CN113186618B - Preparation method of coaxial electrothermal discoloration liquid crystal fiber - Google Patents
Preparation method of coaxial electrothermal discoloration liquid crystal fiber Download PDFInfo
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Abstract
The invention relates to a preparation method of a coaxial electrothermal allochroic liquid crystal fiber, belonging to the technical field of fine chemical engineering and material science. The invention adopts a coaxial micro-flow spinning method to prepare the electro-thermochromism liquid crystal fiber which takes black conductive polymer as an inner conductive layer and polymer dispersed cholesteric liquid crystal as a thermochromism layer, wherein the mass ratio of the black conductive layer to the cholesteric liquid crystal layer is 100: 5 to 30. The electrochromism liquid crystal fiber prepared by the method can reversibly change color under the stimulation of an electric field, can realize a continuous stable state of a certain color change state under the condition of power failure, has bright and changeable color and low driving voltage which is lower than 3.9V (far lower than the safe voltage 12V which is required by the human body in the national standard GB3805-83 safety voltage) and has good solvent resistance and water resistance, and meets the application in the field of wearable color-changing clothes.
Description
Technical Field
The invention relates to a preparation method of a coaxial electrothermal allochroic liquid crystal fiber, belonging to the technical field of fine chemical engineering and material science.
Background
With the development of textile industry, textiles with fashion effect and intelligent response are gradually favored by consumers, and thermochromic materials can be used in the fields of anti-counterfeiting, medical treatment, clothing, sensing and the like. In recent years, since an electric heating coating material can be applied to electronic devices, military fields, household fields, and the like, research on the electric heating coating material is rapidly progressing. The electrothermal allochroic fabric prepared based on compounding of the electrothermal coating and the thermochromic material not only has the performance of common fabric fabrics, but also can intelligently sense the change of external conditions, process information through self sensing, send out instructions and execute actions. The electrochromism material can realize the change of the optical properties (reflectivity, transmittance, absorptivity and the like) of the textile under the stimulation of an electric field, thereby showing the reversible change of color or light transmittance macroscopically, having wide application in the aspects of military protection hidden materials, flexible display, anti-counterfeiting marks, safety warning, artistic ornaments and the like, and being a key component for the intelligent textile to sense and visually feed back the change of the external environment.
Different from the traditional thermochromism material chemical working mechanism, the temperature response color change of the cholesteric liquid crystal is a physical change process, and has the advantages of long service life, quick response time, full spectrum display from a transparent state to a colored state and the like. However, cholesteric liquid crystals flow easily during device flexing and are difficult to shape; meanwhile, the spiral structure of the cholesteric liquid crystal exists in the form of intermolecular force, and the cholesteric liquid crystal is easily influenced by the external environment to lose the thermochromic performance; in addition, most of the conventional liquid crystal devices are rigid devices using glass as a substrate, but with the intelligentization of textile products such as clothes, development of flexible electrochromic devices is urgently needed. These have all greatly limited their further use in textiles. Compared with the traditional two-dimensional or three-dimensional device, the diameter of the fibrous electronic device is between tens of microns and hundreds of microns, the fibrous electronic device belongs to a one-dimensional structure, and the fibrous electronic device has the characteristics of light weight, good flexibility, strong knittability and the like. The advantages of the fiber device such as scalability, self-healing and shape memory are fully utilized, and the fiber device is woven into the intelligent textile which can be bent, deformed, ventilated and water-resistant, and is an important development direction of liquid crystal devices.
At present, more researches are carried out on the electrical heating color-changing fabric at home and abroad, for example, the home and abroad university adopts an in-situ polymerization method to deposit conductive high polymer polypyrrole on the surface of the fabric to obtain a conductive substrate material, and adopts a screen printing mode to print a temperature-changing dye on the other surface of the fabric to prepare the electrical heating color-changing fabric. The method comprises the steps of printing graphene patterns on common silk fabrics by Jiangnan university, then reducing and drying by adopting sodium hydrosulfite, and overprinting a temperature-changing paint with proper size to realize the conductivity and heat-changing color performance of the silk fabrics. And the application research on the electrical heating color-changing liquid crystal textile is less. Chinese patents ZL201711404913.X and ZL201811152977.X are used for preparing liquid crystal microcapsules with smooth surfaces and uniform particle size distribution by an emulsion polymerization method, and are further used for preparing electrochromic coatings to prepare color-changing textiles. However, the above methods cannot meet the requirements of air permeability and flexibility of textiles and the requirement of taking the textiles at a driving voltage lower than the continuous contact safe voltage of 12V (GB3805-83) of a human body. The use of color-changing textile fabrics that conform to the human body is still greatly limited.
