Kwang-Un Jeong

Chonbuk National University | cbnu

Many studies on the basis of cholesteric liquid crystal (CLC) have focused on dynamic optical changes utilizing photochemical reactions raising helical pitch variations. However, the conventional dyes doped in CLC system often show reversible isomerization such as trans‐cis, E‐Z, and open‐close forms that hampers the fixation of desired color cues....

Chiroptical 3D Actuators In article number 2210680, Kwang‐Un Jeong, Seung‐Yeol Jeon, Dae‐Yoon Kim, and co‐workers develop chiroptical 3D smart actuators by assembling cholesteric liquid crystals onto a polymeric gel thin film. Various reversible motions of chiroptical 3D smart actuators are performed by swelling and deswelling of the programmed Jan...

Photonic Crystal Papers In article number 2206764, Dae‐Yoon Kim, Kwang‐Un Jeong, and co‐workers develop 1D stripe and 2D wavy wrinkled photonic crystal papers to demonstrate consistent reflection of colors regardless of viewing angle. The nanoscale molecular self‐assembly of cholesteric liquid crystal is combined with a microscale corrugated surfac...

Monofilament type of polyaromatic amide (PA) and carbon nanotube (CNT) composite fibers is presented. A concept of a lyotropic liquid crystal (LLC) constructed via a spontaneous self-assembly is introduced to mitigate the extremely low compatibility between PA and CNT. These approaches provide an effective co-processing route of PA and CNT simultan...

Light manipulation strategies of nature have fascinated humans for centuries. In particular, structural colors are of considerable interest due to their ability to control the interaction between light and matter. Here, wrinkled photonic crystal papers (PCPs) is fabricated to demonstrate the consistent reflection of colors regardless of viewing ang...

Examples of anisotropic movement paired with helical geometry abound in the animal and plant kingdoms are used for a variety of reasons, such as diverse social signaling directed at conspecifics or camouflage to avoid predation. Inspired by these natural phenomena, a smart sensor is developed with a chiroptical 3D actuator that can fold, bend, and...

The growing spread of pathogens, caused by anthropogenic activities, pushes the interest of the scientific community towards developing biosensors with improved performance for rapid, simple, and on-site pathogen detection. In this study, we present and discuss a label-free gold nanorod (Au NR) array for the rapid detection of Escherichia coli cell...

Surface wrinkling enabled by interfacial instability is a facile and straightforward way to manipulate the physical properties of surfaces. Wrinkles are typically formed on mechanically heterogeneous bilayers by compressive stress arising from mismatch in the thermal expansion of individual layers upon thermal treatment. The ability of polymeric bi...

Kwang‐Un Jeong and co‐workers (article number 2200405) present a smart optical film with a programmed cyanostilbene‐based aggregation‐induced emission luminogen (AIEgen). The optical properties of the AIEgen are reversibly modulated by temperature change and light irradiation. The AIEgen exhibits time‐dependent optical changes, resulting from its u...

For the development of optically encryptable smart glass that can control the molecular alignment of liquid crystals (LCs), an azobenzene-based reactive molecule (ARM) capable of trans-cis photoisomerization is newly designed and synthesized. Photo-triggered LC-commandable smart glasses are successfully constructed by the surface functionalization...

The optical properties of newly synthesized cyanostilbene‐based AIEgen (D4CS) exhibiting a unique monotropic phase transition are modulated by engineering molecular packing structure and molecular conformation through temperature change and light irradiation. D4CS exhibits only a low‐ordered smectic liquid crystal (SmA) phase over a wide temperatur...

An anisotropic light emitting metallomesogen (PtM) consisting of a cyclometalated platinum(II)–terpyridine (Pt(II)–tpy) chromophore and a flexible dendron is newly synthesized as a thermal‐induced and polarization‐induced solid‐state luminescence switching material. The self‐assembled PtM is uniaxially aligned by mechanical shearing within the meso...

