organic field-effect transistor shows high field-effect mobility up to 9.71 cm(2) V-1 s(-1).111310sciescopu

Molecular Layer-by-Layer Self-Assembly and Mercury Sensing Characteristics of Novel Brush Polymers Bearing Thymine Moieties

Two new brush polyoxyethylenes bearing thymine moieties at the bristle ends have been synthesized as model polymers in which the chemical loading of the thymine functional group into the polymer is maximized: poly(oxy(11-thyminoacetyloxyundecylthiomethypethylene) (PECH(S)-T) and poly(oxy(11-thyminoacetyloxyundecylsulfonylmethyl)ethylene) (PECEI(SO2)-T). These brush polymers are thermally stable up to around 225 degrees C, and their glass transitions occur in the range 23-27 degrees C, but they have significantly different proper:ies despite the similarity of their chemical structures. In particular, PECH(SO2)-T films exhibit better performance in sensing mercury ions than PECH(S)-T films. These differences were found to originate in the differences between their morphological structures. The PECH(SO2)-T film has a multibilayer structure without interdigitation, in which the layers stack along the out-of-plane of the film and provide a thymine-rich surface. In contrast, the PECH(S)-T film is amorphous with a relatively low population of thymine moieties at the surface. This study demonstrated that a thymine-rich surface is required for recyclable thyrnine-based polymers to provide highly improved sensitivity and selectivity as well as full reversibility in the sensing of mercury ions. A thymine-rich surface can be achieved with a brush polymer hnring thymine moieties that can self-assemble into a multi-bilayer structure. Because of the thymine-rich surface, the PECH(SO2)-T thin films even in only 6 nm thickness demonstrate the detection of mercury ions in aqueous solutions with a detection limit of 10(-6) M.X111414sciescopu