Nanostructured Liquid Crystals Research Articles

Mechanochromic and Conductive Chiral Nematic Nanostructured Film for Bioinspired Ionic Skins.

Chameleon skin is naturally adaptive and can sense environmental changes and transform sensing into bioelectrical and optical signals by manipulating ion transduction and photonic nanostructures. The increasing interest in mimicking biological skins has considerably promoted the development of advanced photonic materials with an increasing ionic conductivity. Herein, we report the judicious design and fabrication of a bioinspired mechanochromic chiral nematic nanostructured film with good ionic conductivity by infiltrating fluorine-rich ionic liquids (FILs) into a swollen self-assembled cellulose nanocrystal (CNC) film with helical nanoarchitectures. Notably, the introduction of 2-hydroxyethyl acrylate considerably enhances the compatibility of hydrophobic FILs and hydrophilic CNCs. The resulting FIL-CNC nanostructured films exhibited excellent mechanochromism, good ionic conductivity, and outstanding optical/electrical dual-signal sensing performance when used as a bioinspired ionic skin for real-time monitoring of human motions. Owing to the integration of FILs, the underwater stability of the chiral liquid crystal nanostructures of CNCs was significantly enhanced. Notably, underwater contact/contactless sensing modes and encrypted information transmission have been achieved with the FIL-CNC nanostructured film. This study can offer great insights for the advancement of biomimetic multifunctional artificial skins and emerging interactive devices, which can find important applications in wearable iontronics, human-machine interactions, and intelligent robots.

Reentrant 2D Nanostructured Liquid Crystals by Competition between Molecular Packing and Conformation: Potential Design for Multistep Switching of Ionic Conductivity.

The front cover artwork is provided by Takashi Kato at the University of Tokyo. The image shows three assembled structures of smectic liquid crystals that show reentrant behavior. Read the full text of the Research Article at 10.1002/cphc.202200927.

Front Cover: Reentrant 2D Nanostructured Liquid Crystals by Competition between Molecular Packing and Conformation: Potential Design for Multistep Switching of Ionic Conductivity (ChemPhysChem 8/2023)

The Front Cover shows three assembled structures of smectic liquid crystals that show reentrant behavior. More information can be found in the Research Article by Go Watanabe, Goran Ungar, Takashi Kato and co-workers.

Reentrant 2D Nanostructured Liquid Crystals by Competition between Molecular Packing and Conformation: Potential Design for Multistep Switching of Ionic Conductivity.

Reentrant phenomena in soft matter and biosystems have attracted considerable attention because their properties are closely related to high functionality. Here, we report a combined experimental and computational study on the self-assembly and reentrant behavior of a single-component thermotropic smectic liquid crystal toward the realization of dynamically functional materials. We have designed and synthesized a mesogenic molecule consisting of an alicyclic trans,trans-bicyclohexyl mesogen and a polar cyclic carbonate group connected by a flexible tetra(oxyethylene) spacer. The molecule exhibits an unprecedented sequence of layered smectic phases, in the order: smectic A-smectic B-reentrant smectic A. Electron density profiles and large-scale molecular dynamics simulations indicate that competition between the stacking of bicyclohexyl mesogens and the conformational flexibility of tetra(oxyethylene) chains induces this unusual reentrant behavior. Ion-conductive reentrant liquid-crystalline materials have been developed, which undergo the multistep conductivity changes in response to temperature. The reentrant liquid crystals have potential as new mesogenic materials exhibiting switching functions.

Phase behavior of soybean phosphatidylcholine and glycerol dioleate in hydrated and dehydrated states studied by small-angle X-ray scattering.

