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Information coding, recording, encryption, and decryption are of great importance in the field of anti‐counterfeiting, especially in the current AI information era. Herein, a paper‐like hydrogel composed of solely H‐bonded poly(vinyl alcohol) (PVA) and poly(n‐vinylcaprolactam) (PNVCL), namely VAPN, is developed for multiple ways of encryption and decryption based on chemical‐induced phase separation. It not only exhibits excellent ability of ink absorption and retention by the noncovalent H‐bonds and n−π* interactions and good mechanical strength but also maintains a negligible volume change during the phase separation that is crucial for the information fidelity. Given that the noncovalent interactions are the driving force to trigger the phase separation in the hydrogel, available chemical inks are numerous ranging from small molecules to polymers. Furthermore, together with thermally induced phase separation, the different dynamic processes of the association and dissociation between ink molecules and the hydrogel endow the latter with reversible information recording and self‐erasing, temporary or permanent, and customized encryption and decryption. [ABSTRACT FROM AUTHOR]

A series of non-symmetric dimers with the same chiral core, mandelic acid (MA), have been synthesised by varying the terminal group and the rigidity of the molecules, termed QBBMA-3F3BT, QBMA-3F3BT, QBMA-3F2BT, 3F3BMA-BBCN, 3F2BMA-BBCN and 3F1BMA-BBCN. Chemical structures and liquid crystal (LC) properties of the dimers were characterised by Fourier transform infrared spectroscopy, 1H NMR, polarised optical microscopy (POM), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and thermogravimetric analysis (TG). The six dimers displayed different optical activity (in THF). QBBMA-3F3BT and QBMA-3F3BT displayed enantiotropic chiral smectic A (SmA*) phase. QBMA-3F2BT displayed N phase. The Tm of QBMA-3F3BT is the highest among QBBMA-3F3BT, QBMA-3F3BT and QBMA-3F2BT, which indicated that molecular conformation played an important role on Tm besides molecular weight and molecular rigidity. 3F3BMA-BBCN and 3F2BMA-BBCN displayed chiral nematic (N*), which indicated that the mesogenic arm BBCN is beneficial to the formation of N* phase. The LC range of 3F2BMA-BBCN is wider, which may be due to that the similar length of the two LC arms is advantageous to the interaction between C≡N group and other molecules so as to stabilise the LC phase. [ABSTRACT FROM AUTHOR]

Six three-arm star-shaped liquid crystals (LCs) based on chenodeoxycholic acid (CDCA), termed as G-BH, G-YD, G-FD, G-DJ, G-DZ and G-BX, respectively, have been synthesised. CDCA was used as the chiral core and the nematic side arm, 6-(4-(ethylbenzoyloxy) phenoxy)-6-oxohexanoic acid, was chosen to be introduced into the two hydroxyl of CDCA to synthesise cholesteric LC (CDCA2EA) and different structures were introduced into the carboxyl group of CDCA to prepare the three-arm star-shaped LCs. Chemical structures and LC properties of the six three-arm LCs were characterised by FTIR, 1H-NMR, differential scanning calorimetry, thermogravimetric analysis, X-ray diffraction and polarised optical microscopy. G-BH and G-DJ displayed cholesteric phase with a long helical pitch; G-BX displayed nematic phase; and G-YD, G-FD and G-DZ displayed cholesteric phase on heating and on cooling. These results indicated that not only the chiral core CDCA but also the structures of the side arms played an important role in inducing the cholesteric phase of the CDCA-derived LCs. G-DZ displayed selective reflection, a wider ∆λ and red shift on cooling. [ABSTRACT FROM AUTHOR]

Four non-symmetric dimers containing mandelic acid as the chiral core have been synthesised, termed as QBMA-B, QBMA-BCN, QBMA-BBCN and QBBMA-BBCN, respectively. Chemical structures and liquid crystal (LC) properties of the dimers were characterised by FTIR, 1H-NMR, differential scanning calorimetry (DSC), thermogravimetric analysis (TG) and polarised optical microscopy (POM). The results indicated that the rigidity and conformation of the molecules of the dimers played important effects on their mesophase properties. QBMA-B did not display any mesophase, QBMA-BCN and QBMA-BBCN exhibited nematic (N) phases, while QBBMA-BBCN displayed cholesteric (ch) phase, which indicated that chiral mandelic acid could induce cholesteric phase, but some attention should be paid to the molecular conformation to obtain cholesteric phase. For the four dimers, melting temperature (Tm) increased first and then decreased, inferring that molecular conformation played a more important effect besides molecular weight and rigidity. [ABSTRACT FROM AUTHOR]

Covalent adaptable liquid crystal networks (CALCNs) are highly potential actuating materials due to their actuation properties and shape reprogrammability. Given the importance of network crosslinking state in a CALCN actuator, we sought an all‐in‐one strategy to probe and visualize its dynamic network while ensuring actuation and reprogramming. Here, tetraphenylethylene derivatives were incorporated into liquid crystal networks via the Diels–Alder (DA) reaction, acting simultaneously as reversible crosslinkers and aggregation‐induced emission (AIE) fluorescent probes. The thermally tunable fluorescence of the resulting network can correlate to and thus visualize the actuator's crosslinking status, actuation capability and temperature in real‐time and in situ, yielding an intriguing actuation limit‐alerting function. Furthermore, we verified unprecedented reprogrammability of the AIE‐type CALCNs through both associative and dissociative exchange mechanisms of DA chemistry. [ABSTRACT FROM AUTHOR]

