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Analysis of nanostructures is of increasing importance with advances of nanotechnology. Embedded nanostructures in thin films in particular are of recent interest. Grazing incident small angle x-ray scattering (GISAXS) has been recognized to be a powerful method to probe such embedded nanostructures; however, quantitative analysis of scattering pattern is not always trivial due to complex refraction and reflection at surface and interfaces. We prepared nanocellular thin films using block copolymer template with carbon dioxide (CO2); CO2 “bubbles” were formed in the CO2-philic block domains. Such nanocellular structures were analyzed by GISAXS and simulated using distorted wave Born approximation (DWBA). Unlike traditional transmission x-ray scattering, GISAXS requires a careful choice of incident angle to analyze the form factor of scatters embedded in a thin film. Nevertheless, the GISAXS measurements under optimized geometry with quantitative calculations using DWBA revealed that the nanocells are spherical and aligned in a single layer of hexagonal lattice and are surrounded by CO2-philic block domains. [ABSTRACT FROM AUTHOR]

Abstract: We found a drastic change in orientation of cylindrical microdomains from perpendicular to parallel with respect to the film surface by thermal annealing for a liquid crystalline diblock copolymer, PEO122‐PMA(Az)50, consisting of poly(ethylene oxide) (PEO) and poly(methacrylate) with the side chain of a liquid crystalline azobenzene moiety. Non‐contact mode AFM (atomic force microscopy) is used to observe the orientation of cylinders on the surface of the film specimen. Perpendicular orientation of the PEO cylinders for the as‐spin‐coat specimen is found to change drastically to the parallel orientation as a function of the thermal annealing time at 140 °C. It is interesting to find inclined cylinders in the course of the transition. Grazing‐incidence small‐angle X‐ray scattering is also conducted to analyze the cylinder orientation in the interior of the specimen. As a result, the parallel orientation of the PEO cylinders is found even for the case when the inclined cylinders are detected by AFM on the surface of the film specimen. [ABSTRACT FROM AUTHOR]

Method of evaluation of grain size of hexagonally-packed cylindrical microdomains is presented by taking as an example the data from the polystyrene-block-polyethylenebutylene-block-polystyrene (SEBS) triblock copolymer film, where the polystyrene cylinders are embedded in the polyethylenebutylene matrix with being oriented perpendicular to the surface of the film. For this purpose, the two-dimensional small-angle X-ray scattering was measured by illuminating X-ray beam from the side of the film. The procedure is similar to the method how to evaluate the crystallite size of polymer, using the peak width of crystalline reflection in the wide-angle X-ray diffraction (WAXD) measurement. While single crystal is used as the standard sample for the case of WAXD because it can be postulated that the crystallite size is infinity in the single crystal, we propose here to use collagen as a standard sample for the SAXS measurement, since collagen forms very regular stacking of texture with 65.3 nm repeating period and the number of the stacking texture is infinitely large. It was confirmed that the grain size evaluated by the SAXS method was in sufficient accord with the result of the transmission electron microscopic observation. [ABSTRACT FROM AUTHOR]

Two-dimensional molecular aggregation states of polyalkylsiloxane ultrathin films on silicon wafer substrates surface were investigated by various techniques. The in-plane grazing incidence X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, and scanning force microscopy revealed that the alkyl chains in the octadecyltrimethoxysilane (OTMS) ultrathin films prepared by the CVA method (OTMS-CVA) are in an amorphous state at room temperature. On the other hand, octadecyltrichlorosilane (OTS) ultrathin films prepared by the solution chemisorption method and water-cast method are in a hexagonal crystalline state. According to lateral force microscopic measurements, the transition temperature from the hexagonal crystalline phase to the amorphous phase was found to be ca 333 K for the OTS ultrathin film prepared by the chemisorption method. However, the phase transition was not clearly observed in the OTMS-CVA ultrathin film. These results indicated that organosilane compounds in the ultrathin film prepared by the CVA method were immobilized on the silicon wafer substrate surface in an amorphous state, which was quite different from the hexagonal crystalline state obtained by the solution chemisorption and water-cast methods. [ABSTRACT FROM AUTHOR]

Molecular aggregation structure of poly(fluoroalkyl acrylate) [PFA-Cy, where y is the fluoromethylene number of the fluoroalkyl (Rf) groups] thin films was characterized by grazing-incidence X-ray diffraction (GIXD). In-plane diffractions corresponding to the hexagonal packing of the Rf groups were measured for PFA-Cy with y ≥ 8 in the surface and bulk regions. This result indicated that the Rf groups were oriented almost perpendicular to the film surface. [ABSTRACT FROM AUTHOR]

We have investigated lamellar stacking structure of melt-crystallized and annealed high-density polyethylene (HDPE) thin films, with a thickness of ca 400 nm prepared on silicon wafers, using synchrotron grazing-incidence small-angle and wide-angle X-ray scattering (GISWAXS) measurements at the BL40B2 beamline in SPring-8. In-situ measurements of GISWAXS were carried out for the films in a stepwise annealing process under vacuum. Scattering peaks relating to the long period, the average distance between stacked crystalline lamellae, were measured only in the in-plane direction near the Yoneda peak of the grazing-incidence small-angle X-ray scattering patterns. On the other hand, the orthorhombic (110) and (200) reflections of oriented HDPE crystals were measured in the out-of-plane direction of the grazing-incidence wide-angle X-ray scattering patterns. It was revealed that crystalline lamellae were stacked in a parallel direction to the film surface and the long period increased from ca 25 nm to ca 32 nm in a stepwise annealing process. Within a lamella, molecular chains were found to be packed regularly and the chain axis (the c axis) was relatively oriented parallel to the film surface. [ABSTRACT FROM AUTHOR]

Abstract: Oriented films of cellulose prepared from algal cellulose were hydrothermally treated to convert them into highly crystalline cellulose Iβ. The lateral thermal expansion behavior of the prepared cellulose Iβ films was investigated using X-ray diffraction at temperatures from 20 to 300°C. Cellulose Iβ was transformed into the high-temperature phase when the temperature was above 230°C, allowing the lateral thermal expansion coefficient of cellulose Iβ and its high-temperature phase to be measured. For cellulose Iβ, the thermal expansion coefficients (TECs) of the a- and b-axes were αa =9.8×10−5 °C−1 and αb =1.2×10−5 °C−1, respectively. This anisotropic thermal expansion behavior in the lateral direction is ascribed to the crystal structure and to the hydrogen-bonding system of cellulose Iβ. For the high-temperature phase, the anisotropy was more conspicuous, and the TECs of the a- and b-axes were αa =19.8×10−5 °C−1 and αb =−1.6×10−5 °C−1, respectively. Synchrotron X-ray fiber diffraction diagrams of the high-temperature phase were also recorded at 250°C. The cellulose high-temperature phase is composed of a two-chain monoclinic unit cell, a =0.819nm, b =0.818nm, c (fiber repeat)=1.037nm, and γ =96.4°, with space group= P21. The volume of this cell is 4.6% larger than that of cellulose Iβ at 30°C. [Copyright &y& Elsevier]