KR20220104525A - Chiral nanoporous template and method of manufacturing for them - Google Patents

Abstract

A manufacturing method based on a bottom-up template for manufacturing a chiral nanoporous template for providing a chiral environment for nematic liquid crystals is provided. The chiral nanoporous template of the present invention can be applied to applications such as chirooptic modulators and switches, and biological sensors.

Description

Chiral nanoporous template and manufacturing method thereof

The present invention relates to a chiral nanoporous template and a method for preparing the same, and more particularly, to a template prepared with a chiral material by a physical method without a chemical method by filling a non-chiral material.

Chirality is abundant in nature and plays a significant role in the origins of biological systems. Chirality has been studied extensively in the fields of chemistry, physics, biology, pharmacy and medicine. In general, helical aggregates (or chiral superstructures) are formed from chiral molecules. As an example, proteins and deoxyribonucleic acids (DNA) are helical aggregates and cause the formation of chiral superlattice structures from chiral molecules in fluids as well as solid states.

On the other hand, macroscopic spontaneous chiral segregation in achiral bent-core (BC) liquid crystal (LC) molecules was first reported in 1997 for the first time. The study of chirality in non-chiral LC molecules has been one of the most interesting topics not only in the field of LC but also in a wide range of materials science. One of these macroscopic chiral phases, the helical nanofilament (HNF) phase (also called the B4 phase), is the lowest-temperature mesophase of many BC-LCs. ), and was found to have a helical superlattice structure even though it is composed only of achiral molecules. Subsequent studies have suggested that the HNF phase is not LC, but rather semicrystalline, but the problem of breaking the chiral symmetry of the HNF phase is a serious problem for many chemists and physicists. influenced

Recently, attempts have been made to create chirooptic materials using binary systems of BC-type nematic (N) LC and rod-like nematic (N) LC. It has been shown that nanoscale phase separation occurs in this mixed system between the semi-crystalline HNF phase and the nematic liquid crystal (N-LC) phase. Experimental results of previous studies show that the structural chirality of the HNF phase affects the structure of the separated rod-like N-LC phase, and the self-assembled chiral superlattice related to the chirality of the HNF phase. form a structure

Therefore, there is a chirooptic effect in the non-chiral N-LC, the chirality of the binary mixture is modified, and the intensity of the chirality is amplified. An interesting approach based on this phenomenon has recently been reported. Circularly polarized luminescence (CPL) was observed in the achiral mixture of rod-shaped guest molecules and BC host molecules mixed with fluorescent dyes. These CPLs are clear evidence that N-LC molecules isolated from HNFs form chiral nanospaces (ie, chiral superlattice structures).

Republic of Korea Patent No. 1825597

The present invention aims to realize a chiral polymeric material by transferring chirality (or chiral information) from an HNF phase to a non-chiral molecule.

That is, the chiral nanospace separated from the HNF is fixed using a polymer stabilizer, and the polymer-stabilized chiral nanospace is used as a useful template to provide chirooptic effects.

In order to achieve the object to be solved, a chiral nanoporous template according to an aspect of the present invention includes a polymer network structure composed of a reactive mesogenic compound; and a plurality of nanopores formed on the polymer network structure.

The reactive mesogenic compound may be composed of a nematic liquid crystal (N-LC) and a reactive monomer, and the nematic liquid crystal (N-LC) may be 4-cyano-4'-pentylbiphenyl, and the reactive monomer is 2 -methyl-1,4-phenylene bis(4-(((4-(acryloyl oxy)butoxy)carbonyl)oxy)benzoate).

The chiral nanoporous template may have an inverse helical nanofilament structure.

In addition, the method for preparing a chiral nanoporous template according to an aspect of the present invention comprises the steps of: preparing a precursor mixture including a bent nuclear molecule, a reactive mesogenic compound, and a photoinitiator; preparing a template by photocuring the precursor mixture; removing the bent nuclear molecule on the template; and drying the template.

The bent nuclear molecule may have a helical nanofilament phase as a nanofission phase, and the bent nuclear molecule is 1,3-phenylene bis[4-(4-eptyloxyphenyliminomethyl)-benzoate ] can be.

The reactive mesogenic compound may be composed of a nematic liquid crystal (N-LC) and a reactive monomer, and the nematic liquid crystal (N-LC) may be 4-cyano-4'-pentylbiphenyl, and the reactive monomer is 2 -methyl-1,4-phenylene bis(4-(((4-(acryloyl oxy)butoxy)carbonyl)oxy)benzoate).

The photoinitiator may be DMPAP (2,2-dimethoxy-2-phenylacetophenone).

The photocuring may be performed at 80 to 120 °C.

The removal of the bent nuclear molecule may be performed using 1,2-dichlorobenzene.

According to one aspect of the present invention, there is provided a bottom-up-based template manufacturing method for manufacturing a chiral nanoporous template that provides a chiral environment.

In addition, the present invention can prepare a chiral nanoporous template from a non-chiral material (molecule) without a complicated manufacturing process through the bottom-up self-assembly method.

In addition, the present invention can provide a chiral nanoporous template for applications such as chirooptic modulators and switches, and biological sensors.

