KR-20260063375-A - SMART FIBER UTILIZING CHOLESTERIC LIQUID CRYSTAL ELASTOMER

KR20260063375AKR 20260063375 AKR20260063375 AKR 20260063375AKR-20260063375-A

Abstract

The present invention relates to a smart fiber utilizing a cholesteric liquid crystal elastomer. According to one embodiment, a smart fiber utilizing a cholesteric liquid crystal elastomer may be provided, comprising a core-sheath composite consisting of a core portion and a liquid crystal elastomer portion that surrounds the outer surface of the core portion and has mechanical color change properties within a preset color change range, wherein the liquid crystal elastomer portion comprises a helical liquid crystal layer formed by aligning a plurality of anisotropic helical liquid crystal structures, which are composed of a plurality of unit liquid crystal molecules and form a preset conical angle with respect to a twist axis, in a unidirectional direction.

Inventors

김대석
엄영호
정유진
이영은

Assignees

국립부경대학교 산학협력단
한양대학교 산학협력단

Dates

Publication Date: 20260507
Application Date: 20241030

Claims (10)

Core part; and A core-sheath composite comprising a liquid crystal elastomer portion that surrounds the outer surface of the core portion and has mechanical color change properties within a preset color change range, and The above liquid crystal elastomer part is, A helical liquid crystal layer comprising a plurality of anisotropic helical liquid crystal structures, each composed of a plurality of unit liquid crystal molecules and forming a pre-set conical angle with respect to a twist axis, which are aligned in a unidirectional manner. Smart textile utilizing cholesteric liquid crystal elastomer.
In Article 1, The above core part is, A thermoplastic elastomer (TPE) core fiber comprising Smart textile utilizing cholesteric liquid crystal elastomer.
In Article 2, The above thermoplastic elastomer (TPE) core fiber is, It comprises a thermoplastic elastomer resin and carbon black (CB), and The content of the carbon black (CB) satisfies the range of 0.08 to 2 wt% with respect to 100 wt% of the thermoplastic elastomer resin, and The above thermoplastic elastomer (TPE) core fiber is, Having an elastic modulus of 10 to 25 MPa, Smart textile utilizing cholesteric liquid crystal elastomer.
In Paragraph 3, The above liquid crystal elastomer part is, Reflect light in the visible wavelength range from incident light through Bragg reflection, A smart fiber utilizing a cholesteric liquid crystal elastomer, wherein the above visible light wavelength range is set based on the average refractive index (n) of the liquid crystal elastomer part, the cholesteric pitch (P) of the anisotropic helical liquid crystal structures included in the liquid crystal elastomer part, and the angle (θ) between the incident light and the twist axis to satisfy the following equation. (Here, n is the average refractive index, P is the cholesteric pitch, and θ is the angle between the incident light and the twist axis) Smart textile utilizing cholesteric liquid crystal elastomer.
In Paragraph 4, The above liquid crystal elastomer part is, exhibiting mechanical discoloration due to a change in the cholesteric pitch (P) of the spiral liquid crystal structures through the application of an external load, Smart textile utilizing cholesteric liquid crystal elastomer.
In Article 5, The above liquid crystal elastomer part is, It further includes a chiral dopant having the property of diffusing in the direction in which ultraviolet rays are irradiated, and The initial reflection wavelength band is shifted by controlling the concentration of the above chiral dopant, and Selectively reflecting light in the visible light wavelength range corresponding to the shifted initial reflection wavelength band, Smart textile utilizing cholesteric liquid crystal elastomer.
In Article 6, The above-mentioned core-sheath complex is, As the reordering of the anisotropic helical liquid crystal structure included in the liquid crystal elastomer is induced by the elastic recovery force of the core portion, having low-hysteresis characteristics, Smart textile utilizing cholesteric liquid crystal elastomer.
The method comprises the step of manufacturing a core-sheath composite comprising: a core portion; and a liquid crystal elastomer portion that surrounds the outer surface of the core portion and has mechanical color change properties within a preset color change range; wherein the method comprises: a core portion; and a liquid crystal elastomer portion that surrounds the outer surface of the core portion and has mechanical color change properties within a preset color change range. The above liquid crystal elastomer part is, A helical liquid crystal layer comprising a plurality of anisotropic helical liquid crystal structures, each composed of a plurality of unit liquid crystal molecules and forming a pre-set conical angle with respect to a twist axis, which are aligned in a unidirectional manner. Method for manufacturing smart textiles using cholesteric liquid crystal elastomer.
In Article 8, The step of manufacturing the above core-sheath composite is, A core preparation step in which a core part is prepared through a melt spinning process after mixing a pellet-type thermoplastic elastomer (TPE) resin and carbon black (CB); An oligomer preparation step of preparing an LC oligomer through a washing process, a drying process, and a filtering process, after obtaining a reaction mixture by mixing a reactive monomer, a solvent, a thiol compound, and a catalyst; A precursor obtaining step of obtaining a liquid crystal elastomer precursor by mixing a prepared LC oligomer, the reactive monomer, a photoinitiator, a thermal polymerization inhibitor, and a chiral dopant, and then stirring; A precursor heating step of placing the obtained liquid crystal elastomer precursor into a chamber and heating it to a preset temperature; and A composite obtaining step comprising: a melting extrusion process and a UV exposure process in which a prepared core portion is impregnated into a chamber containing a heated liquid crystal elastomer precursor, and then the impregnated core portion is compressed and pulverized to obtain a core-sheath composite; Method for manufacturing smart textiles using cholesteric liquid crystal elastomer.
In Article 9, In the above precursor heating step, The above-mentioned pre-set heating temperature is a temperature 10% to 20% higher or lower than the glass transition temperature (Tg) of the obtained liquid crystal elastomer precursor, and The above glass transition temperature is the temperature at which an isotropic liquid crystal structure undergoes a phase transition to an anisotropic helical liquid crystal structure, and In the above-mentioned complex obtaining step, Due to the shear stress applied through the melting extrusion process, the anisotropic helical liquid crystal structure is oriented in a direction perpendicular to the central axis of the core part. Method for manufacturing smart textiles using cholesteric liquid crystal elastomer.