Soybean phosphatidylcholine (SPC) and glycerol dioleate (GDO) form liquid crystal nanostructures in aqueous environments, and their mixtures can effectively encapsulate active pharmaceutical ingredients (API). When used in a subcutaneous environment, the liquid crystalline matrix gradually hydrates and degrades in the tissue whilst slowly releasing the API. Hydration dependent SPC/GDO phase behavior is complex, non-trivial, and still not fully understood. A deeper understanding of this system is important for controlling its function in drug delivery applications. The phase behavior of the mixture of SPC/GDO/water was studied as a function of hydration and lipid ratio. Small-angle X-ray scattering (SAXS) was used to identify space groups in liquid crystalline phases and to get detailed structural information on the isotropic reverse micellar phase. The reported pseudo ternary phase diagram includes eight different phases and numerous multiphase regions in a thermodynamically consistent way. For mixtures with SPC as the predominant component, the system presents a reverse hexagonal, lamellar and R3m phase. For mixtures with lower SPC concentrations, reverse cubic (Fd3m and Pm3n) as well as intermediate and isotropic micellar phases were identified. By modeling the SAXS data using a core-shell approach, the properties of the isotropic micellar phase were studied in detail as a function of concentration. Moreover, SAXS analysis of other phases revealed new structural features in relation to lipid-water interactions. The new improved ternary phase diagram offers valuable insight into the complex phase behavior of the SPC/GDO system. The detailed structural information is important for understanding what APIs can be incorporated in the liquid crystal structure.

Development and optimization of amphiphilic self-assembly into nanostructured liquid crystals for transdermal delivery of an antidiabetic SGLT2 inhibitor

The anti-hyperglycemic sodium glucose co-transporter 2 inhibitor Canagliflozin (CFZ) represents a recent antihyperglycemic modality, yet it suffers from low oral bioavailability. The current work aims to formulate CFZ-loaded transdermal nanostructured liquid crystal gel matrix (NLCG) to improve its therapeutic efficiency. Pre-formulation study included the construction of pseudoternary phase diagrams to explore the effect of two conventional amphiphiles against amphiphilic tri-block copolymer in the formulation of NLCG. The influence of different co-solvents was also investigated with the use of monooleine as the oil. Physical characterization, morphological examination and skin permeation were performed for the optimized formulations. The formula of choice was further investigated for skin irritation and chemical stability. Pharmacodynamic evaluation of the successful formula was conducted on hyperglycemic as well as normoglycemic mice. In addition, oral glucose tolerance test was conducted. Results revealed the supremacy of Poloxamer for stabilizing and maximizing liquid crystal gel (LCG) area percentage that reached up to 12.6%. CFZ-NLCG2 isotropic formula showed the highest permeation parameters; maximum flux value of 7460 μg/cm2 h and Q 24 of 5327 μg/cm2. Pharmacodynamic evaluation revealed the superiority of the antihyperglycemic activity of CFZ-NLCG2 in fasting mice and its equivalence in the oral glucose tolerance test (OGTT) compared to the oral one. The obtained results confirmed the success of CFZ-NLCG2 in the transdermal delivery of CFZ in therapeutically effective concentration compared to the oral route, bypassing first pass effect; in addition, eliminates the possible gastrointestinal side effects related to the inhibition of intestinal sodium glucose co-transporter (SGLT) and maximizes its selectivity to the desired inhibition of renal SGLT.

The characterization of hexagonal lyotropic liquid crystal nanostructure: effects of polymer tail length

The characterization of hexagonal lyotropic liquid crystal nanostructure: effects of polymer tail length

Optimizing the performance of the near-infrared (NIR) photothermal conversion via modulating the domain size of the chiral nematic phase in co-assembled cellulose nanocrystal composite films

The self-assembled liquid crystal nanostructure of CNCs provides an effective phase-segregation for PEDOT, thus improving the NIR photothermal performance of CNCs/PEDOT:PSS/OS/TA composites significantly.

Collagen Pentablock Copolymers Form Smectic Liquid Crystals as Precursors for Mussel Byssus Fabrication.