1A is a flowchart of a method for manufacturing a chiral nanoporous template according to an embodiment of the present invention.
Figure 1b shows a schematic diagram of a manufacturing process of a chiral nanoporous template according to an embodiment of the present invention.
2 is a diagram showing an SEM image and a schematic diagram of each cross-section in the manufacturing process of a chiral nanoporous template according to an embodiment of the present invention.
Figure 3a shows a typical polarized light microscopy (POM) image of the film at each step of the manufacturing process of the chiral nanoporous template at room temperature (RT) according to an embodiment of the present invention.
3b to 3d show three different LC materials (8CB (Sigma-Aldrich), BYLC 53XX (BaYi) Space Co.) and MLC-7029 (Merck)) show a polarization optical microscope (POM) image of the chiral nanoporous template when refilled in stage 3 (see Fig. 1b).
Figure 4a shows a typical CD spectrum measured for single domains (monodomains) in each step of the manufacturing process of the chiral nanoporous template at room temperature (RT) according to an embodiment of the present invention.
FIG. 4b shows CD spectra rotated at various azimuth angles (α=0, 30, 60, and 90°) after refilling with a non-chiral compound in a chiral nanoporous template according to an embodiment of the present invention.
Figure 5 shows 2 in the N phase (at room temperature (RT) and Iso phase (at 120 ° C)) after refilling the achiral compound in the chiral nanoporous template according to an embodiment of the present invention; The CD spectra for the enantiomer domains (Fig. 5(a)) and the CD spectra for the two enantiomers under various electric field conditions at room temperature (RT) (Fig. 5(b)) are shown.
6 is a pyrromethene-based fluorescent dye (PM580) doped with non-chiral N-LC to further demonstrate the functionality of the chiral nanoporous template according to an embodiment of the present invention. A schematic diagram (FIG. 6 (a)) and circular intensity difference I _left - I _right (FIG. 6 (b)) are shown.
7 (a) is a chiral nanoporous template according to an embodiment of the present invention, each of the chiral domains corresponding to the N phase (phase) and the Iso phase (phase) refilled with a non-chiral compound | I _left - I _right | The spectrum is shown, and FIG. 7 (b) is the domain of the domain under various electric field conditions at room temperature (RT) refilled with a chiral compound in a chiral nanoporous template according to an embodiment of the present invention. I _left - I _right | spectrum is shown.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings and contents described in the accompanying drawings, but the present invention is not limited or limited by the embodiments.

The terminology used herein is for the purpose of describing the embodiments and is not intended to limit the present invention. In this specification, the singular also includes the plural, unless specifically stated otherwise in the phrase. As used herein, “comprises” and/or “comprising” refers to the presence of one or more other components, steps, operations and/or elements mentioned. or addition is not excluded.

As used herein, “embodiment”, “example”, “aspect”, “exemplary”, etc. are to be construed as advantageous in any aspect or design described as being preferred or advantageous over other aspects or designs. is not doing

The terms used in the description below are selected as general and universal in the related technical field, but there may be other terms depending on the development and/or change of technology, customs, preferences of technicians, and the like. Therefore, the terms used in the description below should not be understood as limiting the technical idea, but should be understood as exemplary terms for describing the embodiments.

In addition, in certain cases, there are also terms arbitrarily selected by the applicant, and in this case, the meaning will be described in detail in the corresponding description. Therefore, the terms used in the description below should be understood based on the meaning of the term and the content throughout the specification, not the simple name of the term.

Meanwhile, terms such as first and second may be used to describe various components, but the components are not limited by the terms. The terms are used only for the purpose of distinguishing one component from another.

In addition, when a part such as a film, layer, region, configuration request, etc. is said to be “on” or “on” another part, it is not only when it is directly on the other part, but also another film, layer, region, or component in the middle. Including cases where etc. are interposed.

Unless otherwise defined, all terms (including technical and scientific terms) used herein may be used with the meaning commonly understood by those of ordinary skill in the art to which the present invention belongs. In addition, terms defined in a commonly used dictionary are not to be interpreted ideally or excessively unless clearly defined in particular.

Meanwhile, in describing the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted. In addition, the terms used in this specification are terms used to properly express an embodiment of the present invention, which may vary according to the intention of a user or operator or a custom in the field to which the present invention belongs. Accordingly, definitions of these terms should be made based on the content throughout this specification.

A polymer network structure composed of a reactive mesogen compound (RMC) according to an embodiment of the present invention; and a plurality of nanopores formed on the polymer network structure.

The reactive mesogenic compound may be a photoreactive nematic liquid crystal (N-LC) compound, and the reactive mesogenic compound may include a nematic liquid crystal (N-LC) and a reactive monomer.

The nematic liquid crystal (N-LC) may be a rod-like nematic liquid crystal (N-LC) compound, and the nematic liquid crystal (N-LC) may be 4-cyano-4'-pentylbiphenyl (5CB). ), 4-n-octyl-4'-cyanobiphenyl (8CB), BYLC53XX (from BaYi Space Co.) or MLC-7029 (from Merck).

The reactive monomer may be 2-methyl-1,4-phenylene bis(4-(((4-(acryloyl oxy)butoxy)carbonyl)oxy)benzoate).

The chiral nanoporous template may have an inverse helical nanofilament structure.

1A is a flowchart of a method for manufacturing a chiral nanoporous template according to an embodiment of the present invention.