Metallomesogens In article number 2106559, Kwang‐Un Jeong and co‐workers present a luminescence switching material using cyclometalated Pt(II)‐based metallomesogen. The metallomesogen changes solid‐state emission in response to thermal stimulation and the uniaxially aligned metallomesogen presents linearly polarized photoluminescence. Metallomesoge...

An advanced heat managing graft polymer (AHG) was fabricated by introducing a mesogen-based molecular building block that facilitates photon transfer. The fabricated AHGs exhibit excellent thermal conductivity as well as...

In response to human damage caused by harmful vapors emitted throughout the industry, the detection of toxic vapors such as acid vapors is urgently required. Recognizing acid vapor leaks is...

To explore a new family of organic ionic materials, a series of α,ω-bis[N,N’-(4-alkylpyridinium)]alkane salts combined with iodide (I⁻), tetrafluoroborate (BF4⁻), and bis(trifluoromethanesulfonyl)imide (Tf2N⁻) anions and alkylene bridges of different lengths are synthesized. From ¹H NMR chemical shift changes, the proton acidity of at the bis-pyrid...

The flexible electrochromic Zn‐ion battery (FE‐ZiB), a newly born energy‐storage technology having both electrochromic characteristics and energy‐storage capability in a single device, will be a promising technology for the future transparent wearable electronics. However, the current technology limits the fabrication of FE‐ZIB because the zinc (Zn...

We report and discuss our first efforts devoted to realizing an innovative and miniaturized nanotechnology-based biosensor capable of real-time detect and quantify the presence of harmful pathogens dispersed in potable water. Gold nanorods, selected for their colorimetric sensitivity to the refractive index change, are functionalized, via the elect...

A self-crosslinkable side-chain liquid crystal polysiloxane containing cyanostilbene (Si-CSM) was newly synthesized for the development of a new generation of flexible optical paints. The photoisomerization of the cyanostilbene moiety at the molecular level was transferred and amplified to the phase transition of Si-CSM, resulting in changes in the...

Utilizing a newly programmed and synthesized heat storage mesogen (HSM) and reactive mesogen (RM), advanced heat managing polymer alloys that exhibit high thermal conductivity, high latent heat, and phase transition at high temperatures were developed for use as smart thermal energy harvesting and reutilization materials. The RM in the heat-managin...

The development of smart inks that change color and transparency in response to external stimuli is very important for various fields, from modern art to safety and anticounterfeiting technology. A uniaxially oriented diacetylene thin film on a macroscopic area is obtained by coating, self‐assembling and topochemical photopolymerizing of imidazoliu...

The development of smart inks that change color and transparency in response to external stimuli is important in safety and anticounterfeiting. In article number 2003980, Kwang‐Un Jeong and co‐workers demonstrate that a secret code, written with thermoresponsive and polarization‐dependent secret inks consisting of imidazolium‐functionalized diacety...

With the significance of heat management, recently, high thermal conducting polymers have attracted attention as promising polymeric matrix materials in miniaturized and flexible devices. Porphyrin-based reactive metallomesogens (PorV-x; x = -2H, -Ni, -Cu, and -Zn) were newly designed and synthesized for the fabrication of thermal conducting polyme...

Self-assembly control of supramolecular dyes is a challenging research field to generate programmed hierarchical superstructures with various shapes and dimensions that are closely related to their physical properties. The highly ordered thin film prepared by recrystallizing an azobenzene-based amphiphilic molecule (A1GC) provides a gold-like color...

Bandwidth-tunable anisotropic spatial light modulators are fabricated with redox-responsive dichroic mesogens. By in-troducing an ionic group and a polymerizable group into the chromophore, the programmed reactive mesogen (PDI-MA) exhibits a lyotropic chromonic liquid crystal (LCLC) phase. PDI-MA molecule forms a stable aromatic dianion state so th...