Therefore, based on a large-area electrothermal discoloration mechanism, the traditional additional rigid electrode is flexible and integrated, so that the technical bottleneck of the fibrosis of the flexible liquid crystal discoloration material is overcome, the continuous preparation and application of the intelligent electrothermal discoloration liquid crystal fiber capable of being woven are realized, and the problem to be solved is urgently needed.
Disclosure of Invention
In order to solve at least one of the above problems, the present invention is directed to developing flexible electrochromic liquid crystal fibers, which not only expand the non-display application field of liquid crystal, but also improve the production technology of the electrochromic textiles, and meet the diversified demands of the market. The invention provides a preparation and production process of an electrothermal discoloring liquid crystal fiber with a coaxial double-layer structure, which adopts a coaxial microfluid spinning method to prepare the electrothermal discoloring liquid crystal fiber which takes black conductive polymer fiber as an inner conductive layer and polymer dispersed cholesteric liquid crystal as a thermochromic layer, and explores a process method for continuously producing electrothermal discoloring liquid crystal textile devices by preparing large-size electrothermal response discoloring liquid crystal fibers.
The invention overcomes the difficulty that the prior art can not construct a large-scale and long-term stable electrochromism liquid crystal system under the condition of no external electrode action by a method for preparing the electrochromism liquid crystal fiber by microfluid rectification spinning; on the basis of single axial shear force of a wet spinning injection flow, the invention coaxially introduces horizontal force to provide radial shear force for polymer flow and guides cholesteric liquid crystal assembly to form a uniform and flat temperature response color changing liquid crystal layer.
The first object of the present invention is to provide a method for preparing an electrochromism liquid crystal fiber, comprising the steps of:
(1) preparation of black conductive inner layer injection 1: dispersing sodium alginate, glucose and black conductive polymer in a solvent, and uniformly mixing to obtain an injection 1;
(2) preparation of thermochromic liquid crystal layer injection 2: dispersing sodium alginate, glucose and cholesteric liquid crystal in a solvent, and mixing uniformly to obtain an injection 2;
(3) salt solution preparation to drive polymer outward migration: preparing a calcium chloride coagulating bath; specifically, calcium chloride is added into water to be uniformly dispersed to obtain a coagulation bath containing calcium ions;
(4) injecting the injection 1 and the injection 2 into a calcium chloride coagulating bath through a coaxial injector, and leading the sodium alginate to migrate outwards under the guidance of calcium ions to form polymer nanofluid, namely obtaining the electrothermal discoloration liquid crystal microfiber with a coaxial structure.
In one embodiment of the present invention, in the injection solution 1 according to the step (1), the concentration of the sodium alginate is 0.2 to 1.5 wt% relative to the solvent, the concentration of the glucose is 1 to 10wt% relative to the solvent, and the concentration of the black conductive polymer is 0.05 to 0.3 wt% relative to the solvent.
In one embodiment of the present invention, in the injection solution 2 described in step (2), the concentration of sodium alginate in percentage by mass with respect to the solvent is 0.2 to 1.5 wt%, the concentration of glucose in percentage by mass with respect to the solvent is 1 to 10wt%, and the concentration of cholesteric liquid crystal phase in percentage by mass with respect to the solvent is 60 to 90 wt%.
In one embodiment of the invention, the solvent in the injection solutions 1 and 2 is water or a PVA aqueous solution, wherein the concentration of the PVA aqueous solution is 2-10 wt%.
In one embodiment of the invention, the black conductive fiber layer is obtained by dispersing and uniformly mixing sodium alginate, glucose and a black conductive polymer in water; wherein the mass percentage concentration of sodium alginate relative to water is 0.2-1.5 wt%, the mass percentage concentration of glucose relative to water is 1-10 wt%, and the mass percentage concentration of black conductive polymer relative to water is 0.05-0.3 wt%.
In one embodiment of the invention, the cholesteric liquid crystal layer is obtained by adding cholesteric liquid crystal, sodium alginate and glucose into water and uniformly mixing; wherein the mass percentage concentration of sodium alginate relative to water is 0.2-1.5 wt%, the mass percentage concentration of glucose relative to water is 1-10 wt%, and the mass percentage concentration of cholesteric liquid crystal phase relative to water is 60-90 wt%.
In one embodiment of the present invention, the cholesteric liquid crystal in the step (2) is one or more of red cholesteric liquid crystal, yellow cholesteric liquid crystal, and blue cholesteric liquid crystal.
In one embodiment of the present invention, the black conductive polymer in step (1) comprises one or more of graphene polymer, Mxene sheet, polythiophene polymer, and conductive carbon black polymer; further preferred is sodium poly (3,4 ethylenedioxythiophene) polystyrene sulfonate; the black conductive polymer has excellent water-soluble dispersibility and good conductive characteristics.
