In this Communication, we develop a two-step acyclic diene metathesis in situ polymerization/cross-linking method to synthesize uniaxially aligned main-chain liquid crystal elastomers with chemically bonded near-infrared absorbing four-alkenyl-tailed croconaine-core cross-linkers. Because of the extraordinary photothermal conversion property, such a soft actuator material can raise its local temperature from 18 to 260 °C in 8 s, and lift up burdens 5600 times heavier than its own weight, under 808 nm near-infrared irradiation.

The development of pure polymeric films with anisotropic thermal conductivities for electronic device packaging applications has attracted intense scientific attention. In order to enhance the polymeric film's normal-direction thermal conductivity, homeotropic alignment of macromolecular chains is the primary concern. One of the promising preparation strategies is to perform in situ photopolymerization of homeotropic-oriented liquid crystal monomers. In this work, we design and synthesize a novel tolane-core thiol–ene-tailed liquid crystal monomer. Benefitting from the conjugated and extended tolane π-system of the mesogenic core and length extension of the terminal aliphatic tails, the normal-to-plane thermal conductivity value and the thermal conductivity anisotropy value of the corresponding cross-linked main-chain end-on liquid crystal polymer (xMELCP) film reach 3.56 W m−1 K−1 and 15.0, respectively. Compared with the data of a previously reported ester-type thiol–ene xMELCP film, the two primary values of this novel tolane-type thiol–ene xMELCP material are increased dramatically by 46% and 29%, respectively.

Recognition of melamine is not only of importance for the food industry but also an interesting scientific research topic. The objective of this work is to screen suitable hydrogen-bonding complementary compounds for the construction of melamine-core supramolecular discotic liquid crystal (LC) materials which might provide a LC perspective for detection and separation of melamine in the future. We design and synthesize five categories of long-alkyl-tailed compounds bearing different hydrogen-bonding complementary functional groups, including benzoic acid, cyanuric acid, homophthalimide, succinimide and thymine derivatives. The experimental results demonstrate that the imidodicarbonyl unit is the best hydrogen-bonding complementary functional group of melamine. Furthermore, the heterocyclic ring size markedly influences the hydrogen-bonding strength of the melamine-imidodicarbonyl unit complex. Most importantly, liquid crystallinity can be generated from these hydrogen-bonding supramolecular complexes. In particular, a variety of columnar mesomorphic orders (such as hexagonal columnar, rectangular columnar, and square columnar phases) can be effectively achieved by functionalization of thymine or succinimide units and modulation of the molar ratios of melamine and these hydrogen-bonding complementary compounds.

In this communication, we describe a two-stage temperature-varied photopatterning protocol to synthesize a series of single-layer dual-phase liquid crystalline elastomer films, which have the capabilities to perform versatile three-dimensional motions, such as bending, accordion-folding, wrinkling, curling, and buckling, under thermal stimulus.

Monodomain liquid crystalline elastomers (LCEs) with anisotropic, loosely crosslinked polymeric matrices have attracted intense scientific attention due to their widespread applications in stimuli-responsive soft actuators. However, traditional synthetic pathways towards monodomain LCEs require complicated procedures, elevated reaction temperatures, and a prolonged preparation time ranging from several hours to even several days. In this manuscript, we report a fast room-temperature one-pot, two-stage thiol–ene photoaddition method to synthesize monodomain polysiloxane-based LCE films. The first stage is a partial thiol–ene photo-crosslinking of poly(3-mercaptopropylmethylsiloxanes) and vinyl-terminated mesogens and crosslinkers in solution, the second stage is a complete thiol–ene photo-crosslinking of the uniaxially-stretched pre-crosslinked LCE film. Starting from mesogenic monomers, the whole preparation process can be finished in less than 30 minutes, and all the preparation experiments are performed at room temperature, in open air. We believe that this facile one-pot, two-stage thiol–ene photoaddition method can open a new route for the fast and robust production of monodomain LCE shape memory materials.

In this work, we report the first example of a calamitic mesogenic near-infrared (NIR) absorbing organic dye, made by functionalizing a thiophene–croconaine chromophore rigid core with two symmetric long flexible alkyl chains. The liquid crystal (LC) NIR dye YHD796 exhibits a sharp and intense NIR absorption band with a maximum absorption peak at 796 nm. Taking advantage of the improved solubility of YHD796 dispersed in mesogenic molecules, a homogeneously-aligned mono-domain liquid crystalline elastomer (LCE)/YHD796 composite film is successfully prepared by applying the classical LC-cell-alignment method and in situ photo-polymerization of photocurable LC monomer mixtures. This LCE/YHD796 composite film performs a fully reversible contraction/expansion response towards NIR light stimulus due to the photo-thermal heating effect induced by the YHD796 dye well-dispersed in the LCE matrix.