Protein-based biological materials are important role models for the design and fabrication of next generation advanced polymers. Marine mussels (Mytilus spp.) fabricate hierarchically structured collagenous fibers known as byssal threads via bottom-up supramolecular assembly of fluid protein precursors. The high degree of structural organization in byssal threads is intimately linked to their exceptional toughness and self-healing capacity. Here, we investigated the hypothesis that multidomain collagen precursor proteins, known as preCols, are stored in secretory vesicles as a colloidal liquid crystal (LC) phase prior to thread self-assembly. Using advanced electron microscopy methods, including scanning TEM and FIB-SEM, we visualized the detailed smectic preCol LC nanostructure in 3D, including various LC defects, confirming this hypothesis and providing quantitative insights into the mesophase structure. In light of these findings, we performed an in-depth comparative analysis of preCol protein sequences from multiple Mytilid species revealing that the smectic organization arises from an evolutionarily conserved ABCBA pentablock copolymer-like primary structure based on demarcations in hydropathy and charge distribution as well as terminal pH-responsive domains that trigger fiber formation. These distilled supramolecular assembly principles provide inspiration and strategies for sustainable assembly of nanostructured polymeric materials for potential applications in engineering and biomedical applications.

Design and Characterization of Glyceryl Monooleate-Nanostructures Containing Doxorubicin Hydrochloride.

Glyceryl monooleate (GMO) is one of the most popular amphiphilic lipids, which, in the presence of different amounts of water and a proper amount of stabilizer, can promote the development of well defined, thermodynamically stable nanostructures, called lyotropic liquid crystal dispersions. The aim of this study is based on the design, characterization, and evaluation of the cytotoxicity of lyotropic liquid crystal nanostructures containing a model anticancer drug such as doxorubicin hydrochloride. The drug is efficiently retained by the GMO nanosystems by a remote loading approach. The nanostructures prepared with different non-ionic surfactants (poloxamers and polysorbates) are characterized by different physico-chemical features as a function of several parameters, i.e., serum stability, temperature, and different pH values, as well as the amount of cryoprotectants used to obtain suitable freeze-dried systems. The nanostructures prepared with poloxamer 407 used as a stabilizer show an increased toxicity of the entrapped drug on breast cancer cell lines (MCF-7 and MDA-MB-231) due to their ability to sensitize multidrug-resistant (MDR) tumor cells through the inhibition of specific drug efflux transporters. Moreover, the interaction between the nanostructures and the cells occurs after just a few hours, evidencing a huge cellular uptake of the nanosystems.

A Vaccine Based on Kunitz-Type Molecule Confers Protection Against Fasciola hepatica Challenge by Inducing IFN-γ and Antibody Immune Responses Through IL-17A Production.

Fasciola hepatica is helminth parasite found around the world that causes fasciolosis, a chronic disease affecting mainly cattle, sheep, and occasionally humans. Triclabendazole is the drug of choice to treat this parasite. However, the continuous use of this drug has led to the development of parasite resistance and, consequently, the limitation of its effectiveness. Hence, vaccination appears as an attractive option to develop. In this work, we evaluated the potential of F. hepatica Kunitz-type molecule (FhKTM) as an antigen formulated with a liquid crystal nanostructure formed by self-assembly of 6-O-ascorbyl palmitate ester (Coa-ASC16) and the synthetic oligodeoxynucleotide containing unmethylated cytosine-guanine motifs (CpG-ODN) during an experimental model of fasciolosis in mice, and we further dissected the immune response associated with host protection. Our results showed that immunization of mice with FhKTM/CpG-ODN/Coa-ASC16 induces protection against F. hepatica challenge by preventing liver damage and improving survival after F. hepatica infection. FhKTM/CpG-ODN/Coa-ASC16-immunized mice elicited potent IFN-γ and IL-17A with high levels of antigen-specific IgG1, IgG2a, and IgA serum antibodies. Strikingly, IL-17A blockade during infection decreased IgG2a and IgA antibody levels as well as IFN-γ production, leading to an increase in mortality of vaccinated mice. The present study highlights the potential of a new vaccine formulation to improve control and help the eradication of F. hepatica infection, with potential applications for natural hosts such as cattle and sheep.

An all-solid-state lamellar-nanostructured polymer electrolyte in-situ-prepared from smectic liquid crystal for thermally stable dye-sensitized solar cells

A novel all-solid-state polymer electrolyte based on thiolate/disulfide redox couple was in-situ prepared from a lamellar-assembled liquid crystal precursor for dye-sensitized solar cells (DSSCs). The use of the thiolate/disulfide redox couple allowed the in-situ polymerization, which ensured both preservation of the lamellar nanostructure in electrolyte and sufficient interfacial contact in DSSC. Electrochemical analysis revealed that the lamellar-nanostructured electrolyte possessed charge transport ability and photovoltaic performance quite close to the liquid crystal electrolyte precursor. The resultant all-solid-state DSSCs showed a thermally stable photovoltaic performance with PCE higher than 2% from 35 to 90 °C. The method in using in-situ polymerization of nanostructured liquid crystals to prepare solid-state electrolytes shed a new light for efficient and stable all-solid-state DSSC preparation, especially in large-scale actual application.