Description

Smart Fiber Utilizing Cholesteric Liquid Crystal Elastomer The present invention relates to a smart fiber utilizing a cholesteric liquid crystal elastomer. Smart textiles are fabrics that perform information transmission functions by combining advanced technology to detect changes or stimuli in the external environment, and are being utilized in various fields such as healthcare, environmental monitoring, biosensing, motion detection, and smart sportswear. Mechanochromic materials possess the characteristic of changing color as their internal molecular structure or arrangement changes when mechanical deformation, such as stretching or bending, is applied. By fabricating mechanochromic fibers utilizing this property, it is possible to manufacture functional smart fibers capable of immediately detecting mechanical deformation or loads caused by the external environment. Mechanochromic fibers of a commercially viable level must satisfy the conditions of (1) a wide color change range with high saturation, and (2) high mechanical properties and resilience. Previously studied mechanochromic fibers exhibit mechanical color change characteristics in which inelastic nanoparticles arranged at regular intervals within the elastomer reflect specific colors and the arrangement of particles changes due to physical deformation of the fiber. However, there is a limitation in that there is a trade-off between saturation and mechanical properties depending on the arrangement of the nanoparticles. Meanwhile, another notable mechanochromic material is the cholesteric liquid crystal elastomer. Due to added chiral dopants, the molecules form a helical structure that selectively reflects light of specific wavelengths. They exhibit color-changing properties as the pitch of the helical structure changes in response to external mechanical deformation. Recently studied cholesteric liquid crystal elastomer fibers possess a broad color-changing wavelength range of approximately 155 nm, but exhibit low mechanical properties and resilience. This is attributed to the inherent characteristics of liquid crystal elastomer materials with soft elasticity, as a delay in elastic recovery occurs due to the rearrangement of liquid crystal molecules after deformation. These limitations hinder the immediate detection of mechanical deformation, which is essential for commercial-scale application. To address the aforementioned issues, the present invention realizes a core-shell composite composed of a TPE core fiber possessing high strength and high resilience and a cholesteric liquid crystal elastomer outer shell. This structure integrates the mechanochromic properties of the cholesteric liquid crystal elastomer while maintaining the high physical properties and resilience of the TPE, thereby enabling commercial-level mechanical deformation perception and rapid color change. Furthermore, by adding carbon black to the TPE core fiber, strength can be selectively controlled, and consequently, a desired level of discoloration can be set within the required load range. FIG. 1 is a drawing for explaining a smart fiber utilizing a cholesteric liquid crystal elastomer according to one embodiment of the present invention. FIG. 2 is a drawing for explaining a liquid crystal elastomer part according to one embodiment of the present invention. FIG. 3 is a flowchart illustrating a method for manufacturing a smart fiber using a cholesteric liquid crystal elastomer according to one embodiment of the present invention. Figure 4 is a diagram showing the microstructure evaluation results of the liquid crystal elastomer part according to the heating temperature. Figure 5 is a diagram showing the results of the microstructure evaluation of the liquid crystal elastomer part. Figure 6 is a diagram showing the results of the mechanical discoloration characteristic evaluation of smart fibers according to load. Figure 7 is a diagram showing the hysteresis evaluation results of smart textiles. Figure 8 is a diagram showing the results of the evaluation of the mechanical and optical properties of smart fibers. Figure 9 is a diagram showing a practical example of a smart textile. In order to fully understand the structure and effects of the present invention, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. The present invention is not limited to the embodiments disclosed below, but can be implemented in various forms and subject to various modifications and changes. The description of the embodiments is provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention. In the attached drawings, the components are depicted enlarged from their actual size for convenience of explanation, and the proportions of each component may be exaggerated or reduced. The terms used in this specification are for describing embodiments a