In one embodiment of the present invention, the cholesteric liquid crystal in step (2) is one or more cholesteric liquid crystals, and the cholesteric phase includes one or more of cholesterol acetate, cholesterol propionate, cholesterol n-butyrate, cholesterol pelargonate, cholesterol oleate, cholesterol linoleate, cholesterol benzoate, cholesterol cinnamate, cholesterol ethyl carbonate, cholesterol oleyl carbonate, cholesterol isostearyl carbonate, cholesterol butenyl crotonate, cholesterol alkenyl carbonate, and chlorinated cholesterol.
In one embodiment of the invention, the cholesteric liquid crystal in the step (2) has a radial topology and an axial wheatear topology inside, and has a steady-state color change characteristic under the action of temperature.
In an embodiment of the invention, the cholesteric liquid crystal in the step (2) needs to be heated to a temperature higher than a clear point (i.e., heated to a state where the mixture is dissolved and transparent) before use, stirred for 1 to 3 hours, cooled to a temperature at which the cholesteric liquid crystal is colored or turbid, heated to be just transparent, and stirred at a constant temperature for 2 to 5 hours.
In one embodiment of the present invention, the molar concentration of calcium chloride in the calcium chloride coagulation bath in step (3) is 10 to 100mM, preferably 50 to 80mM, and more preferably 50 mM; when the concentration of calcium chloride is too low, the internal polymer sodium alginate lacks sufficient traction force, and a stable and smooth hydrogel skin is difficult to form at the interface; the concentration of calcium chloride is too high, and the excessive calcium ions are crosslinked with sodium alginate, so that the liquid crystal fiber is not easy to take out from the receiving liquid.
In one embodiment of the present invention, the preparation method of the calcium chloride coagulation bath in step (3) comprises: adding calcium chloride into water, and performing ultrasonic dispersion uniformly to obtain a coagulation bath containing calcium ions.
In one embodiment of the present invention, the mass ratio of the injection solution 1 to the injection solution 2 in the step (4) is 100: 5 to 30.
In one embodiment of the present invention, the injection speed in step (4) is 0.5-4 mL/min; the injection speed was controlled by a peristaltic pump; preferably, the injection speed is 1-2 mL/min; further preferably, the injection rate is 1.5 mL/min.
In one embodiment of the present invention, the conditions for the coagulation of the fibers in step (4) are: the temperature is 20-30 ℃, and the time is 3-8 min.
In one embodiment of the invention, the sodium alginate used in the preparation is of AR grade and is 90% pure.
In one embodiment of the invention, the mass percentage concentration of sodium alginate used in the steps (1) to (2) in the preparation process is 0.2-1.5 wt%. When the concentration of sodium alginate is too low, the liquid crystal microfiber is not easy to form a stable and smooth hydrogel skin; the concentration of sodium alginate is too high, and the viscosity is too high, so that the rapid arrangement and assembly of the cholesteric liquid crystal layer are not facilitated.
The second purpose of the invention is to provide a coaxial electrothermal allochroic liquid crystal fiber, which has a coaxial double-layer structure, wherein the outer layer is a cholesteric liquid crystal layer, the inner layer is a black conductive fiber layer, and the mass ratio of the black conductive fiber layer to the cholesteric liquid crystal layer is 100: 5 to 30.
In one embodiment of the invention, the coaxial thermochromic liquid crystal fibers are obtained by coaxial spinning.
The third purpose of the invention is the application of the coaxial electrothermal thermochromic liquid crystal fiber in military protective concealing materials, flexible displays, anti-counterfeiting marks or safety warnings or artistic ornaments.
The invention has the beneficial effects that:
(1) the invention aims to combine the conductive inner core fiber with the polymer-based thermochromatic material doped with cholesteric liquid crystal by adopting a coaxial microfluid spinning method to prepare the low-voltage driven thermochromatic liquid crystal fiber, and the fiber can be prepared into a textile by utilizing a textile technology to be combined with an electronic device to form an intelligent color-changing fabric with controllable color. The preparation method is extremely innovative, not only overcomes the defect of high driving voltage of the current electrochromic fiber, expands the application range of the intelligent electrochromic fiber, but also provides a new technical route for the preparation of functional fibers and fabrics, and makes the development of the intelligent fabrics advance. The research based on the electrothermal discoloring fiber technology is scientific and can provide a basis for the application and development of an integrated intelligent fabric system; technically, a new idea and a new method can be provided for realizing the multifunctional intelligent fabric system.