Referring to FIG. 1A , the method for preparing a chiral nanoporous template according to an embodiment of the present invention prepares a precursor mixture including a bent-core (Bent-Core; BC) molecule, a reactive mesogenic compound (RMC), and a photoinitiator step (S110); preparing a template by photo-curing the precursor mixture (S120); removing the bent nuclear molecule on the template (S130); and drying the template (S140).

S110 is a step of preparing a precursor mixture as a material for preparing a template through photocuring, wherein the precursor mixture includes a bent nucleus (BC) molecule, a reactive mesogenic compound (RMC) and a photoinitiator, and more specifically, a bent nucleus It is based on a binary mixture of a molecule and a reactive mesogenic compound, and may include a small amount of a photoinitiator in the binary mixture.

The bent nuclear molecule may have a helical nanofilament phase (B4 phase) as a nanofission phase, and the bent nuclear molecule is 1,3-phenylene bis[4-(4-eptyloxyphenyliminomethyl)- benzoate]. The helical nanofilamental network of the bent-nuclear molecule was utilized as a three-dimensional template, and thus the final product, a chiral nanoporous template, is an inverse helical nanofilament (or 'inverse nanohelical') structure. structure) is included.

The reactive mesogenic compound may be a photoreactive nematic liquid crystal (N-LC) compound, and the reactive mesogenic compound may include a nematic liquid crystal (N-LC) and a reactive monomer.

The nematic liquid crystal (N-LC) may be a rod-like nematic liquid crystal (N-LC) compound, and the nematic liquid crystal (N-LC) may be 4-cyano-4'-pentylbiphenyl (5CB). ), 4-n-octyl-4'-cyanobiphenyl (8CB), BYLC53XX (from BaYi Space Co.) or MLC-7029 (from Merck).

The reactive monomer may be 2-methyl-1,4-phenylene bis(4-(((4-(acryloyl oxy)butoxy)carbonyl)oxy)benzoate).

The photoinitiator may be DMPAP (2,2-dimethoxy-2-phenylacetophenone).

The photoinitiator may be included in an amount of 0.5 to 1 wt% in the precursor mixture.

S120 is a step for preparing a template from the precursor mixture, and may be to form a template through photocuring treatment using UV light with respect to the precursor mixture, and the template may be in the form of a film.

In S120, the precursor mixture may be filled in a cell composed of an upper plate and a lower plate glass to perform photocuring, and the distance between the upper plate glass and the lower plate glass of the cell may be 1 to 10 μm.

The photocuring treatment temperature in S120 may be performed in a temperature range at which phase separation of the precursor mixture is implemented, and more specifically, the photocuring may be performed at 80 to 120 °C, preferably It may be carried out at 100 °C. The temperature range of the photocuring is 80 to 120 ℃, more preferably 100 ℃, as the temperature range of <HNF / N> of the nanofission phase of the precursor mixture is confirmed at 80 to 120 ℃, the photocuring is performed at 100 ℃ .

S130 is a step of removing the unpolymerized material present on the photo-cured template, and more specifically, a step of removing the bent nuclear molecules that do not participate in the photopolymerization reaction during the manufacturing process of the template.

The bent nuclear molecule does not participate in the photopolymerization reaction on the template, and occupies a certain space (nanospcace) on the template. By removing the bent nuclear molecule, the polymer network on the template is passed through the space occupied by the bent nuclear molecule. Network) as a nanopore (nanopore) is formed.

The bent nuclear molecule undergoes a phase change to the HNF phase during the photopolymerization process, and the nanopore formed by removing the bent nuclear molecule has an inverse HNF structure, which is derived from a chiral supramolecular structure that is HNF. A novel chiral supramolecular structure (polymer network) is formed.

The removal of the bent nuclear molecule may be performed using an organic solvent that dissolves the bent nuclear molecule, and the organic solvent may be 1,2-dichlorobenzene.

S140 is a step of providing a final product, a chiral nanoporous template, by drying the template from which the bent nuclear molecules are removed. In this case, the provided chiral nanoporous template may be in the form of a nanoporous film.

More specifically, S140 may be removed by completely evaporating the residual solvent by drying at room temperature (25° C.) for 24 hours (h).

More specifically, in the case of the manufacturing method of the chiral nanoporous template of the present invention,

Nano-isolated rod-like N-LCs were synthesized as photopolymerizable reactive mesogen and photopolymerized with BC molecules. After photopolymerization, BC molecules in the HNF phase were removed from the prepared template, so that only a polymer network with “inverse HNF” remains on the template. Nanoporous films (nanoporous templates) with such an inverse HNF structure have the ability to memorize and transmit chirality, which may be useful for chirooptic applications. When the inverted HNF structure of this nanoporous template was filled with achiral N-LC, a clear and strong circular dichroism (CD) appeared. Due to the stimuli-responsive nature of packed N-LCs, the CD signal can be easily modulated by applying an electric field or heat. This is according to the "washout-refill method" and is intended to implement a photonic crystal structure based on a stimuli-tunable polymer templated from cholesteric LC or bluephase LC.

In addition, CPL can be implemented by filling the inverted HNF structure on the nanoporous template with achiral N-LC doped with a fluorescent dye. The CPL intensity may be modulated by an external stimulus similar to the CD signal. Such chirooptic properties were realized in a system composed only of non-chiral molecules. In addition, a chiral template obtained from a non-chiral molecule through a bottom-up self-assembly methodology does not require a complicated manufacturing process.

