The emerging ferroelectric nematic (N F ) liquid crystal is a novel 3D-ordered liquid exhibiting macroscopic electric polarization. The combination of the ultrahigh dielectric constant, strong nonlinear optical signal, and high sensitivity to the electric field makes N F materials promising for the development of advanced liquid crystal electroopic devices. Previously, all studies focused on the rod-shaped small molecules with limited length (l) range and dipole moment (μ) values. Here, through the precision synthesis, we extend the aromatic rod-shaped mesogen to oligomer/polymer (repeat unit up to 12 with monodisperse molecular-weight dispersion) and increase the μ value over 30 Debye (D). The N F phase has a widespread existence far beyond our expectation and could be observed in all the oligomer/polymer length range. Notably, the N F phase experiences a nontrivial evolution pathway with the traditional apolar nematic phase completely suppressed, i.e., the N F phase nucleates directly from the isotropic liquid phase. The discovery of thte ferroelectric packing of oligomer/polymer rods not only offers the concept of extending the N F state to oligomers/polymers but also provides some previously overlooked insights in oxybenzoate-based liquid crystal polymer materials.

Polymers with low dielectric permittivity and dielctric loss are essential for microelectrics and wireless communication industries. Perfluorocyclobutyl (PFCB) aryl ether group is proved to afford polymer materials with high fluorine...

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The emerging ferroelectric nematic liquid crystals have been attracting broader interests in new liquid crystal physics and their unique material properties. One big challenge for the ferroelectric nematic researches is...

Molecular solar thermal fuels (MOSTs), especially azobenzene-based MOSTs (Azo-MOSTs), have been considered as ideal energy-storage and conversion systems in outer or confined space because of their “closed loop” properties. However, there are two main obstacles existing in practical applications of Azo-MOSTs: the solvent-assistant charging process and the high molar extinction coefficient of chromophores, which are both closely related to the π–π stacking. Here, we report one efficient strategy to improve the energy density by introducing a supramolecular “cation−π” interaction into one phase-changeable Azo-MOST system. The energy density is increased by 24.7% (from 164.3 to 204.9 J/g) in Azo-MOST with a small loading amount of cation (2.0 mol %). Upon light triggering, the cation−π-enhanced Azo-MOST demonstrates one gravimetric energy density of about 56.9 W h/kg and a temperature increase of 8 °C in ambient conditions. Then the enhanced mechanism is revealed in both molecular and crystalline scales. This work demonstrates the huge potential of supramolecular interaction in the development of Azo-MOST systems, which could not only provide a universal method for enhancing the energy density of solar energy storage but also balance the conflicts between molecular design and the condensed state for phase-changeable materials.

Aiming at fabricating the polyimide (PI) films with low permittivity and excellent comprehensive properties, 2,2′‐bis‐(trifluoromethyl)‐4,4′‐diaminobiphenyl was incorporated into the polyimide backbone composed of 3,3′,4,4′‐biphenyltetracarboxylic dianhydride and p‐phenylenediamine. The introduction of trifluoromethyl (CF3) groups led to a substantial reduction of the PI's permittivity (3.42–2.96). Meanwhile, as‐prepared co‐PI films showed excellent mechanical performance (217.13–238.20 MPa for strength and 3.49–4.90 GPa for modulus), as well as good thermal stability (high glass transition temperature over 354 °C, whereas low thermal expansion coefficient below 10 ppm/K). Structure–property relationship of the PI samples was further established through molecular simulations (MS), which suggested the crucial effects of polarizability per unit volume (α/Vvdw) and free volume on PI permittivity. The computational results were highly consistent with the experimental findings, meaning that MS technique is of guiding importance in copolymer design. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47989.

Recently, we have demonstrated a general molecular design for emerging ferroelectric nematic liquid crystals by introducing large dipole moment and local bulkiness into rod-shaped mesogenic molecules. The giant dielectricity and strong nonlinear optic properties in the ferroelectric nematic liquid crystal materials could bring the vast technological potential for flexible supercapacitors, electro-optic devices, and nonlinear optical devices. Here, we extend the polar liquid crystal material from small molecules to polymer systems by elaborately manipulating the interplay between the side-chain joint position and dipole–dipole interaction. For this purpose, we developed three series of side-chain liquid crystalline polymers. We clarify that the polymers with side-jointed mesogens exhibit a polar nematic liquid crystalline phase with strong polarity confirmed by second harmonic generation, while the polymers with end-jointed mesogens self-assemble into a smectic A phase with no polarity. The magnitude of dipole moment was also critical for producing the macroscopic polarity in these side-chain liquid crystalline polymers.

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