(2) The structure of the electrothermal allochroic liquid crystal fiber provided by the invention is a coaxial double-layer structure, the outer layer is a cholesteric liquid crystal layer, and the inner layer is a black conductive fiber layer. Based on coaxial bilayer structure, release the pitch change that the heat changes cholesteric liquid crystal through the joule heat effect to take place the change of colour, reduction driving voltage that can be very big promotes response rate, thereby promotes its application in flexible wearable intelligent fabrics field. Compared with a color development mode that an electric field of the electrochromic liquid crystal fiber drives liquid crystal to uncoil, when the electrochromic liquid crystal fiber is used, an inner core material of the conducting layer heats under the electrified condition, and a thermochromic liquid crystal layer material of the outer layer plays a color change function under the heat action of the conducting layer. The color change is caused by driving the pitch change of the liquid crystal through electric heating, the required energy is lower, the driving voltage is lower, and the response speed is higher.
(3) The invention prepares the coaxial electrothermal discoloring liquid crystal fiber by microfluid rectification, introduces horizontal polymer flow to provide radial shear force on the basis of single coaxial shear force of wet spinning injection flow, and guides an internal polymer dispersed (cholesteric phase) liquid crystal layer to be assembled to form a chiral liquid crystal fiber layer. The method is simple to operate and easy for large-scale production, and the prepared liquid crystal microfiber has a long-range ordered structure, a stable topological configuration and a controllable optical appearance and has wide application potential in basic soft substance research and specific optical sensing and identification.
(4) The coaxial electrochromism liquid crystal fiber constructed by the invention has adjustable and controllable mechanical property, extremely low driving voltage and high response sensitivity, and can better meet the use requirement of the coaxial electrochromism liquid crystal fiber in the field of wearable textile fabrics attached to human bodies. In addition, the electrothermal discoloring liquid crystal fiber obtained by the invention can realize the change of various colors, has good conductivity and cycle stability, simultaneously shows excellent tensile property, provides a foundation for fiber functionalization and intellectualization, and shows great application value in the aspects of military camouflage, intelligent wearable and visual sensors and the like.
(5) In the method, the black conductive fiber is used as a self-electrified heating source, and together with the outer layer of the calcium alginate polymer, the black conductive fiber protects the middle cholesteric phase liquid crystal from being polluted by the external environment and fixes the relative position. The electrothermal photochromic liquid crystal fiber prepared by the method can reversibly change color under the stimulation of an electric field, can realize a continuous stable state of a certain color change state under the condition of power failure, has gorgeous and changeable color, low driving voltage which is 12V lower than the continuous contact safe voltage of a human body, meets the requirement of GB3805-83, has good solvent resistance and water resistance, can still keep the original stable state electrothermal photochromic performance after the weaving processing treatment, and can meet the requirements of people on individuation and diversity of liquid crystal color development in flexible display and intelligent textiles. The electrothermal thermochromic liquid crystal fiber prepared by the method has good physical, chemical and optical properties and wide application prospect.
(6) The chiral cholesteric liquid crystal array has high content, so that the liquid crystal microfiber displays single color in a natural light visual field, shows uniform interference color in polarized light, has driving voltage lower than the continuous contact safety voltage of a human body, and better meets the textile taking conditions.
(7) The electrochromic liquid crystal fiber with good light transmittance, high mechanical strength and chemical corrosion resistance is prepared by using cholesteric liquid crystal, and simultaneously, the fiber meets the requirements of lower driving voltage and colorful electrochromic capacity and has the bistable characteristic of zero-electric-field color development.
(8) The invention researches a specific preparation method of the electrothermal discoloration liquid crystal fiber, and the electrothermal discoloration liquid crystal fiber without an external electrode is prepared by screening a proper electrode material and liquid crystal ratio and adopting a coaxial microfluid spinning method; the composition proportion and the shape distribution of the cholesteric liquid crystal material play a crucial role in bistable state display, and in the experimental process, it is found that not all cholesteric liquid crystals can be added to realize fiber bistable state color development. The bistable electrochromic selection conditions mainly include two aspects: firstly, calcium alginate (sodium alginate is crosslinked with calcium chloride in coagulation bath to form calcium alginate) and glucose base material have certain binding force with cholesteric liquid crystal, and the orientation distribution state of cholesteric liquid crystal can be fixed in the fiber forming process, so that the bistable display effect is achieved; secondly, the interaction force between the calcium alginate and glucose materials and the cholesteric liquid crystal phase is not too strong, otherwise the response performance of the liquid crystal at the temperature is affected, and the color change effect is lost. Multiple experiments of the inventor prove that only the thickness of the cholesteric liquid crystal intermediate layer is at least more than 20 micrometers, and the ratio of sodium alginate to glucose base material in the cholesteric liquid crystal is about 5-15 wt% so as to meet the steady-state electrochromism characteristic.
Drawings
FIG. 1 is a scanning electron micrograph of a cross section of a coaxial electrochromism liquid crystal fiber.