Hereinafter, the present invention will be described in more detail through examples. These Examples are for explaining the present invention in more detail, and the scope of the present invention is not limited by these Examples.

ready yes. Chirality Nanoporous Template Synthetic Materials

The mixture used for the preparation of the template in the present invention is a BC (bent-core) molecule (P7: 1,3-phenylene bis[4-(4-eptyloxyphenyliminomethyl)-benzoate]) and a reactive mesogen compound; RMC).

BC molecule (P7) is a method according to Kumazawa et al. (Important Role Played by Interlayer Steric Interactions for the Emergence of the Ferroelectric Phase in Bent-Core Mesogens. J. Mater. Chem. 2004, 14, 157-164.) synthesized

RMC is a nematic liquid crystal (N-LC) (5CB: 4-cyano-4'-pentylbipenyl) and a reactive monomer (LC242: 2-methyl-1,4-phenylene bis (4-(((4- (acryloyl oxy) butoxy)carbonyl)oxy)benzoate)).

The mixture further comprises a photoinitiator (DMPAP: 2,2-dimethoxy-2-phenylacetophenone).

LC242 was purchased from BASF and 5CB and DMPAP were purchased from Sigma-Aldrich.

The mixing ratio of the mixture in the present invention is shown in Table 1 below.

mixture P7 RMC
(LC242:5CB=67 wt%:33 wt%) DMPAP Mixing ratio (wt%) 49.5 49.5 One

P7 and RMC were dissolved together in chloroform and mixed through sonication. Then, in order to remove the solvent (chloroform), it was dried by heating. Upon cooling, the order of the phases of neat P7 and RMC is Iso-(170 °C)-B2-(154 °C)-B7-(144 °C)-HNF(helical nanofilament) and Iso-(120 °C)-N-, respectively (80 °C)-Cryst.

To fill the nanopores of the template, N-LC (HTW109100-100, HCCH) of an achiral mixture was used. The order of the phases upon cooling was Iso-(120 °C)-N-(-40 °C)-Cryst. In addition, three other LC materials (8CB (Sigma-Aldrich), BYLC 53XX (BaYi Space Co.) and MLC-7029 (Merck)) were filled into the nanoporous film. Among them, MLC-7029 has negative dielectric anisotropy.

The emissive N-LC mixture for the CPL (Circular Polarizer) experiment was a pyrromethene-based fluorescent dye (PM580: [[(4-butyl-3) having an emission peak at 560 to 580 nm). ,5-dimethyl-1H-pyrrol-2-yl)(4-butyl-3,5-dimethyl-2H-pyrrol-2-ylidene)methyl]-methane](difluoroborane)) was doped at 0.5 wt%. PM580 was purchased from Exciton.

The chemical structural formula of P7 may be represented by the following formula (1).

[Formula 1]

The chemical structural formula of LC242 may be represented by the following formula (2).

[Formula 2]

The chemical structural formula of 5CB may be represented by the following formula (3).

[Formula 3]

The chemical structural formula of PM580 may be represented by Chemical Formula 4 below.

[Formula 4]

manufacturing example. Preparation of Chiral Nanoporous Template

A binary mixture is prepared by mixing BC molecules (P7) and RMC (CB5 + LC242) of the preparation example, at this time, by adding DMPAP as a photoinitiator to the binary mixture to prepare a precursor mixture, The mixing ratio of the precursor mixture is the same as the mixing ratio of Table 1 above. P7 and RMC (CB5 + LC242) were dissolved together in chloroform and mixed by sonication. Then, in order to remove the solvent (chloroform), it was dried by heating.

The sequence of the nanosegregated phases of the binary mixture in the precursor mixture prior to photocuring is Iso-(140°C)-<HNF/Iso>-(120°C)-<HNF/N>-( 80° C.)-<HNF/Cryst>. To describe the nanosegregated phases of a binary mixture consisting of P7 and RMC, the notation of a binary mixture consisting of P7 and RMC is <phase of P7(BC molecule)/phase of RMC(rod-) like molecule)>, for example, <HNF/N> indicates that P7 is located in HNF phase, whereas RMC is located in N phase.

An LC (liquid crystal) cell with a gap of 2 μm is fabricated with two parallel slide quartz substrates without surface treatment, and the LC cell is not absorbed in the near-ultraviolet (UV) region. and there is no fluorescence.

The LC cell fills the precursor mixture containing P7 and RMC. The binary mixture charged in the LC cell (sample) was irradiated with UV light of a low pressure mercury lamp (254 nm, 30 mW/cm ² ) at 100° C. for 10 minutes (min). Then, photocuring is performed to produce a template. As the temperature range of <HNF/N> of the nanofission phase of the binary mixture in the precursor mixture was confirmed at 80 to 120 °C, photocuring was performed at 100 °C.

Photocured template to remove P7 and residual unpolymerized RMC by immersing the LC cell in 1,2-dichlorobenzene (purity 99%) at 150 °C for 24 h (h). was washed. At this time, the organic solvent 1,2-dichlorobenzene (purity 99%) was used for high boiling point temperature and selective dissolvability of BC molecules (P7), The fused structure can withstand temperatures up to 150 °C.