The physical properties of supramolecular soft materials strongly depend on the molecular packing structures constructed by thermodynamically and kinetically controlled molecular self-assembly. To investigate the relationship between molecular function and self-assembled molecular packing structure, a series of diacetylene (DA)-based supramolecules...

Liquid crystal elastomers (LCEs) are a unique class of active materials with the largest known reversible shape transformation in the solid state. The shape change of LCEs is directed by programming their molecular orientation, and therefore, several strategies to control LC alignment have been developed. Although mechanical alignment coupled with...

Smart windows are very attractive because they not only provide comfortable indoor conditions for cars and buildings, but also protect privacy. However, current smart windows have problems such as high energy consumption, slow response time, and poor stability. To solve these problems, a single‐step dual stabilization (SSDS) is newly proposed for t...

In article number 1906780, Kwang‐Un Jeong and co‐workers suggest a single‐step dual stabilization technique for fabricating smart windows. Upon irradiation with ultraviolet light with a photomask on the optical cell with photoisomerizable macrogelators and photopolymerizable monomers, liquid crystal physical gels and partition walls are simultaneou...

We report the fast response characteristics of flexible ultraviolet (UV) photosensors with GaN nanowires (NWs) and a graphene channel. The GaN NWs used as light-absorbing media are horizontally and randomly embedded in a graphene sandwich structure in which the number of bottom graphene layers is varied from zero to three and the top is a fixed sin...

Simultaneous manipulation of both transparency and luminescence is one of the biggest challenges in developing security materials and memory devices. To understand the crucial factors influencing such optical properties, we synthesized a new class of a transparent luminescent molecule (mPD) comprising dendritic alkyl chains as a model organic compo...

By controlling the hierarchical superstructures by chemical function transfer and shape amplification of molecular building blocks, advanced materials with the desired properties can be developed. To realize this concept, a latticework nanostructure is constructed for a single‐layered negative dispersion (ND) retarder by the newly synthesized hydro...

In article number 1905214, Ji‐Hoon Lee, Kwang‐Un Jeong, and co‐workers construct a latticework nanostructure for single‐layered coatable negative dispersion retarders by controlling the chemical function transfer and molecular shape amplification of programmed reactive mesogens. The single‐layered coatable negative retarder with an ideal value is s...

We reported an optical anisotropy conversion of a retarder film composed of rodlike and crosslike reactive molecules. We investigated the dependence of the optical anisotropy of the composite film on the relative ratio and the orientation of the constituent molecules. We used the rodlike molecule as a host and the crosslike molecule as a guest. We...

New hockey-stick-shaped liquid crystals (HSLCs) have been designed and synthesised. By extreme shortening of one ‘arm’ in the HSLCs, we have constructed the pronounced overall hockey-stick-shaped molecular conformation of these materials, and called the pseudo-rod-like (PRL) molecules with hockey-stick-shaped mesogen. The chemical structures were i...

Wearable technology offers new ways to be more proactive about our health and surroundings in real time. For next-generation wearable systems, robust storage or recording media are required to monitor and process the essential electrical signals generated under various unpredictable strain conditions. Here, we report the first fibriform organic tra...

For the construction of well-defined hierarchical superstructures of pristine [60]fullerene (C60) arrays, pyrene-based molecular tweezers (PT) were used as host molecules for catching and arranging C60 guest molecules. The formation of host-guest complexes was systematically studied in solution as well as in solid state. Two-dimensional proton nucl...

This work is aimed to fabricate ultra-thin coatable polarizers on a single substrate based on “host-guest” effect between highly ordered smectic reactive mesogen (RM) and dichroic dye. We designed and synthesized a new tolane-based RM with a highly ordered smectic A phase at room temperature. Polymerizable “host-guest” mixture was formulated from t...

Group III-nitride light-emitting diodes (LEDs) fabricated on sapphire substrates typically suffer from insufficient heat dissipation, largely due to the low thermal conductivities (TCs) of their epitaxial layers and substrates. In the current work, we significantly improved the heat dissipation characteristics of an InGaN/GaN-quantum-well (QW) gree...

