阅读说明：本技术 一种二维限域自组装制备纳米纤维素液晶微纤维的方法 (Method for preparing nano cellulose liquid crystal microfiber through two-dimensional domain-limited self-assembly ) 是由 武培怡 刘艳军 于 2019-09-16 设计创作，主要内容包括：本发明涉及一种二维限域自组装制备纳米纤维素液晶微纤维的方法。该方法包括：将海藻酸钠和纤维素纳米晶的混合溶液注射到氯化钙接受液中。该方法操作简单、易规模化生产、原料来源广、可持续,制备出的液晶微纤维具有一定的机械强度和拉伸性能,在加密,可穿戴设备,光学和机械传感材料等方面也有广阔的应用前景。(The invention relates to a method for preparing a nano cellulose liquid crystal microfiber by two-dimensional domain-limited self-assembly. The method comprises the following steps: and injecting the mixed solution of sodium alginate and cellulose nanocrystalline into a calcium chloride receiving solution. The method is simple to operate, easy for large-scale production, wide in raw material source and sustainable, and the prepared liquid crystal microfiber has certain mechanical strength and tensile property and has wide application prospects in the aspects of encryption, wearable equipment, optical and mechanical sensing materials and the like.)

1. A method for preparing a nano cellulose liquid crystal microfiber by two-dimensional domain-limited self-assembly, comprising:

(1) adding sodium alginate into a cellulose nanocrystalline CNC solution, and stirring to obtain an injection, wherein the mass percent concentration of the sodium alginate in the injection is 0.2-2 wt%, and the mass percent concentration of the CNC is 1-3 wt%;

(2) adding calcium chloride into deionized water, and performing ultrasonic dispersion to obtain a calcium chloride receiving solution, wherein the molar concentration of the calcium chloride receiving solution is 10-100 mM;

(3) and (3) injecting the injection in the step (1) into the calcium chloride receiving solution in the step (2) through an injector to obtain the nano cellulose liquid crystal microfiber, wherein the injection speed is 0.25-4 mL/min.

2. The method as claimed in claim 1, wherein the CNC particle size in step (1) is 150-300 nm; stirring at room temperature for 10-20 min.

3. The method according to claim 1, wherein the concentration of sodium alginate in the injection solution in step (1) is 0.5-1 wt%; the mass percentage concentration of CNC in the injection is 1.5-2.5 wt%.

4. The method according to claim 3, wherein the concentration of sodium alginate in the injection solution in step (1) is 0.5 wt%; the mass percentage concentration of CNC in the injection is 2 wt%.

5. The method according to claim 1, wherein the ultrasonic dispersion time in the step (2) is 3-5 min.

6. The method according to claim 1, wherein the molar concentration of the calcium chloride-containing receiving solution in the step (2) is 50-80 mM.

7. The method according to claim 1, wherein the injection rate in the step (3) is 0.5-2 mL/min; the injection speed was controlled by a peristaltic pump.

8. A nanocellulose liquid crystal microfibre prepared by the process as claimed in claim 1.

9. Use of a nanocellulose liquid crystal microfibre prepared by the process as claimed in claim 1.

Technical Field

The invention belongs to the field of preparation of nano-cellulose liquid crystal microfibers, and particularly relates to a method for preparing the nano-cellulose liquid crystal microfibers through two-dimensional domain-limited self-assembly.

Background

The complex and ingenious multilevel structure is ubiquitous in nature. Organisms adapt to the external environment by perfectly regulating the interaction between the constituent modules to assemble a wide variety of multifunctional structures (Ulrike g.k.wegst, Hao Bai, Eduardo Saiz, Antoni p.tomsia, and Robert o.ritchai, nat. mater.,2015,14, 23-36.). Among them, helical structures frequently occur in nature and play an important role in the growth and reproduction of organisms (VivekSharma, Matija Crne, Jung Ok Park and Mohan Srinivasarao, Science,2009,325,449-451.), but the natural assembly process is currently poorly understood. Therefore, artificial imitation of similar structures is of great importance to elucidate the source of self-assembly of complex helical structures in nature, and by editing the functionality of different modules in a multilevel structure, biomimetic materials with a collective versatility can be assembled (Andre r. studart, angelw. chem. int. ed.,2015,54, 2-19.). However, controlling the ordering of structures across multiple scales (from nanometers to hundreds of micrometers) in man-made materials is extremely challenging.