Thereafter, the residual solvent of the LC cell was completely evaporated by drying at room temperature (25° C.) for 24 hours (h).

measurement example. Observation with Ultra High Resolution Field Emission Scanning Electron Microscope (UHR-FE-SEM)

UHR FE-SEM (S-5500, Hitachi) observation was performed to confirm the nanoscopic morphology of the chiral nanoporous template before and after removal of HNF. After disassembling the sample LC cell to check the internal structure of the sample, a thin (~5 nm) layer of osmium was sputtered on the exposed surface.

measurement example. Polarized optical microscopy (POM) observation

POM analysis was performed using a polarized optical microscope (OPTIPHOT-POL, Nikon), and images were recorded in transmission mode using a camera with two linear polarizers.

measurement example. Measurement of Circular Dichroism (CD)

The solid CD spectra were obtained using a microspot CD device built into a J-720WI spectropolarimeter (Jasco) to obtain chiral domains at different electric field intensities and temperatures. (chiral domains) were collected. To measure the CD signal in the small chiral domain, focal-reducing optics were installed in the CD spectrometer. A typical beam diameter is smaller than the chiral domain, less than 10 μm. The thickness of the quartz LC cell used for CD measurement is less than 2 μm.

measurement example. Measurement of circularly polarized light (CPL)

A custom instrument was installed for CPL measurements using monodomains. The non-polar white light of the LDLS system (EQ-99X, Energyq) was used. Light was intensively focused on a sample after being monochromated using a band-pass filter (525 nm). The polarization of the emission output was modulated using a photoelastic modulator (PEM) (PEM-100 I/FS50, HINDS) oscillating at a frequency of about 50 kHz. The modulated polarized signal was converted into an intensity-modulated signal using a linear polarizer and then sensed as a modulated current by a photomultiplier tube (PMT) (H6780, Hamamatsu).

Then, the 1f alternating current (AC) component of the modulated signal was analyzed using a lock-in amplifier 7265 (signal recovery) using the reference frequency of the PEM. Circular differences ( I _left - I _right ) and ( I _left + I _right ) were inferred from the AC and DC components of the modulated signal, respectively. Spectral CPL was measured using an n-line Fastie-Ebert monochromator (Edmund Optics) set up just before PMT.

experimental example.

Synthesis of Chiral Compounds Using Chiral Nanoporous Templates

In order to specify the measurement steps in various experimental examples to be described later, the preparation process of the chiral nanoporous template in the above-described preparation example and the process of filling the achiral compound to prepare the chiral compound in the prepared template It is summarized below with reference to FIG. 1B.

Referring to FIG. 1B , a small amount of a photoinitiator was added to a binary mixture of a BC (Bent-Core) molecule (P7) and a photoreactive N-LC compound (RMC). The mixture is introduced into an LC cell composed of two parallel slides of quartz, wherein the LC cell does not absorb in the near-ultraviolet (UV) region and does not emit fluorescence. .

RMC is composed of rod-like photoreactive mesogen (LC242, 50 wt %) and nematogen (5CB, 50 wt %). Pure LC242 was very viscous and did not separate from the HNF phase at all, so it was diluted with 5CB.

UV light over the temperature range (80 ~ 120 °C) (BC is HNF phase, RMC is N phase) at which the nano- seggregation of the bicomponent mixture filled in the LC cell occurs. A template is prepared through photocuring using This procedure is referred to as stage 1 (see Fig. 1b).

Then, the template was immersed in an organic solvent (1,2-dichlorobenzene) at an increased temperature of 150 °C to dissolve the BC molecules and residual unpolymerized RMC. Thereafter, the residual solvent was removed at room temperature (RT) (stage 2 (see FIG. 1b )).

Finally, the template is refilled with another commercially available achiral helical N-LC (HTW109100-100, HCH) at room temperature (RT) to prepare the chiral compound (stage 3 (Fig. see 1b)).

measurement example. Observation with Ultra High Resolution Field Emission Scanning Electron Microscope (UHR-FE-SEM)

Ultrahigh-resolution field-emission scanning electron microscopy (UHR FE-SEM) was used to observe the morphologies of the photocured chiral nanoporous template (Preparation Example). The cross section of the chiral nanoporous template prepared in Preparation Example was observed.

Figure 2 (a) shows BC molecules (HNF phase) before removal (stage 1, see Fig. 1b), and Fig. 2 (b) shows BC molecules (HNF phase) after removal (stage 2, see Fig. 1b). The UHR FE-SEM image of

Referring to (a) of FIG. 2 , in stage 1, because the BC molecules (HNF phase) and the photocured synthetic polymer coexisted in the space within the template, they appeared almost homogeneous and flat.

On the other hand, referring to FIG. 2(b), in stage 2, nano-pores are clearly observed in the micrograph. Through this, BC molecules (HNF phase) on the chiral nanoporous template )) was removed through washing, and only the template polymer network remains due to the removal of BC molecules. Although the polymer wall appeared to be slightly eroded, warped walls were observed in some places, indicating the formation of an inverted HNF structure. The estimated half-pitch of this inverse helix is ˜100 nm, which can be compared to a typical HNF phase. The nanopore size was estimated to be tens to hundreds of nanometers in diameter in the interstices in the polymer network, which is also consistent with the general diameter of the HNF phase of the BC system.

Therefore, the morphological chirality of the chiral nanoporous template is copied from the original HNF network in stage 2 as shown in FIG. 2(c) and transferred to the polymer (RMC) constituting the chiral nanoporous template. it can be seen that

measurement example. Polarized optical microscopy (POM) observation

Figure 3a shows a polarization optical microscope (POM) image at room temperature (RT) of the chiral nanoporous template in stage 1, stage 2, and stage 3 (see Figure 1b) of the manufacturing process of the chiral nanoporous template.

