Effect of Substrate Surfaces for Crystal Growth of a Photochromic Diarylethene by Sublimation

Abstract

The state of the substrate surface is one of the key factors in varying morphologies of crystals produced by the sublimation method of some organic compounds. In this work, we succeeded in separately preparing different morphologies of rodlike crystals of 1,2-bis­(2,5-dimethyl-3-thienyl)­perfluorocyclopentene (1a), which are classified into the hollow crystal and the feather-like crystal, by sublimation to glass substrates with the hydrophilic and hydrophobic surfaces, respectively. To clarify the crystal growth process on each surface of the glass substrate, we investigated miller indices of crystal faces attached to the substrate surface in the early stage of sublimation and crystal growth directions of these rodlike crystals from these crystal faces by X-ray diffraction measurements and polarizing microscopic observation. As a result, it was revealed that the heterojunction between the crystal faces produced in the early and following stages of sublimation leads to two different crystal morphologies. Moreover, it was confirmed that the heterojunctions occur in a specific orientation between these crystal faces because the lattice points in these crystal faces are in good agreement. Finally, we have demonstrated photomechanical behaviors of the hollow and feather-like crystals.

Fabrication of Hyperbranched Photomechanical Crystals Composed of a Photochromic Diarylethene

“…The crystal growth rate in the directions along the [100] direction is faster than that in the directions along the [111] direction as is evident from SEM images of the tip of each of the branched hollow crystals. In other words, the direction parallel to the straight line connecting the two vertexes with acute angles on the cross‐section of the hollow crystals is identified with the crystal growth direction of the feather‐like crystals, which undergoes the crystal growth process at the relative fast rate according to the crystal growth process of the feather‐like crystals observed by the digital microscope, according to our previous work [34] …”

“…In other words, the direction parallel to the straight line connecting the two vertexes with acute angles on the cross-section of the hollow crystals is identified with the crystal growth direction of the feather-like crystals, which undergoes the crystal growth process at the relative fast rate according to the crystal growth process of the feather-like crystals observed by the digital microscope, according to our previous work. [34]…”

“…When powder crystals of 1 a are heated at 100 °C under the control of the relative humidity, the rodlike crystals having the different crystal morphology, the hollow and feather-like crystals, are produced densely on the hydrophilic and hydrophobic substrate surfaces, respectively. [34] The hollow crystals bend toward the light source, whereas the feather-like crystals bend against the light source under the irradiation with UV light. Besides, X-ray diffraction (XRD) patterns for polycrystalline thin films of 1 a formed in the sublimation process show that the crystal faces of the (100) and 01 � 1 ð Þ planes are generated on the hydrophilic and hydrophobic substrate surfaces, respectively.…”

“…In our previous work, we have investigated the crystal growth of 1,2‐bis(2,5‐dimethyl‐3‐thienyl)perfluorocyclopentene, 1 a (Figure 1) on the glass substrate surface in the sublimation process. When powder crystals of 1 a are heated at 100 °C under the control of the relative humidity, the rodlike crystals having the different crystal morphology, the hollow and feather‐like crystals, are produced densely on the hydrophilic and hydrophobic substrate surfaces, respectively [34] . The hollow crystals bend toward the light source, whereas the feather‐like crystals bend against the light source under the irradiation with UV light.…”

Controllable Fabrication of Organic Cocrystals with Interior Hollow Structure Based on Donor-Acceptor Charge Transfer Molecules

“…The self-assembly method offers an effective and fast way to make molecular crystals with different shapes and sizes from solutions. Moreover, it has been reported that complicated crystal topologies, such as unique tubular and hollow structures, could be obtained during crystal growth by regulating intermolecular interactions such as π-π interactions [23][24][25][26].…”