Photofabrication of surface relief grating (SRG) on very high-Tg and lower-Tg azobenzene functionalized polymers was investigated. Polymers with different degrees of functionalization were designed and synthesized to understand the chemical and physical intricacies involved at the molecular level in the photofabrication of SRG. The systematic study examined the influence of three important parameters: the degree of azo functionalization, the irradiating light intensity, and the initial film thickness. From the experimental results, we establish that the writing behavior of photofabricated SRG depends on the degree of azo functionalization. The effective critical intensity of the irradiating light was found to be independent of the degree of functionalization. Threshold behavior for the deformation process as a function of the degree of functionalization was established. The observed film thickness dependence of the SRG formation is discussed within the framework of existing fluid mechanics model. The thermal properties of the photofabricated SRG were also investigated.

The breaking of chiral symmetry can occur under nonequilibrated conditions. [1][2][3][4] Such a spontaneous induction of optical activity from achiral entities has attracted much attention in relation to the origin of chirality in nature. Representative examples can be seen in growth processes of large electrostatic assemblies of achiral chromophoric compounds such as cyanine dyes and porphyrin derivatives in aqueous media. [5] In these cases, the assemblies are considered to adopt helical architectures, where either the P or M form is selected only accidentally at the initial stage of the self-organization event and develops predominantly in the subsequent stage. Hence, handedness of emerging chirality is unpredictable. Ribó et al.[5c] have discovered, through studies on electrostatic Jaggregation of a 4-sulfonatophenylporphyrin in aqueous media, that the sense of such an optical activity can be selected by the spinning direction of vortex stirring initially applied to the solutions. Herein we report an interesting finding that spin-coated films of dendritic zinc porphyrin Jaggregates chiroptically memorize the spinning directions. The optical activities of the spin-coated films are thermally stable and preserved up to the melting temperatures of the Jaggregates. In contrast with the previous examples, [5] the Jaggregates are optically inactive in solution.Porphyrin J-aggregates have attracted attention because of their potential application as nonlinear optical materials. [6] Although several examples of porphyrin J-aggregates have been reported, they are formed mostly in aqueous media; [5b, c] however, there are few examples of J-aggregation in organic media [7] which occur because of rather weak p-stacking interactions. We found that zinc porphyrins bearing carboxylic acid (-CO 2 H) functionalities at the opposite meso positions undergo supramolecular polymerization by dimerization of the -CO 2 H groups to give J-aggregates in organic media. The J-aggregation takes great advantage of a multi-[*] Dr.

Lanthanum lithium titanate (LLTO) is one of the most promising electrolyte materials for all-solid-state lithium-ion batteries. Despite numerous studies, the detailed crystal structure is still open to conjecture because of the difficulty of identifying precisely the positions of Li atoms and the distribution of intrinsic cation vacancies. Here we use subangstrom resolution scanning transmission electron microscopy (STEM) imaging methods and spatially resolved electron energy loss spectroscopy (EELS) analysis to examine the local atomic structure of LLTO. Direct annular bright-field (ABF) observations show Li locations on O4 window positions in Li-poor phase La0.62Li0.16TiO3 and near to A-site positions in Li-rich phase La0.56Li0.33TiO3. Local clustering of A-site vacancies results in aggregation of Li atoms, enhanced octahedral tilting and distortion, formation of O vacancies, and partial Ti4+ reduction. The results suggest local LLTO structures depend on a balance between the distribution of A-site vacancies and the need to maintain interlayer charge neutrality. The associated local clustering of A-site vacancies and aggregation of Li atoms is expected to affect the Li-ion migration pathways, which change from two-dimensional in Li-poor LLTO to three-dimensional in Li-rich LLTO. This study demonstrates how a combination of advanced STEM and EELS analysis can provide critical insights into the atomic structure and crystal chemistry of solid ionic conductors.

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