Referring to Figure 3a, the two different regions in stage 1 can be clearly distinguished by slightly crossing the polarizers, whereas the very low birefringence for the crossed-Nicols condition is very high. got dark vision. The ratio of occurrence of these two regions was about 50:50.

This indicates that the two optically active regions are two enantiomeric domains with opposing chirality.

Since achiral BC molecules are known to exhibit unavoidable chirality degeneracy (i.e., optical segregation) through spontaneous symmetry penetrating in-layer tilt, the Chirality is considered to be related to the handedness of the initially formed HNF nuclei during the separation process.

At stage 2, the two chiral domains are almost indistinguishable under the POM. Since the absorption band of the photocured synthetic polymer is much shorter than the visible wavelengths, the optical rotation of the visible region is too small to be recognized by the naked eye.

However, in stage 3, two enantiomeric regions were reproduced with the same signs of optical activity as in stage 1. The chirooptical properties in stage 3 are due to the pores being filled with N-LC. Thus, the chirality is transferred from the inverted HNF to the packed N-LC, that is, the photocured synthetic polymer film with the nanoporous inverted HNF structure has the chirality transferred to another achiral medium. It can serve as a chiral template that can be used to deliver. This trend was consistently observed when the nanoporous film was refilled with N-LC materials regardless of whether positive dielectric anisotropy or negative dielectric anisotropy was present.

In this regard, additionally, three different LC materials (8CB (Sigma-Aldrich), BYLC 53XX (BaYi Space Co.) and MLC-7029 (Merck)) were used to refill stage 3 (see Fig. 1b). Polarized optical microscopy (POM) images of the chiral nanoporous template are shown in Fig. 3b (8CB), Fig. 3c (BYLC 53XX), and Fig. 3d (MLC-7029), respectively.

experimental example. Measurement of Circular Dichroism (CD)

In order to more clearly observe chirooptical features, microscopic CD observation was performed. CD spectroscopy was performed to confirm the existence of a chiral superstructure. Therefore, it is only necessary to obtain relative information, not quantified information, from CD measurement. In particular, when a chiral superlattice structure is generated, a CD signal appears, and similarly, a CD signal does not appear when there is no chiral superlattice structure. FIG. 4a shows typical CD spectra measured at room temperature (RT) for monodomains in stage 1, stage 2, and stage 3 (see FIG. 1b).

Referring to FIG. 4A , in stage 1, mirror inversion related to two enantiomeric domains was confirmed in the CD spectrum. This CD signal is mainly due to BC molecules and N-LC molecules in HNF formation. This was confirmed by the disappearance of the CD signal in stage 2. On the other hand, a smaller, better-shaped CD signal (Fig. 4a inset) was observed in the range of 300 to 350 nm, which corresponds to the absorption wavelength of the photocured polymer. This confirms that the photocured polymer has the form of a chiral superlattice structure that generates a CD signal. That is, the structural chirality of the HNF phase was successfully transferred not only to the surface morphology of inverse HNF but also to the internal structure of the photocured polymer. That is, while chirality (or chiral information) was transferred from the nanoporous film to a specific non-chiral N-LC phase, not only the chirality was transferred but also the chirality was amplified. A slight rotation of the cell azimuthally alters the CD spectrum, eliminating the possibility of artifact signals due to birefringence.

In stage 3, the CD signal reappeared due to the chiral template effect of the chiral nanoporous film (chiral nanoporous template). In particular, the CD intensity of stage 3 tends to be significantly improved compared to the case of values with the same sign in stage 1. That is, the transfer of chirality (or chiral information) from the chiral nanoporous template to the non-chiral N-LC phase was further amplified as well.

Figure 4b shows the CD spectrum rotated at various azimuth angles (α=0, 30, 60, and 90°) in stage 3. Referring to FIG. 4B , if the sample (chiral nanoporous template) is rotated in an azimuth angle, the CD spectrum is changed, and artifact signals due to birefringence can be removed.

When the nanoporous film is refilled with N-LC molecules, the template polymer (reverse HNF, Fig. 2(c)) forms a network that acts as a porous nanoconfinement medium with a large internal area, The refilled N-LC molecules are trapped in nanoscale interstitial volumes between polymers. In the vicinity of template polymers, N-LC molecules can be affected by the polymer surface.

The chiral transfer from the nanoporous film to the refilled achiral N-LC molecules can be described as follows: the refilled N-LC molecules are aligned along the grooves of the template polymer network and the template polymer It can be seen that it is fixed to the templated polymer surfaces. When the N-LC molecules are parallel to each other and aligned perpendicular to the axis of the template polymer network, the N-LC molecules assemble into a helicoidal structure along the axis of the template polymer network. That is, the gradient direction of the N-LC molecules with respect to the axis of the template polymer network is formed around the axis of the template polymer network, thereby creating a chiral superlattice structure. It can be seen that this helical structure is similar to the slightly twisted N-LC structure rather than the helical structure of the conventional cholesteric LC.