Detailed Description
The following description of the preferred embodiments of the present invention is provided for the purpose of better illustrating the invention and is not intended to limit the invention thereto. The sodium alginate powder used below was of AR grade, 90% pure, purchased from shanghai alatin biochemical science and technology ltd; glucose powder is AR grade, molecular weight: 180.16, available from Shanghai Aladdin Biotechnology, Inc.
The test method comprises the following steps:
and (3) testing the photoelectric performance: fixing the prepared electrochromism liquid crystal fibers on a rigid substrate, driving the device by adopting a direct-current steady-state power supply, and verifying the electrochromism phenomenon of the display device; the display effect and the electro-optic performance of the liquid crystal fiber device are respectively characterized: the display effect of the device under voltage driving is recorded by real-time photography; and (3) testing an incident light transmittance curve of the device under different external voltages by using the central reflection wavelength of the device in a color development state as a fixed detection wavelength by using a fiber optic spectrometer. During the test, black inner layer fibers were used as blank reference.
The method for testing the loading capacity of the fiber liquid crystal core material comprises the following steps: weighing the electrothermal thermochromic liquid crystal fibers with the weight a, dissolving the fibers by using an ethanol solvent after grinding, centrifugally collecting lower-layer precipitated substances, weighing the lower-layer precipitated substances as b, and calculating the loading capacity c of the fiber liquid crystal core material according to the formula:
water resistance test method and solvent resistance test method: referring to GB/T5211.5-2008, the solvents selected include ethanol, ethylene glycol, acetone.
The color change response time test method comprises the following steps: the time-varying curve of the transmittance at the maximum reflection wavelength of the coaxial electrothermal liquid crystal fiber is recorded in real time under the driving of voltage by an optical fiber spectrometer, and the time for the initial transmittance to reach 90% is taken as the corresponding color-varying response time.
Example 1
A method for preparing an electrochromic liquid crystal fiber by a coaxial microfluid spinning method, comprising the steps of:
(1) preparation of black conductive inner layer injection 1: dispersing 0.05g of sodium alginate powder, 0.5g of glucose powder and 0.15g of poly (3, 4-ethylenedioxythiophene) -poly (styrenesulfonic acid) (Shanghai test Co., Ltd.) in 10mL of water, and magnetically stirring for 10min to prepare a uniform injection 2, wherein the mass fraction of the poly (3, 4-ethylenedioxythiophene) -poly (styrenesulfonic acid) relative to the water is 0.015 wt%;
(2) preparation of electrochromic liquid crystal injection 2: adding 0.05G of sodium alginate powder, 0.5G of glucose powder and 9G of red cholesteric liquid crystal (U10-006G-680, Shijia Chengxi Yonghua company) into 10mL of water, and magnetically stirring for 10min to prepare uniform injection 2, wherein the mass fraction of the red cholesteric liquid crystal phase relative to the water is 90 wt%;
(3) salt solution preparation to drive polymer outward migration: adding 2.775g anhydrous calcium chloride (Shanghai Aladdin Biotechnology Co., Ltd.) into 500mL water, and performing ultrasonic treatment under 100W ultrasonic condition for 5min to obtain 50mM calcium chloride coagulation bath;
(4) preparation of an electrochromism liquid crystal fiber: injecting the injection 1 and the injection 2 obtained in the steps (1) to (2) into the calcium chloride coagulating bath obtained in the step (3) through an injector to obtain the chiral cholesteric phase array, the electrothermal thermochromic liquid crystal fiber with long-range ordered internal structure, stable liquid crystal configuration and controllable optical appearance; wherein the injection speed of the syringe is controlled to be 1.5mL/min by a peristaltic pump.
The prepared liquid crystal fiber with the electrothermal discoloration is subjected to photoelectric property test (shown in table 1) and water and solvent resistance test (shown in table 2).
FIG. 1 is a scanning electron microscope image of a coaxial electrochromic liquid crystal fiber prepared in example 1. It can be seen from fig. 1 that it has a distinct coaxial double-layer structure.
Example 2
Adjusting 90 wt% of red cholesteric liquid crystal in injection 2 of example 1 to 80 wt% of blue cholesteric liquid crystal (U10-006G-480, Shijiacheng Cheng Yonghua Co., Ltd.), and using a two-dimensional Mxene dispersion as the conductive polymer in injection 1, wherein the mass fraction of the Mxene dispersion is 0.3 wt%; the same procedure as in example 1 was otherwise followed to prepare an electrocaloric liquid-crystal microfiber.
The prepared liquid crystal fiber with the electrothermal discoloration is subjected to photoelectric property test (shown in a table 1) and water and solvent resistance test (shown in a table 2). From the test results it can be seen that: the thickness of the liquid crystal layer becomes thinner with the decrease of the concentration of the cholesteric liquid crystal, and the required driving voltage for the electro-thermochromic liquid crystal fiber obtained in comparative example 1 is increased.