Antireflective films for flexible display devices should be made by a coating process rather than a stretching process. Additionally, the compensator, which is the core of the antireflective film, must exhibit a wavelength-independent phase retardation in the visible light region in order to act as an ideal retarder. To satisfy all of these require...

Stimuli-responsive soft matters have been recognised by many scientists and engineers as very important because of their inherent characteristics in response to environmental changes. In particular, there has been much progress over the last few years on light-responsive soft matters that can respond remotely. By controlling the packing behaviours...

There has been considerable interest in nanomaterials for the development of anisotropic molecular alignment layers for electronic and biomedical applications. This review covers the recent progresses in the design, synthesis, and characterization of the automatic liquid crystal (LC) alignment layer. Amphiphilic hybrid nanomaterials consisting of o...

We synthesized a new liquid crystal (LC) dopant 4-[7-(4′-Cyanobiphenyl-4-yl)hexyloxy]bezoic acid (CBO7OBA) which can form dimers by hydrogen-bonding. We mixed the hydrogen-bondable CBO7OBA dopants with commercial nematic liquid crystal (NLC) mixtures and investigated the change of the flexoelastic ratio of the mixture. The flexoelastic ratio of the...

A short pitch cholesteric liquid crystal (CLC) acts as one-dimensional photonic crystals. It was widely studied for electro-optical switching devices. Although it was proposed for a switchable smart window, its spectral characteristics have critical limitations for window applications. In this report, we present dichroic-dye-doped short pitch CLC f...

To realize light-responsible phase chirality from achiral macrogelator in solid state, disc-shaped achiral macrogelator (B1AZ) was newly synthesized. B1AZ was self-assembled into a lamello-columnar structure in the bulk state, while single-handed helical fibrils (HF) with 400 nm of helical pitch were constructed by side-by-side lateral association...

Organic materials with linearly polarized luminescence (LPL) properties and good processability are critical to the development of advanced optical devices. To fabricate polymer-stabilized thin films with LPL properties, dicyanodistyrylbenzene-based reactive luminogens (abbreviated as DRL) containing both vinyl and thiol units were newly synthesize...

A series of dicationic imidazolium bis(tetrafluoroborate) salts were newly synthesized, and their phase transition behaviors were correlated with thermal, scattering, optical and conductivity results. The bis-imidazolium salts having side-chain lengths of C6-C10 showed plastic crystal mesophases, while a liquid crystal mesophase was formed in the b...

To address tremendous needs for developing efficiently heat dissipating materials with lightweights, a series of liquid crystalline epoxy resins (LCEs) are designed and synthesized as thermally conductive matrix. All prepared LCEs possess epoxies at the molecular side positions and cyanobiphenyl mesogenic end groups. Based on several experimental r...

In article number 1803291, Kwang‐Un Jeong and co‐workers show that hierarchical hybrid nanostructures are constructed by the host‐guest complex between the fullerene dendron and pyrene dendron. Based on the consideration of structural motifs and host‐guest interactions, fullerene and pyrene building blocks are successfully programmed and self‐assem...

Liquid crystals: painting a path to flexible mirrors An innovative paint containing polymer-stabilized liquid crystals can be turned into bendable and highly reflective mirrors. The brilliant hues found on peacock feathers arise from structural coloration, a phenomenon where tiny microstructures deflect and modify light waves. Kwang-Un Jeong at Cho...

Cu(In, Ga) Se2 (CIGS) thin-film solar cells are currently the fastest growing photovoltaic technology due to the higher performance ratio and lower energy payback time compared to the silicon, and good stability. Despite of these interesting properties, CIGS solar cells suffer from poor spectral response at short wavelengths particularly in the ran...