In addition, the amplified CD signal after the N-LC molecules are refilled into the nanoporous film can be explained as follows: The chiral superlattice structure of the template polymer network is the chiral superlattice structure of the N-LC molecule in this case. It can be transferred directly to chirality. The CD signal is amplified because the chiral signals of the template polymer network (stemming from HNF phase) and superlattice structures (stemming from refilled N-LC molecules) are identical. This result can be easily predicted by the contribution of the long-range orientation order of the N-LC molecules. That is, the macroscopic chirality of the refilled nanoporous film can be amplified to bulk regions through a specified N-LC medium with a long-range orientation sequence apart from the polymer surface.

As described above, the stage 3 nanoporous film has two enantiomeric domains in the N-LC phase at room temperature (RT), and shows a distinct CD spectrum with mirror inversion. However, when the nanoporous film was heated to the temperature (120 °C) region of the isotropic (Iso) phase, the CD signal almost disappeared (Fig. 5(a)). It can be seen that long-range ordering of LCs plays an important role in CD signal induction. The CD signal was restored when the nanoporous film was cooled back to room temperature (RT), that is, the phase was converted to the N-LC phase. This is representative of a temperature-modulated chiroptic function.

Figure 5 (a) is the CD spectrum for two enantiomeric domains in the N phase (at room temperature (RT)) and the Iso phase (at 120 °C) in stage 3 (see Figure 1b). will show FIG. 5(b) shows CD spectra for two enantiomers under various electric field conditions at room temperature (RT) in stage 3 (see FIG. 1b ).

The POM image corresponding to two phases is shown in the inset of FIG. 5(b). While the two chiral domains can be clearly identified in the N phase using a slightly uncrossed polarizer, it is not easy to identify the domain boundaries in the Iso phase. These two chiral domains can be distinguished again after the Iso phase is cooled back to the N phase. These POM observations are consistent with CD measurement results.

Stimuli-responsive modulation is also performed by applying an electric field. Figure 5(b) shows typical CD spectra for two enantiomeric domains under various electric fields at room temperature (RT). In addition, as shown in the top inset of Fig. 5 (b), the CD intensity was indicated as a function of the applied electric field. This means that N-LC molecules immobilized on the polymer network can play an important role in the formation of chiral superlattice structures. The CD intensity was constant within a certain range, indicating that the refilled N-LC molecules were strongly immobilized on the surface of the template polymer network. Conversely, since the reorientation of N-LC molecules (in nanopores) decomposed the chiral superlattice structure, the CD intensity rapidly decreased as the electric field increased above the threshold value. Therefore, it can be seen that a kind of Freedericksz transition occurred in the N-LC. When the electric field was removed, the N-LC molecules of the nanopores reassembled into the initial chiral superlattice structure, restoring the CD-active state. This was again clearly confirmed by the POM observation (bottom inset of Fig. 5(b)), and a sufficiently strong electric field aligned the N-LC molecules (α > 0) parallel to the electric field, which Under the condition of crossed-Nicols, the birefringence decreases, which tends to further decrease the brightness. While the two enantiomeric domains can be clearly distinguished in the absence of an electric field, we observe a distinct textural change with uncrossed polarizers because the boundary of the enantiomeric domains gradually disappears with increasing electric field strength. can do. When a sufficiently strong electric field is applied, the enantiomeric domain boundaries become almost indistinguishable to the naked eye. When the applied electric field is removed, the two chiral domains (enantiomeric domains) are restored and this conversion process can be repeated. Typical modulation (applied electric field) and relaxation (after electric field removal) times are both about 10-20 ms. Since molecular dynamics occur in hundreds of nano-sized pores, rapid reactions can be observed.

experimental example. Measurement of circularly polarized light (CPL)

In order to further prove the functionality of the chiral nanoporous template (chiral nanoporous film) prepared in Preparation Example, it was re-doped with pyrromethene-based fluorescent dye (PM580) with achiral N-LC. CFL emissivity was investigated by filling (FIG. 6 (a)). When chirality is transferred to a fluorescent achiral N-LC to form a chiral superlattice structure, a CPL signal is generated. Fig. 6(b) shows a prototype excited using nonpolarized 525 nm light for two enantiomeric domains of a chiral nanoporous template filled with fluorescence N-LC (at RT). It shows the circular intensity difference, I _left - I _right . where I _left and I _right are the intensities of left- and right-handed circularly polarized emission, respectively. The CPL spectra obtained from the two enantiomeric domains are mirror images of each other. In addition, to quantify the CPL level, a luminescence dissymmetry factor g _lum defined as 2( I _left - I _right )/( I _left + I _right ) was used. For most small organic chiral molecules, the luminescence asymmetry constant is generally in the range of 10 ^-5 to 10 ^-3 . The estimated g _lum for this experiment was 2 Х 10 ^-3 to 3 Х 10 ^-3 for both domains (see Fig. 5(b), inset). The detected CPL originated from a chiral superlattice structure formed by fluorescence N-LC, so this result further confirms the transfer of chirality.

FIG. 7(a) shows each of the chiral domains corresponding to the N phase and the Iso phase in stage 3 (see FIG. 1b). I _left - I _right | The spectrum is shown, and (b) of FIG. 7 shows the domains under various electric field conditions at room temperature (RT) in stage 3 (see FIG. 1b ). I _left - I _right | spectrum is shown.