Example 3
Preparation of injection 2 of example 1 90 wt% of red cholesteric liquid crystal was adjusted to 70 wt% of yellow cholesteric liquid crystal (U10-006G-580, Shijia Cheng Yonghua Co., Ltd.) and an electrochromism liquid crystal microfiber was prepared by the same preparation procedure as in example 1.
The prepared liquid crystal fiber with the electrothermal discoloration is subjected to photoelectric property test (shown in table 1) and water and solvent resistance test (shown in table 2). From the test results it can be seen that: as the concentration of the cholesteric liquid crystal continues to decrease, the thickness of the liquid crystal layer continues to become thinner and the required driving voltage for the electrochromic liquid crystal fiber obtained in comparative example 1 continues to increase.
Example 4
Preparation of injection 2 of example 1 to 90 wt% of red cholesteric liquid crystal to 60 wt% of red cholesteric liquid crystal (U10-006G-680, Shijia Cheng Yonghua Co., Ltd.) and the same preparation procedure as in example 1 were repeated to prepare an electrochromic liquid crystal microfiber.
The prepared liquid crystal fiber with the electrothermal discoloration is subjected to photoelectric property test (shown in table 1) and water and solvent resistance test (shown in table 2). From the test results it can be seen that: as the concentration of the cholesteric liquid crystal continues to decrease, the thickness of the liquid crystal layer continues to become thinner and the required driving voltage for the electrochromic liquid crystal fiber obtained in comparative example 1 continues to increase.
Example 5 Red cholesteric liquid Crystal concentration optimization
The mass fraction of the red cholesteric liquid crystal phase to water in injection 2 of example 1 was adjusted to 60% and 80%, and the electrocaloric liquid crystal microfibers were prepared by the same preparation procedure as in example 1.
Example 6
The same procedure as in example 1 was repeated except for adjusting the mass concentrations of sodium alginate to water in steps (1) to (2) of example 1 to 0.2%, 1% and 1.5%, respectively, to obtain an electrochromism liquid crystal microfiber.
Example 7
The same procedure as in example 1 was repeated except that the glucose powder concentration in steps (1) to (2) of example 1 was adjusted to 1% and 10% by mass relative to water to obtain an electrocaloric liquid crystal microfiber.
Comparative example 1
The same procedure as in example 1 was repeated except that 90 wt% of the red cholesteric liquid crystal in injection 2 of example 1 was adjusted to 40 wt% of the red cholesteric liquid crystal (U10-006G-680, Shijia Chengxi Yonghua Co., Ltd.) and sodium alginate was used in an amount exchanged with glucose to prepare an electrothermal discoloration liquid crystal microfiber.
The prepared liquid crystal fiber with the electrothermal discoloration is subjected to photoelectric property test (shown in table 1) and water and solvent resistance test (shown in table 2). The electrothermal discoloration liquid crystal fiber obtained in the example 1 has high mechanical strength, excellent ductility and uniform color rendering property, the electrothermal discoloration liquid crystal fiber obtained in the comparative example 1 has low mechanical strength, the fiber elongation is 1.5%, and the tensile stress is 4MPa which is far lower than the mechanical property of the electrothermal discoloration liquid crystal fiber obtained in the example 1; and sodium ions in the injection liquid can continuously migrate into the receiving liquid, and finally, the calcium chloride coagulation bath is also crosslinked, so that the liquid crystal fiber cannot be taken out of the receiving liquid. Meanwhile, due to the reduction of the liquid crystal ratio, the electrothermal discoloration driving voltage of the fiber is increased to be higher than the human body safety voltage.
Comparative example 2
The same procedure as in example 1 was repeated except that the calcium chloride coagulation bath in step (3) of example 1 was changed to absolute ethanol (95%) as the coagulation bath, thereby obtaining an electrochromic liquid crystal fiber.
The liquid crystal fiber prepared as described above was subjected to a photoelectric property test (see table 1) and a water and solvent resistance test (see table 2). From the test results it can be seen that: the electrothermal discoloration liquid crystal fiber obtained in example 1 had high mechanical strength, excellent ductility and uniform color development, and the liquid crystal fiber obtained in comparative example 2 had low mechanical strength and the surface of the liquid crystal fiber was not smooth, resulting in non-uniform color development of the liquid crystal. In the absolute ethyl alcohol coagulating bath, the sodium alginate in the injection is precipitated and hardened, and the water in the liquid crystal fiber migrates to the absolute ethyl alcohol, so that the surface of the liquid crystal fiber is stressed unevenly, a rough surface is formed, the forming cannot be carried out, and the liquid crystal fiber does not have the pyrogen discoloration performance.