Homeotropically-aligned main-chain and side-on liquid crystalline elastomer films are prepared by using LC thiol–ene and acrylate systems respectively. Evaluated by laser flash analysis, the room temperature thermal conductivities of these two LCP films in the film normal direction are both dramatically higher than those along the horizontal direction.

The known synthetic methods of preparing main-chain liquid crystalline polymers (MCLCPs) are rather limited to several polycondensation reactions. However, the nature of step-growth polycondensation endows the corresponding MCLCPs with relatively low molecular weights and broad molecular weight distributions. In this manuscript, an entropy-driven ring-opening metathesis polymerization (ED-ROMP) approach is for the first time applied in producing a MCLCP by polymerizing a macrocyclic olefin monomer containing one cyclohexanecarboxylic acid phenyl ester group as a mesogenic core and one icos-10-enedicarbonyl group as a flexible aliphatic chain. For comparison, Yamaguchi macrolactonization and ring-closing metathesis (RCM) methods are used to synthesize the macrocyclic olefin monomer, and it turns out that although the macrolactonization method can prepare a pure macrocyclic monomer, the RCM strategy is advantageous in providing a much higher overall reaction yield. Furthermore, compared with a traditional acyclic diene metathesis (ADMET) polymerization of mesogenic α,ω-diene, the ED-ROMP approach starting with the same monomer-to-catalyst ratio, releases no heat or volatiles during the reaction, and can efficiently provide MCLCPs with much higher molecular weights over a shorter reaction time.

A series of new columnar liquid crystals containing an adamantane central unit with its four bridgehead positions partially or fully decorated with different numbers (1–4) of 3,4,5-tris(dodecyloxy)phenyl carbamoyl groups were designed and investigated carefully to explore the structure–property correlations. The molecular structures and mesomorphic properties of the DLCs were characterized by 1H-NMR, 13C-NMR, IR, UV-vis, POM, DSC and XRD. It was found that the mesophase symmetry and thermal stability were extremely dependent on the structures of the adamantane derivatives. No mesophase was observed for the 1-adamantanecarboxylic acid derivative ADLC1, while two different mesophases were observed for ADLC2, a 1,3-disubstituted derivative functionalized with two 3,4,5-tris(dodecyloxy)phenyl carbamoyl groups at two symmetric bridgehead positions. At lower temperature ADLC2 exhibited a rectangular columnar phase, which switched to a square columnar phase possessing a wide temperature range. Similarly, a hexagonal columnar mesophase was observed for the bridgehead trisubstituted adamantane molecule ADLC3. Interestingly, the fully bridgehead-functionalized 1,3,5,7-tetrasubstituted adamantane compound ADLC4 completely lost liquid crystallinity.

In this work, we report the first example of uniaxial aligned conjugated polymer (CP)/liquid crystalline elastomer (LCE) composite material by doping polyaniline nanoparticles into a classical monodomain polysiloxane-based LCE matrix. A series of comparative experiments are performed to investigate the photoresponsive properties of these polyaniline/LCE samples in correspondence to the two different conjugation forms (emeralidine salt (ES) or emeralidine base (EB)) and the varied doping concentrations (0.5 or 1.0 wt %) of the incorporated polyaniline nanoparticles. Taking advantage of the excellent photothermal conversion efficiency, these novel polyaniline/LCE composite materials can lift up ca. 200 times their own weights under the NIR illumination driving force, and such a photostimulated muscle-like actuation behavior is fully reversible after NIR light is removed.

In this work, aiming to combine thermal-induced LC-to-isotropic phase transition effect, azobenzene’s trans–cis tautomerization effect and the photothermal effect into one liquid crystalline elastomer (LCE) system to prepare a heat/UV/near-infrared(NIR) triple-stimuli-responsive LCE material, we design and synthesize a polysiloxane-based side-chain side-on azobenzene-containing LCE matrix embedded with 1 wt % single-walled carbon nanotubes, through Finkelmann’s two-step cross-linking process coupled with a uniaxial stretching technique. The multistimuli responsive behaviors of this LCE/CNT composite film are investigated under different external stimuli (heat, UV, NIR). The composite film can realize a reversible deformation between contraction and extension under heating/cooling cycles. Moreover, the composite film can perform an impressive three-dimensional deformation (bending) under UV-light irradiation. On the contrary, long wavelength light (NIR laser) forces the composite film into shrinking instead of bending. Most importantly, the shape transformations (three-dimensional bending vs two-dimensional shrinking) of this novel shape memory material can be tuned by the light wavelength (UV vs NIR), which might endow this LCE material with potential applications in control devices and logic gate devices, etc.

