![]() ![]() Self-assembly of organic or inorganic compounds, of either small-molecules or polymers, has been interesting and intriguing, yet complex issues, in soft matters either synthetic or natural. Crystallization of atoms or molecular compounds into ordered states has been a complex yet fascinating phenomenon that has attracted extensive scientific studies from classical to modern times, to cite just a few recent examples 1, 2, 3. The crystallization process may occur in sequential steps to gradually increase the degree of order while in the meantime the hierarchical aggregation structures may diversify in patterns and vary significantly in increasingly higher-order morphologies. Similar content being viewed by othersĬooling of a matter in liquid state causes it to crystallize into either 2D or 3D ordered states. The detailed growth mechanisms of the novel fractal-branching assembly into circular- or grating-banded patterns are analyzed in this work. Crystal assembly of these three periodic morphologies was analyzed by utilizing atomic-force microscopy (AFM) and scanning electron microscopy (SEM) to reveal the mechanisms of formation of hierarchical structures of PA. ![]() A unique periodic fractal-branch pattern with contrasted birefringent bands exists at intermediate evaporation rate, and this unique grating architecture has never been found in other banded crystals. With increasing evaporation rate, the morphology of PA crystals systematically changes from circular-banded spherulites to highly ordered grating-banded patterns. Several compositions of the mixture of ethanol/water solutions and evaporation temperatures were also manipulated to investigate the kinetic effects on the morphology of PA crystals. Small-molecule phthalic acid (PA), confined in micrometer thin films, was crystallized in the presence of strongly interacting tannic acid (TA) to investigate crystal assembly and correlation between banded patterns and branching structures.
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