Hierarchical superstructures from a star-shaped molecule consisting of a cyclic oligosiloxane with cyanobiphenyl moieties

Abstract

Unconventional star-shaped liquid crystals (abbreviated as SiLCs) were successfully synthesized by chemically connecting four cyanobiphenyl anisotropic mesogens to the periphery of a super-hydrophobic and ultra-flexible cyclic tetramethyltetrasiloxane ring with flexible hexyl chains. Based on the combined experimental techniques of differential scanning calorimetry (DSC), cross-polarized optical microscopy (POM), solid-state carbon-13 ((13)C) nuclear magnetic resonance (NMR) spectroscopy and one-dimensional (1D) wide-angle X-ray diffraction (WAXD), it was found that the SiLC molecule exhibited the monotropic phase transition from a LC phase to a crystalline phase. The crystalline phase was only detected during slow heating processes above its glass transition temperature, while a LC phase was formed both during cooling and during heating processes. The hierarchical superstructures were identified from the structure-sensitive 2D WAXD of the macroscopically oriented SiLC film and confirmed by selected area electron diffraction (SAED) of the SiLC single crystals. The molecular packing symmetry in the monoclinic unit cell was further investigated by computer simulations on the real and reciprocal spaces. Macroscopically oriented SiLC hierarchical superstructures on the different length scales may provide the targeted physical properties, which can allow us to apply SiLC molecules in the fields of electro-optical devices and nonlinear optics.

From Smart Denpols to Remote‐Controllable Actuators: Hierarchical Superstructures of Azobenzene‐Based Polynorbornenes

“…The onset transition at 137 °C does not show the supercooling effect. This implies that thermodynamic properties of the first‐order transition at 137 °C are close to those of the equilibrium state . A small transition observed at 131 °C corresponds to the phase transition to another LC phase (Figure S8, Supporting Information).…”

Solid‐State Light Emission Controlled by Tuning the Hierarchical Superstructure of Self‐Assembled Luminogens

“…As expected, the Iso state of AT 3 EMIS is confirmed at 185 °C by a complete dark state. The WAXD of AT 3 EMIS in the Iso state exhibits only amorphous halos at 2θ = 2.43° and 2θ = 18.8° . The low‐angle halo ( d = 3.64 nm) indicates the average periodicity of electron density fluctuations between the nanophase separated rigid chromophore, while the wide‐angle halo ( d = 0.47 nm) represents the average distance between the flexible dendrons.…”

Asymmetric Fullerene Nanosurfactant: Interface Engineering for Automatic Molecular Alignments

“…The asymmetric C 60 NS nanosurfactant designed and synthesized for the automatic molecular alignment could be used to fabricate electrically controllable birefringence modulators. The C 60 NS was synthesized by utilizing the Bingel reaction to covalently connect the rod‐like twin cyanobiphenyl derivative (BP 2 T) to the periphery of the C 60 nanoparticle with flexible alkyl chain spacers ( Figure ) . Detailed synthetic procedures and analytical data for C 60 NS and related intermediates, such as nuclear magnetic resonance (NMR), elemental mass (EM), ultraviolet‐visible (UV–vis), and Fourier transform infrared (FT IR) spectra, can be found in Figures S1–S7 in the Supporting Information.…”