Comparative example 3
The mass fraction of the red cholesteric liquid crystal phase to water in injection 2 of example 1 was adjusted to 50% and 95%, and the electrocaloric liquid crystal microfibers were prepared by the same preparation procedure as in example 1.
The liquid crystal fibers having the electrochromism prepared in example 5 and comparative example 3 were subjected to the photoelectric property test (see table 3) and the water and solvent resistance test (see table 4).
Comparative example 4
The same procedure as in example 1 was repeated except for adjusting the mass concentration of sodium alginate relative to water in steps (1) to (2) of example 1 to 0.01% and 20%, respectively, to obtain an electrocaloric liquid-crystal microfiber.
The fibers prepared in example 6 and comparative example 4 and having the electrochromic liquid crystal were subjected to the photoelectric property test (see table 5) and the water and solvent resistance test (see table 6).
Comparative example 5
The same procedure as in example 1 was repeated except that the glucose powder concentration in steps (1) to (2) of example 1 was adjusted to 0.05% and 50% by mass relative to water, thereby obtaining an electrocaloric liquid-crystal microfiber.
The liquid crystal fibers having the electrochromic property prepared in example 7 and comparative example 5 were subjected to the photoelectric property test (see table 7) and the water and solvent resistance test (see table 8).
Comparative example 6
The same procedure as in example 1 was repeated except that the calcium chloride coagulation bath in step (2) of example 1 was changed to a methanol aqueous solution (5 wt%) as the coagulation bath, thereby obtaining an electrothermal discoloration liquid crystal fiber.
As a result, it was found that no fibers could be formed at all.
Comparative example 7
A method for preparing color-changing liquid crystal fibers by a coaxial microfluid spinning method comprises the following steps:
(1) preparation of transparent conductive outer layer injection 1: dispersing 0.05g of sodium alginate powder, 0.5g of glucose powder and 1.5g of silver nanowires (with the length and the diameter of 10 mu m and 60nm) (Sigma company) in 10mL of water, and magnetically stirring for 10min to prepare a uniform injection 1, wherein the mass fraction of the silver nanowires relative to the water is 0.15 wt%;
(2) preparation of black conductive inner layer injection 2: dispersing 0.05g of sodium alginate powder, 0.5g of glucose powder and 0.15g of poly (3, 4-ethylenedioxythiophene) -poly (styrenesulfonic acid) (Shanghai test Co., Ltd.) in 10mL of water, and magnetically stirring for 10min to prepare a uniform injection 2, wherein the mass fraction of the poly (3, 4-ethylenedioxythiophene) -poly (styrenesulfonic acid) relative to the water is 0.015 wt%;
(3) preparation of electrochromic liquid crystal interlayer injection 3: adding 0.05G of sodium alginate powder, 0.5G of glucose powder and 9G of red cholesteric liquid crystal (U10-006G-680, Shijia Chengxi Yonghua company) into 10mL of water, and magnetically stirring for 10min to prepare uniform injection 3, wherein the mass fraction of the red cholesteric liquid crystal phase relative to the water is 90 wt%;
(4) salt solution preparation to drive polymer outward migration: adding 2.775g anhydrous calcium chloride (Shanghai Aladdin Biotechnology Co., Ltd.) into 500mL water, and performing ultrasonic treatment under 100W ultrasonic condition for 5min to obtain 50mM calcium chloride coagulation bath;
(5) preparing electrochromic liquid crystal fibers: injecting the injection 1, the injection 2 and the injection 3 obtained in the steps (1) to (3) into the calcium chloride coagulating bath obtained in the step (4) through an injector to obtain the electrochromic liquid crystal fiber with a chiral cholesteric array, a long-range ordered internal structure, stable liquid crystal configuration and controllable optical appearance; wherein the injection speed of the syringe is controlled to be 1.5mL/min by a peristaltic pump.
The prepared liquid crystal fiber with color change is subjected to photoelectric property test (see table 1) and water and solvent resistance test (see table 2).
As a result, in comparative example 7, compared with example 1, after the silver nanowire transparent conductive outer layer is added on the basis of example 1, the driving voltage is increased from 3.1V to 13.1V (exceeding the human body continuous contact safe voltage of 12V); meanwhile, the response time is increased from 0.8s to 9s, and the response time is greatly increased. The rise of the driving voltage and the extension of the response time are not beneficial to the use in the field of wearable textile fabrics attached to human bodies.
TABLE 1 electro-optical Properties of the electro-thermochromic liquid Crystal fiber materials
Note: "-" indicates that no fibers could be formed.
TABLE 2 Water and solvent resistance of the electrochromically colored liquid crystalline fiber materials
TABLE 3 electro-optical Properties of the electro-thermochromic liquid Crystal fiber materials
TABLE 4 Water and solvent resistance of the electrochromically colored liquid crystalline fiber materials
TABLE 5 electro-optical Properties of the electro-thermochromic liquid Crystal fiber materials
Note: "-" indicates that it is not conductive, i.e., there is no driving voltage.