Cellulose Nanocrystals (CNC) with a length of 100-350nm are rod-like natural polymer nanomaterials assembled from chiral D-glucopyranose and have birefringent optical properties (Ivan Usov, Gustav)Jozef Adamcik,Stephan Handschin,Christina Schütz,Andreas Fall,Lennartand rafvae Mezzenga, nat. commun.,2015,6, 7564.). CNC can spontaneously assemble into levorotatory cholesteric liquid crystal arrays (helices) on the nano scale due to the retention of some chirality, and this chiral liquid crystal structure can be maintained when dried into a film, forming photonic crystal films with vivid iridescent colors (Hongzhi Zheng, Wanru Li, Wen Li, Xiaojun Wang, Zhiyong Tang, seaan Xiao-An Zhang, and Yan Xu, adv. mater, 2018,30, 1705948.).

At present, CNC self-assembly is mainly realized by coating a CNC solution on a one-dimensional plane through natural evaporation, and the solution concentration, the CNC particle size, the solvent type and the evaporation rate can only be adjusted in the process to regulate and control the performance of a photonic crystal film (Richard M. Parker, Giulia Guidetti, Cyan A. Williams, Tianheng Zhuao, Aurimas Narkevicius, Silvia Vignilini, and Bruno Frka-Petesic, adv. Mater.2017,29,1704477.). The assembly strategy is simple, the editability is poor, and a specific functional structure cannot be formed. The method is different from the method that the CNC on a one-dimensional plane moves freely in the self-assembly process, the CNC is limited in the space movement in the assembly process in the limited-area geometry, the customized regulation and control of the CNC multi-stage structure can be realized, and the bionic material with a specific function structure is assembled. The method for preparing the nano-cellulose liquid crystal microfiber by two-dimensional limited domain self-assembly reveals the self-assembly mechanism of CNC in the limited domain geometry, provides a theoretical basis for the synthesis of multifunctional bionic materials, and the photonic crystal nano-cellulose composite material with the multilevel structure has wide application prospects in the aspects of polarized light information encryption, biological coding, optical data storage, optical devices and the like. In addition, the CNC multi-level structure can be used as a template to construct other functional materials by introducing optical, electrical, magnetic and other functional materials (Kenneth C.K. Cheng, MarcoA. Bedolla-Pantoja, Young-Kim, Jason V.Gregory, Fan Xie, Alexander de France, Christoph Hussal, Kai Sun, Nicholas L.Abbott, Joerg Lahann, Science,2018,362, 804-.

Disclosure of Invention

The invention aims to solve the technical problem of providing a method for preparing nano cellulose liquid crystal microfiber by two-dimensional domain-limited self-assembly, so as to overcome the defects of poor editability, incapability of forming a specific functional structure and the like when CNC self-assembly is realized on a one-dimensional plane through natural evaporation in the prior art.

The invention provides a method for preparing a nano cellulose liquid crystal microfiber by two-dimensional domain-limited self-assembly, which comprises the following steps:

(1) adding sodium alginate into a cellulose nanocrystalline CNC solution, and stirring to obtain an injection, wherein the mass percent concentration of the sodium alginate in the injection is 0.2-2 wt%, and the mass percent concentration of the CNC is 1-3 wt%;

(2) adding calcium chloride into deionized water, and performing ultrasonic dispersion to obtain a calcium chloride receiving solution, wherein the molar concentration of the calcium chloride receiving solution is 10-100 mM;

(3) and (3) injecting the injection in the step (1) into the calcium chloride receiving solution in the step (2) through an injector to obtain the nano cellulose liquid crystal microfiber, wherein the injection speed is 0.25-4 mL/min.

The particle size of the CNC in the step (1) is 150-300 nm.

In the step (1), the stirring temperature is room temperature, and the stirring time is 10-20 min.

In the step (1), the sodium alginate is in AR grade, and the purity is 90%.

The mass percentage concentration of the sodium alginate in the injection in the step (1) is 0.5-1 wt%.

The mass percentage concentration of the sodium alginate in the injection is 0.5 wt%.

The mass percentage concentration of CNC in the injection in the step (1) is 1-5 wt%.

The mass percentage concentration of CNC in the injection is 2 wt%.

The ultrasonic dispersion time in the step (2) is 3-5 min.

The molar concentration of the calcium chloride receiving solution in the step (2) is 50-80 mM.

The molar concentration of the calcium chloride receiving solution is 50 mM.

The injection speed in the step (3) is 0.5-2 mL/min; the injection speed was controlled by a peristaltic pump.

The injection rate was 1 mL/min.

The nano cellulose liquid crystal microfiber in the step (3) has an ordered cholesteric array.

The invention also provides the nano cellulose liquid crystal microfiber prepared by the method.

The invention also provides an application of the nano cellulose liquid crystal microfiber prepared by the method.