Transport of Ions, Electrons and Molecules in Nanostructured Liquid Crystals for Their New Applications

Transport of Ions, Electrons and Molecules in Nanostructured Liquid Crystals for Their New Applications

Transport of Ions, Electrons and Molecules in Nanostructured Liquid Crystals for Their New Applications

Transport of Ions, Electrons and Molecules in Nanostructured Liquid Crystals for Their New Applications

Paper-like flexible optically isotropic liquid crystal film for tunable diffractive devices.

We have demonstrated a paper-like diffractive film in which nano-structured liquid crystal droplets are embedded in elastomeric monomer incorporated polymer matrix by polymerization induced phase-separation. The film with voltage-tunable phase grating exhibits an optically isotropic phase with high transparency and an effective chromatic diffraction for an incident white light with sub-millisecond switching time. In addition, the proposed diffractive film is exhibiting excellent chemical stability against organic and inorganic solvents. In this paper, the diffraction properties of test films depending on incident polarization direction, wavelength, and spatial dispersion are characterized. Easy processing and optically isotropic nature of the film imparts potential applications to flexible electro-optic devices that can be widely implemented in wearable photonics.

Formulating stable hexosome dispersions with a technical grade diglycerol-based surfactant

We report on the phase behavior of a technical grade and commercially available diglycerol monoisostearate, C41V, and its use for the preparation of nanostructured liquid crystal dispersions (hexosomes). C41V in water forms a reverse hexagonal liquid crystal at room temperature and in a wide range of concentrations (0.5–95 wt%); this hexagonal liquid crystal is stable up to 70 °C. A simple and effective method has been developed to disperse hexosomes with an encapsulated active molecule (Ketoprofen) that consists of (1) producing a nano-emulsion stabilized by an amphiphilic block copolymer (Pluronic F127) and containing ethyl acetate and C41V by using ultrasounds and (2) evaporating the solvent to produce hexosomes. The size of the hexosomes and ultrasound dispersion time is markedly reduced by using ethyl acetate as an auxiliary solvent with an optimal initial ratio of C41V:ethyl acetate of 50:50. Dynamic light scattering shows that the size of the hexosomes decreases as the concentration of stabilizer F127 or encapsulated Ketoprofen is increased. The lattice parameter in the hexagonal structure is calculated from small angle scattering data to be ca. 5.3 nm and is only slightly dependent on the amount of F127 and/or encapsulated Ketoprofen. Cryo electron microscopy reveals that the samples contain hexosomes and these coexist with spherical, likely F127 micelles. Lastly, hexosomes show a pH responsive release of Ketoprofen which could be useful for target delivery in the gastrointestinal tract.

Liquid Crystalline Nanocolloids for the Storage of Electro-Optic Responsive Images.

Liquid crystalline nanocolloids (LCNCs), which are nanostructured composites comprising nanoparticles (NPs) and a liquid crystal (LC) host, have attracted a great deal of attention because of their promising new fundamental physical behaviors and functional properties. Yet, it still remains a big challenge to pattern LCNCs into mesoscale-ordered structures due to the limited NP loading in the LC host. Here, we demonstrate LCNCs in the nematic phase with a high NP loading (∼42 wt %) by in situ co-functionalizing the NP with alkyl and mesogenic ligands. The LCNCs can be assembled into ordered structures through holographic photopolymerization-induced phase separation, giving rise to holographic polymer-dispersed nematic nanocolloids (HPDNNC). Interestingly, high diffraction efficiency, low light-scattering loss, and unique electric-switchable capability are realized in the HPDNNC. In addition, high-quality switchable and unclonable colored images are reconstructed, promising a host of advanced applications (e.g., anticounterfeiting). Our findings pave a way to advance the fundamental understanding of nanostructured LCs and their practical utility in enabling a new breed of inorganic-organic composite materials.