TABLE 6 Water and solvent resistance of the electrochromically colored liquid crystalline fiber materials
TABLE 7 electro-optical Properties of the electro-thermochromic liquid Crystal fiber materials
Note: "-" indicates that it is not conductive, i.e., there is no driving voltage.
TABLE 8 Water and solvent resistance of the electrochromically colored liquid crystalline fiber materials
Although the present invention has been described with reference to the preferred embodiments, it should be understood that various changes and modifications can be made therein by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (9)
1. A preparation method of a coaxial electrochromism liquid crystal fiber is characterized by comprising the following steps:
(1) preparation of black conductive inner layer injection 1: dispersing sodium alginate, glucose and black conductive polymer in a solvent, and uniformly mixing to obtain an injection 1; or dispersing sodium alginate, glucose and Mxene tablets in a solvent, and uniformly mixing to obtain an injection 1;
(2) preparation of an electrothermal discoloring liquid crystal layer injection 2: dispersing sodium alginate, glucose and cholesteric liquid crystal in a solvent, and mixing uniformly to obtain an injection 2; the cholesteric liquid crystal is one or more of cholesteric liquid crystals, and the cholesteric phase comprises one or more of cholesterol acetate, cholesterol propionate, cholesterol n-butyrate, cholesterol pelargonate, cholesterol oleate, cholesterol linoleate, cholesterol benzoate, cholesterol cinnamate, cholesterol ethyl carbonate, cholesterol oleyl carbonate, cholesterol isostearyl phthalate carbonate, cholesterol butenoate, cholesterol alkenyl carbonate and chlorinated cholesterol; the solvent in the injection 2 is water or a PVA aqueous solution, wherein the concentration of the PVA aqueous solution is 2-10 wt%; the mass percentage concentration of the cholesteric liquid crystal relative to the solvent in the injection 2 is 60-90 wt%, and the cholesteric liquid crystal has a radial topological structure and an axial corncob topological structure inside and has a stable color change characteristic under the action of temperature;
(3) salt solution preparation to drive polymer outward migration: adding calcium chloride into water, and uniformly dispersing to obtain a calcium chloride coagulating bath;
(4) and injecting the injection 1 and the injection 2 into a calcium chloride coagulation bath through a coaxial injector, and guiding sodium alginate to migrate outwards by calcium ions in the calcium chloride coagulation bath to form polymer nanofluid, so as to obtain the coaxial electrothermal discoloration liquid crystal fiber with the double-layer structure.
2. The method for preparing a coaxial electrochromic liquid crystal fiber according to claim 1, wherein the mass ratio of the injection solution 1 to the injection solution 2 in the step (4) is 100: 5 to 30.
3. The method for preparing a coaxial electrochromism liquid crystal fiber as claimed in claim 1 or 2, wherein in the step (2), the glucose concentration of the injection 2 relative to the solvent is 1-10 wt%; the concentration of sodium alginate in the injection 2 is 0.2-1.5 wt% of the solvent.
4. The method for preparing a coaxial electrochromism liquid crystal fiber as set forth in claim 1 or 2, wherein the concentration of sodium alginate in the injection solution 1 in the step (1) is 0.2-1.5 wt% relative to the solvent, the concentration of glucose in the injection solution is 1-10 wt% relative to the solvent, and the concentration of the black conductive polymer in the injection solution is 0.05-0.3 wt% relative to the solvent.
5. The method for preparing a coaxial electrochromic liquid crystal fiber according to claim 1 or 2, wherein the cholesteric liquid crystal in the step (2) is one or more of red cholesteric liquid crystal, yellow cholesteric liquid crystal and blue cholesteric liquid crystal.
6. The method for preparing a coaxial electrochromism liquid crystal fiber as claimed in claim 1 or 2, wherein the molar concentration of calcium chloride in the calcium chloride coagulating bath in the step (3) is 10-100 mM.
7. The method for preparing a coaxial thermochromic liquid crystal fiber according to claim 1, wherein the black conductive polymer in step (1) comprises one or more of a graphene polymer, a polythiophene polymer and a conductive carbon black polymer.
8. The coaxial electrothermal discoloration liquid crystal fiber with the coaxial double-layer structure prepared by the method of any one of claims 1 to 7, wherein the outer layer is a cholesteric liquid crystal layer, the inner layer is a black conductive fiber layer, and the mass ratio of the black conductive fiber layer to the cholesteric liquid crystal layer is 100: 5 to 30.
9. Use of the coaxial electrochromic liquid crystal fiber according to claim 8 in military protective concealment materials, flexible displays, anti-counterfeiting marks or safety warnings or artistic ornaments.
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