At present, the self-assembly process of CNC is controlled through a geometric space, customized regulation and control of a multi-stage structure are realized, and systematic research is not yet carried out. The constructed nano-cellulose composite material with the multilevel structure has wide application prospect in the aspects of polarized light information encryption, biological coding, optical data storage, optical devices and the like. In addition, the CNC multi-level structure can be used as a template to construct other functional materials by introducing optical, electrical, magnetic and other functional materials.

The invention uses an injector to inject the mixed solution of cellulose nanocrystalline and sodium alginate into calcium chloride solution, thus obtaining the nano cellulose liquid crystal microfiber with the surface coated with a calcium alginate gel layer. The method has the advantages of simple operation, easy large-scale production, wide raw material source and sustainability, and the prepared liquid crystal microfiber has wide application prospect in the aspects of encryption, wearable equipment, optical and mechanical sensing materials and the like.

In the assembling process, the sodium alginate in the injection liquid migrates outwards and is crosslinked with calcium ions in the calcium chloride receiving liquid at the interface of the liquid crystal microfiber to form a smooth and stable gel layer, and a CNC assembled two-dimensional limited space is provided.

In the invention, the sodium alginate is in AR grade, the purity is 90%, the mass percentage concentration of the sodium alginate is 0.2-2 wt%, and when the concentration of the sodium alginate is too low, the liquid crystal microfiber is not easy to form a stable and smooth outer gel layer serving as a two-dimensional geometric restriction interface; the concentration of sodium alginate is too high, and due to the limitation of polymer molecular chains, the formation of ordered cholesteric arrays in the CNC assembling process is not facilitated.

The molar concentration of calcium chloride in the calcium chloride receiving liquid is 10-100mM, and when the concentration of the calcium chloride is too low, the liquid crystal microfiber is not easy to form a stable and smooth outer gel layer serving as a two-dimensional geometric restriction interface; the calcium chloride concentration is too high, and the excessive calcium ions are crosslinked with the sodium alginate, so that the liquid crystal microfiber is not easy to take out of the receiving liquid.

The liquid crystal microfiber has an ordered cholesteric array, so that the liquid crystal microfiber shows a uniform liquid crystal color under polarized light and can selectively reflect circular dichroism.

Advantageous effects

(1) The assembly equipment only needs an injector, has simple assembly strategy and high efficiency, can be produced in a large scale and is beneficial to industrialized popularization and use.

(2) The invention can realize the control of the pitch of the liquid crystal microfiber cholesteric array by controlling the flow rate of the injection.

(3) In the invention, the two-dimensional confinement space provides a closed curved surface in the radial direction of the liquid crystal fiber to be used as a rivet interface for CNC self-assembly, so that the CNC cholesteric array presents radial arrangement, and the construction of a specific functional structure is realized.

(4) The liquid crystal microfiber obtained by the invention shows uniform color under polarized light, and also has selective reflection circular dichroism, and the liquid crystal fiber rotates rightwards to display uniform blue and rotates leftwards to display uniform red.

(5) The liquid crystal microfiber obtained by the invention shows uniform color under polarized light, and the color is regularly switched along with the change of axial stress, and the color of the liquid crystal microfiber is gradually switched from blue to red when the stress is increased.

(6) The liquid crystal microfiber obtained by the method has high mechanical strength, tensile stress of 0.3MPa and elongation of 150%, and the dry liquid crystal microfiber has tensile stress of 120MPa and elongation of close to 5%.

Drawings

FIG. 1 is a schematic diagram of the preparation process of the nano-cellulose liquid-crystal microfiber and the obtained nano-cellulose liquid-crystal microfiber, and a topography under a polarized light microscope.

Fig. 2 is a schematic view of a CNC ordered cholesteric structure in accordance with the present invention.

Fig. 3 is an atomic force microscope image of CNC in the present invention.

Fig. 4 is a particle size distribution diagram of CNC in the present invention.

FIG. 5 is a tensile stress-strain diagram of the nanocellulose liquid crystal microfibrils prepared in example 1 at different states of water content.

FIG. 6 is a graph showing the formation of liquid crystal microfibers at different injection rates (0.25-4.0mL/min) during the preparation of nanocellulose liquid crystal microfibers in example 1.

FIG. 7 is a diagram of an assembly apparatus in the process of preparing a nanocellulose liquid crystal microfiber of the present invention.

FIG. 8 is a radial scanning electron microscope image of the nanocellulose liquid-crystal microfibrils prepared in example 1.

FIG. 9 is a graph showing the regular color change with angle switching and the regular color change with increasing tensile stress of the nanocellulose liquid crystal microfibrils prepared in example 1 under a polarized light microscope.

Detailed Description

The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Further, it should be understood that various changes or modifications of the present invention may be made by those skilled in the art after reading the teaching of the present invention, and such equivalents may fall within the scope of the present invention as defined in the appended claims.