Fig. 7(a) is a typical || I _left - I _right | It shows a comparison of the spectra. Similar to the CD signal, the CPL signal almost disappeared when the nanoporous film was heated to the Iso phase region (120 °C). As expected, the CPL signal reappeared upon cooling to room temperature (RT), i.e., upon re-entering the N-LC phase. In addition, this confirms that the chiral superlattice structure formed by N-LC in the nanopores plays an important role in the induction of CPL signals. CD and CPL signals were inactivated in the cooled solid state from the N-LC phase. In the solid state, there exists not only long-distance directional ordering, but also positional ordering. The formation of chiral superlattice structures influenced by the grooves of the template polymer can be hampered by the intrinsic strong localization of the solid state. Therefore, the phenomenon observed in the present invention was not observed in the nanoporous film filled with solid-state molecules.

Modulation of the CPL signal by electric stimuli is also possible. As shown in Fig. 7(b), as the applied electric field increases, | I _left - I _right | decreased, because the chiral superlattice structure in the nanopores was continuously collapsed through the reorientation of N-LC molecules. When the electric field was removed, the LC molecules of the nanopores restored the superlattice structure to restore the initial CPL active state.

Finally, the advantages of the present invention compared to previous studies are as follows.

First, BC molecules and N molecules nanoseparated in the HNF phase tend to be further separated into macroscopic aggregates with the lapse of time, which leads to deterioration of chirooptic properties. However, the HNF network of the present invention is stabilized by photocross-linking of the N region, and further nanosegregation is suppressed.

Second, the active temperature range for stimuli-responsive chirooptic properties was broadened due to the use of LC molecules with a wide N temperature range including room temperature (RT), whereas the CPL in the previous study was 50 This was only possible at temperatures above °C.

Therefore, the photo-cross-linking method greatly improves the stability and reliability of the system, which was relatively poor in previous studies.

conclusion

A chiral nanoporous template with excellent functionality was fabricated based on spontaneous nanoscale-level segmentation in a non-chiral binary system of BC molecules and reactive mesogenic compounds. Scanning electron microscopy (SEM) confirmed the formation of an inverse nanohelical structure by photocrosslinking, which serves as a template for N-LC. These chiral nanotemplates are simply composed of achiral molecules and can be easily manufactured by a simple bottom-up methodology without a complicated manufacturing process. It has been demonstrated that these chiral nanoporous films can act as three-dimensional nanomolds that give rise to chirooptic properties, i.e., stimuli-responsive CD and CPL. This methodology can be used as a strategy to construct new chirooptic materials that can be applied to various applications including chirooptic modulators and switches, biological sensors, and the like.

On the other hand, the embodiments of the present invention disclosed in the present specification and drawings are merely presented as specific examples to aid understanding, and are not intended to limit the scope of the present invention. It will be apparent to those of ordinary skill in the art to which the present invention pertains that other modifications based on the technical spirit of the present invention can be implemented in addition to the embodiments disclosed herein.

Claims (14)

a polymer network structure composed of a reactive mesogenic compound; and
A chiral nanoporous template comprising a plurality of nanopores formed on the polymer network structure.
The method of claim 1,
The reactive mesogenic compound is a chiral nanoporous template, characterized in that it consists of a nematic liquid crystal (N-LC) and a reactive monomer.
3. The method of claim 2,
The nematic liquid crystal (N-LC) is a chiral nanoporous template, characterized in that 4-cyano-4'-pentylbiphenyl.
3. The method of claim 2,
The reactive monomer is 2-methyl-1,4-phenylene bis(4-(((4-(acryloyl oxy)butoxy)carbonyl)oxy)benzoate) chiral nanoporous template.
The method of claim 1,
The chiral nanoporous template is a chiral nanoporous template, characterized in that it has an inverse helical nanofilament structure.
preparing a precursor mixture comprising a curved nuclear molecule, a reactive mesogenic compound, and a photoinitiator;
preparing a template by photocuring the precursor mixture;
removing the bent nuclear molecule on the template; and
Method for producing a chiral nanoporous template comprising the step of drying the template.
7. The method of claim 6,
The bent nuclear molecule is a nanofission phase (phase) helical nanofilament (helical nanofilament) manufacturing method of a chiral nanoporous template, characterized in that having a phase (phase).
7. The method of claim 6,
The bent nuclear molecule is a method for producing a chiral nanoporous template, characterized in that 1,3-phenylene bis[4-(4-eptyloxyphenyliminomethyl)-benzoate].
9. The method of claim 8,
The reactive mesogenic compound is a method for producing a chiral nanoporous template, characterized in that it consists of a nematic liquid crystal (N-LC) and a reactive monomer.
9. The method of claim 8,
The nematic liquid crystal (N-LC) is a method for producing a chiral nanoporous template, characterized in that 4-cyano-4'-pentylbiphenyl.
9. The method of claim 8,
The reactive monomer is 2-methyl-1,4-phenylene bis(4-(((4-(acryloyl oxy)butoxy)carbonyl)oxy)benzoate).
7. The method of claim 6,
The photoinitiator is a method for producing a chiral nanoporous template, characterized in that DMPAP (2,2-dimethoxy-2-phenylacetophenone).
7. The method of claim 6,
The photocuring method for producing a chiral nanoporous template, characterized in that performed at 80 to 120 ℃
7. The method of claim 6,
The removal of the bent nuclear molecule is a method of manufacturing a chiral nanoporous template, characterized in that using 1,2-dichlorobenzene (1,2-dichlorobenzene).

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