Fabrication of pixelated liquid crystal nanostructures employing the contact line instabilities of droplets.

A liquid crystal (LC) droplet resting on a poly-dimethylsiloxane substrate could rapidly spread upon solvent vapour annealing to form a non-uniform film. While the solvophobic surfaces restricted the spreading of the droplet to form a thicker film upon solvent annealing, the solvophilic substrates allowed the formation of a thinner film under similar conditions. Withdrawal of the solvent exposure caused rapid evaporation of the solvent molecules from the film, especially near the retracting contact-line to form microscale LC-droplets, which shrunk into nanoscopic ones after evaporation of the excess solvent. The thinner films on solvophilic surfaces allowed the formation of droplets with smaller size and periodicity as small as ∼100 nm and ∼200 nm, respectively. Furthermore, the use of a patterned substrate could impose a large-area ordering on the nanodroplets. A theoretical model for an evaporating film of LC-solution revealed that the spacing of nanodroplets could be decided by the interplay of stabilizing and destabilizing components of capillary force while van der Waals interaction played a supportive role when the film was ultrathin near the contact line. The micro/nanodroplets thus formed showed an anomalous oscillatory rotational motion originating from the difference in the Laplace pressure near contact lines under the influence of an external electric field. The application of the Lorenz force to these droplets showed translation and rotational motions followed by ejection of satellite droplets.

Nature-Inspired Emerging Chiral Liquid Crystal Nanostructures: From Molecular Self-Assembly to DNA Mesophase and Nanocolloids.

Liquid crystals (LCs) are omnipresent in living matter, whose chirality is an elegant and distinct feature in certain plant tissues, the cuticles of crabs, beetles, arthropods, and beyond. Taking inspiration from nature, researchers have recently devoted extensive efforts toward developing chiral liquid crystalline materials with self-organized nanostructures and exploring their potential applications in diverse fields ranging from dynamic photonics to energy and safety issues. In this review, an account on the state of the art of emerging chiral liquid crystalline nanostructured materials and their technological applications is provided. First, an overview on the significance of chiral liquid crystalline architectures in various living systems is given. Then, the recent significant progress in different chiral liquid crystalline systems including thermotropic LCs (cholesteric LCs, cubic blue phases, achiral bent-core LCs, etc.) and lyotropic LCs (DNA LCs, nanocellulose LCs, and graphene oxide LCs) is showcased. The review concludes with a perspective on the future scope, opportunities, and challenges in these truly advanced functional soft materials and their promising applications.

Functional liquid-crystalline polymers and supramolecular liquid crystals

The design and functions of liquid-crystalline (LC) polymers with classifying them into conventional-, supramolecular-, dendritic- and network-type LC polymers are described. LC polymers show new functions as new devices in the field of energy and environment by incorporating mesogenic moieties exhibiting photonic, electronic and ionic functions. Supramolecular LC polymers show dynamic and unique properties because the mesogenic moieties are built with non-covalent interactions. Dendritic-type LC polymers exhibit liquid crystallinity by nanosegregation of aromatic and aliphatic moieties. Dendritic fork-like mesogens have also been prepared. A variety of nonmesogeic functional building blocks including fullerene, π-conjugated moieties, catenane, rotaxane and others can be incorporated into LC phases by attaching these dendritic moieties. LC networks are constructed in situ polymerization of polymerizable nematic or nanostructured liquid crystals. The specific characteristics of the LC networks have generated new research trends to develop well-defined polymers that exhibit optical, transport and separation properties. In these materials, through suitable design of LC monomers, the preservation of smectic, columnar and bicontinuous cubic phases has been successfully used for the development of membranes with one-dimensional, two-dimensional and three-dimensional nanostructures. The design and functions of various liquid-crystalline (LC) polymers including main-chain, side-chain and network LC polymers as well as dendritic structures are described. These polymeric LC materials can be applied for electro-, ion-, photo-active materials as well as mechanically tough materials. The introduction of supramolecular design has also generated a new category of functional LC materials.