A photoresponsive chiral molecular crystal (abbreviated as PCMC) was programmed and synthezied by locating a chiral isosorbide at the core between two amphiphilic azobenzene building blocks. Owing to the bent shaped geometry, the PCMC itself can be organized into helical nanoribbons with a highly ordered smectic domain. Since the PCMC had not only...

In this study, we report highly efficient and flexible photosensors with GaN nanowires (NWs) horizontally embedded in a graphene sandwich structure fabricated on polyethylene terephthalate (PET). GaN NWs and the graphene sandwich structure are used as light-absorbing media and the channel for carrier movement, respectively. To form uniform high-qua...

The construction of fullerene (C60) hierarchical nanostructures with the help of amphiphilic molecules remains a challenging task in nanoscience and nanotechnology. Utilizing the host–guest complex concept, sub‐10 nm layered superstructures are constructed from a monofunctionalized C60 dendron (C60D, guest) and tweezer‐like pyrene dendron (PD, host...

For the development of anisotropic thermal interface materials (TIMs), a rod-shaped reactive monomer PNP-6MA is newly designed and successfully synthesized. PNP-6MA reveals a smectic A (SmA) mesophase between crystalline (K) and isotropic (I) phases. PNP-6MA can be oriented under a magnetic field (B = 2 T), and its macroscopic orientation can be ro...

The current study concerns about the large band gap of TiO2 for its use as photocatalysts. The photocatalytic activity of core-shell structured [email protected]2 nanoparticles were enhanced by the doping of nitrogen. The nitrogen doping has been done by simple hydrothermal method taking ethylenediamine as the precursor for nitrogen. The crystals s...

Pyrene‐based asymmetric liquid crystal dendron (PD) was newly synthesized for understanding the correlation of the kinetically controlled hierarchical superstructure with its properties. Owing to the competition bewteen driving forces, PD formed stable or metastable crystalline phases depending on the cooling rate. Various techniques were utilized...

To understand the relationship between kinetically controlled hierarchical superstructures and photophysical properties, pyrene‐based asymmetric liquid crystal (LC) dendrons (abbreviated as PD) were newly synthesized by covalently attaching a pyrene moiety (P) at a biphenyl‐based LC dendritic group (D). The phase transition behavior of PD has been...

Vulcanizates of chlorobutyl rubber (CIIR) with the accelerated sulfur generally exhibit poor crosslinking density owing to the low level of unsaturation in the backbone of CIIR. Therefore, the sulfur cured CIIR shows inferior thermo-mechanical properties at elevated temperature. In addition to this, the vulcanization of CIIR with accelerated sulfur...

This paper reports the formation of GaN and InN quantum dots (QDs) with symmetric spherical shapes, grown on SiN/Si(111). Spherical QDs are grown by modulating initial growth behavior via gallium and indium droplets functioning as nucleation sites for QDs. Field-emission scanning electron microscope (FE-SEM) images show that GaN and InN QDs are for...

Homopolymers with side-chain liquid crystalline (LC) units were prepared by RAFT polymerization of a new LC monomer, N-(4-dodecylphenyl)-4′-vinylbenzamide. The resulting polymers had low polydispersity, Mw/Mn < 1.2. Optical and thermal investigations confirmed that both the monomer and homopolymers have smectic structures. New diblock copolymers (B...

To develop light-triggered wringing gels, an asymmetric macrogelator (1AZ3BP) was newly synthesized by the chemically bridging a photoisomerizable azobenzene (1AZ) molecular machine and a biphenyl-based (3BP) dendron with a 1,4-phenylenediformamide connector. 1AZ3BP was self-assembled into a layered superstructure in the bulk state, but 1AZ3BP form...

We investigated the dependence of the dispersion of retardation on the UV-polymerization temperature and the molecular orientation in a self-organized smectic host-guest reactive mesogen (RM) compound. The positive dispersion of retardation was converted to the negative dispersion of retardation with decreasing the UV-polymerization temperature. Fr...