A novel NIR-responsive GNR/LCE composite fiber material was prepared by a three-step sequential thiol-click chemistry approach. Taking advantage of GNRs' significant photo-thermal effect, a GNR/LCE composite material with a very low Au loading-level (0.09 wt%), under 808 nm NIR stimulus achieved the N-to-I transition and shrank dramatically in an ambient environment.

Most of the traditional chiral side-chain liquid crystalline polymers (SCLCPs) depend on pendant chiral mesogenic units to introduce chirality into their structure, with the polymer backbones being usually achiral. In this work, we asymmetrically synthesize several enantiomerically pure norbornene monomers functionalized with achiral mesogenic units, and further apply a ring-opening metathesis polymerization technique to prepare a series of side-on and end-on SCLCPs with an optically active polynorbornene main chain and achiral mesogens. Their physical properties are fully characterized by NMR, UV, CD, GPC, TGA, DSC, polarimetry, polarized optical microscopy and small-angle X-ray scattering. The obtained side-on SCLCPs display the tendency to form nematic, i.e. achiral mesophases, in strong contrast to the chiral nematic (cholesteric) mesophase exhibited by their comparative end-on analogues. The proposed explanation for this phenomenon is that the chiral backbones and the laterally attached mesogens of side-on SCLCPs can concurrently exist in a parallel arrangement so that the mesogenic directors might not be affected by the chirality information, while the mesogenic directors of end-on SCLCPs always tilt to the backbone orientation so that the twisting power of chiral main chains might force the terminally attached mesogens to form helical structures.

This manuscript presents a facile thiol–ene photo-click chemistry method to prepare magnetic stir bar-encapsulated polysiloxane-based organocatalyst gels under benign conditions, and develops a Stir Bar-Encapsulated Catalysis (SBEC) technique. Through thiol–ene addition chemistry, we graft olefin-terminated organocatalysts (i.e. MacMillan catalyst, proline catalyst, and N-heterocyclic carbene catalyst) onto poly[3-mercaptopropylmethylsiloxane], which is further photo-crosslinked to coat the embedded magnetic stir bar. The prepared magnetic stir bar-encapsulated polysiloxane-based organocatalyst gels can be put into reaction flasks to perform stirring and catalysis functions at the same time. The most important benefit of SBEC technique is to infinitely simplify the catalyst/product separation procedure by using a simple stir-bar-retriever, even without any precipitation/filtration steps. The catalytic performances of three different organocatalyst gels applied in asymmetric Diels–Alder reaction, asymmetric aldol reaction and benzoin condensation reaction respectively are also examined herein.

We describe in this work an alkyne-hydrosilylation approach to synthesize a series of novel polysiloxane side-chain LCPs attaching end-on or side-on mesogenic side groups. Their properties are characterized by NMR, FTIR, gel permeation chromatography, thermogravimetric analysis, differential scanning calorimetry, polarized optical microscopy and small-angle X-ray scattering. These obtained alkenylsilane linked novel LCPs exhibit higher glass transition temperatures and clearing points, and especially display the tendency of forming smectic phases, in strong contrast with the nematic phases of their comparative conventional alkylsilane linked analogues, which manifests more rigid features of the alkenylsilane linkages and their significant influence on the mesomorphic properties.

In this communication, we describe a two-stage temperature-varied photopatterning protocol to synthesize a series of single-layer dual-phase liquid crystalline elastomer films, which have the capabilities to perform versatile three-dimensional motions, such as bending, accordion-folding, wrinkling, curling, and buckling, under thermal stimulus.

Homeotropically-aligned main-chain and side-on liquid crystalline elastomer films are prepared by using LC thiol–ene and acrylate systems respectively. Evaluated by laser flash analysis, the room temperature thermal conductivities of these two LCP films in the film normal direction are both dramatically higher than those along the horizontal direction.

A novel NIR-responsive GNR/LCE composite fiber material was prepared by a three-step sequential thiol-click chemistry approach. Taking advantage of GNRs' significant photo-thermal effect, a GNR/LCE composite material with a very low Au loading-level (0.09 wt%), under 808 nm NIR stimulus achieved the N-to-I transition and shrank dramatically in an ambient environment.