Covalent adaptable liquid crystal networks (CALCNs) are highly potential actuating materials due to their actuation properties and shape reprogrammability. Given the importance of network crosslinking state in a CALCN actuator, we sought an all‐in‐one strategy to probe and visualize its dynamic network while ensuring actuation and reprogramming. Here, tetraphenylethylene derivatives were incorporated into liquid crystal networks via the Diels–Alder (DA) reaction, acting simultaneously as reversible crosslinkers and aggregation‐induced emission (AIE) fluorescent probes. The thermally tunable fluorescence of the resulting network can correlate to and thus visualize the actuator's crosslinking status, actuation capability and temperature in real‐time and in situ, yielding an intriguing actuation limit‐alerting function. Furthermore, we verified unprecedented reprogrammability of the AIE‐type CALCNs through both associative and dissociative exchange mechanisms of DA chemistry. [ABSTRACT FROM AUTHOR]

Two series of symmetric LC dimers with the same rigid group and different fluorine terminal group (F and F3C) have been synthesised by varying the length of flexible spacers, termed 1 F series (1 F-4, 1 F-6, 1 F-8) and 3 F series (3 F-4, 3 F-6, 3 F-8). Chemical structures and LC properties of the six symmetric LC dimers were characterised by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance hydrogen spectrometer (1H NMR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and polarised optical microscopy (POM). The 1 F series dimers only show nematic phase. While for 3 F series, smectic phase appeared, and with the increase of flexible spacers, the smectic phase is dominant. For the formation of smectic phase of 3 F series, the larger intermolecular transverse force coming from CF3 may be the driving force, and the long flexible spacer makes it possible. The melting temperatures of the 1 F series and 3 F series gradually decrease as the length of the flexible spacer increases, respectively, indicating that molecular rigidity has a greater influence on the melting temperatures. The melting temperatures of the 3 F series dimers decrease faster, which may attribute to the influence of CF3 on the conformation of the dimers. [ABSTRACT FROM AUTHOR]

A series of symmetric liquid crystal (LC) dimers with the same chiral core (S)-1-phenylethane-1,2-diol ((S)-PE) have been synthesised, termed TBDA-(S)-PE, 3F3B-(S)-PE, 3F2B-(S)-PE, 1F3B-(S)-PE, 1F2B-(S)-PE, respectively. Chemical structures and LC properties of the five symmetric LC dimers were characterised by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance hydrogen spectrometer (1H NMR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction (XRD) and polarised optical microscopy (POM). TBDA-(S)-PE displayed enantiotropic chiral smectic A (SmA*) phase while 3F3B-(S)-PE, 3F2B-(S)-PE, 1F2B-(S)-PE all displayed enantiotropic chiral nematic (N*) phase and 1F3B-(S)-PE displayed monotropic N* phase. The results indicated that the removal of the flexible spacers between the rigid mesogenic arm and the chiral core facilitated the formation of the N* phase. When the rigid mesogenic units are connected to the chiral core directly, the structure of the terminal fluorine group and the rigidity of the mesogenic unit played certain influence on the thermal properties of the LC dimers, but did not change the type of mesomorphic phase. Compared to 3F3B-(S)-PE and 1F3B-(S)-PE, 3F2B-(S)-PE and 1F2B-(S)-PE displayed wider LC ranges, respectively, suggesting molecular regularity had greater influence on LC-isotropic (I) transition temperature. [ABSTRACT FROM AUTHOR]

A new species of permineralized gymnosperm stem is described from volcaniclastic tuffs in Lopingian (late Permian) Xuanwei Formation from eastern Yunnan province, China. The stem comprises well-preserved tissues of the pith, primary and secondary xylem. Pith is divided into a thick-walled parenchymatous peripheral zone and an inner parenchymatous part. Primary xylem strands are numerous and indistinct with mesarch maturation. Secondary xylem is pycnoxylic with scalariform bordered pits on radial tracheid walls, with rays normally uniseriate or partly biseriate. Cross-field pits are mixed and including circular, elliptical and scalariform pitting. Comparisons indicate a close affinity with the contemporaneous plant Xuanweioxylon scalariforme , but differences with it lead to the erection of Xuanweioxylon damogouense sp. nov. We evaluate the systematic affinity of both species of Xuanweioxylon and conclude they represent conifers based on features of their wood anatomy. We consider the Xuanwei Formation includes at least four species of conifer, and show that X. damogouense possessed weak growth rings and false rings that suggest it grew in a climate with low seasonality and occasional periods of drought. • A new conifer stem is described from the Upper Permian of southwestern China. • A new species Xuanweioxylon damogouense sp. nov. is established. • The new species increases the diversity of Xuanweioxylon. [ABSTRACT FROM AUTHOR]

A series of non-symmetric liquid crystal (LC) dimers with the same chiral core 1,2-propanediol (PD) have been synthesised, termed as ABBA-PD-TFBA, PBBA-PD-TFBA, ABA-PD-TFBA, PBA-PD-TFBA and AA-PD-TFBA, respectively, in which one of the two mesogenic groups, the fluorinated mesogenic unit, was kept fix and the other arm was different. The intermediate compounds and LC dimers were characterised by FTIR, 1H NMR, differential scanning calorimetry, thermogravimetric analysis, polarised optical microscopy and X-ray diffractometer (XRD). The results of the measurements indicated that ABBA-PD-TFBA, PBBA-PD-TFBA and ABA-PD-TFBA displayed optical activity and enantiotropic chiral nematic phase, and PBA-PD-TFBA was an enantiotropic nematic LC while AA-PD-TFBA was a monotropic LC, displaying both nematic phase and smectic A phase on cooling. The results indicated that PD was able to induce the chiral nematic phase, nevertheless, the rigidity of the mesogenic arm, the flexibility of the terminal group and even the type of the terminal chemical bond played an important effect on the thermal properties of the dimers, and even on the formation of the chiral nematic phase. It is also worth noting that C=C at the terminal helped to stabilise the LC phase. [ABSTRACT FROM AUTHOR]