阅读说明：本技术 一种柔性液晶膜及其制备方法 (flexible liquid crystal film and preparation method thereof ) 是由 王斌 段承良 李金鹏 葛洲 陈克复 曾劲松 徐峻 高文花 于 2019-07-15 设计创作，主要内容包括：本发明提供的一种柔性纤维素液晶膜及其制备方法。该方法包括：将木浆与浓硫酸溶液混合,在搅拌状态下进行加热处理,加热后加入水,混合均匀,得到混合液；将混合液进行离心,取上层悬浮液；将上层悬浮液透析,直到悬浮液呈中性,将悬浮液浓缩,得到CNC悬浮液；将CNC悬浮液与三羟甲基乙烷溶液混合均匀,然后进行超声处理,得到CNC/TME混合液；将CNC/TME混合液进行干燥处理,得到所述柔性纤维素液晶膜。通过此方法得到的柔性纤维素液晶膜,具有良好的胆甾相液晶特征。该方法能有效地增加了膜的柔软性和韧性。该制备方法操作简单,过程可控,成本低且易大批量生产,可用于产品防伪、重要文件的加密等方面的应用。(the invention provides a flexible cellulose liquid crystal film and a preparation method thereof. The method comprises the following steps: mixing wood pulp and a concentrated sulfuric acid solution, heating while stirring, adding water after heating, and uniformly mixing to obtain a mixed solution; centrifuging the mixed solution, and taking the upper suspension; dialyzing the upper suspension until the suspension is neutral, and concentrating the suspension to obtain CNC suspension; uniformly mixing the CNC suspension with a trimethylolethane solution, and then carrying out ultrasonic treatment to obtain a CNC/TME mixed solution; and drying the CNC/TME mixed solution to obtain the flexible cellulose liquid crystal film. The flexible cellulose liquid crystal film obtained by the method has good cholesteric liquid crystal characteristics. The method can effectively increase the flexibility and toughness of the film. The preparation method is simple to operate, controllable in process, low in cost, easy for mass production, and applicable to product anti-counterfeiting, encryption of important files and the like.)

1. a preparation method of a flexible cellulose liquid crystal film is characterized by comprising the following steps:

(1) Mixing wood pulp with a concentrated sulfuric acid solution, heating while stirring, adding water, and uniformly mixing to obtain a mixed solution;

(2) centrifuging the mixed solution obtained in the step (1) to obtain an upper suspension;

(3) Pouring the suspension liquid obtained in the step (2) into a dialysis bag, carrying out dialysis treatment until the suspension liquid is neutral, and then soaking the dialysis bag into a polyethylene glycol solution to concentrate the suspension liquid to obtain a CNC suspension liquid;

(4) Uniformly mixing the CNC suspension liquid obtained in the step (3) with a trimethylolethane solution, and then carrying out ultrasonic treatment to obtain a CNC/TME mixed liquid;

(5) and (5) drying the CNC/TME mixed solution obtained in the step (4) to obtain the flexible cellulose liquid crystal film.

2. The method for preparing according to claim 1, wherein the wood pulp of step (1) is softwood pulp or hardwood pulp; the concentration of the wood pulp is 95-100 wt%; the mass percentage concentration of the concentrated sulfuric acid solution is 60-70 wt%; the mass-volume ratio of the oven dry mass of the wood pulp to the volume of the concentrated sulfuric acid solution is 1:8-14 g/mL.

3. The preparation method as claimed in claim 1, wherein the stirring rate in the stirring state in step (1) is 300-400rpm, the temperature of the heat treatment is 45-60 ℃, and the time of the heat treatment is 45-60 min.

4. The method according to claim 1, wherein the volume ratio of the concentrated sulfuric acid solution to water in step (1) is 1: 9-12.

5. the method as set forth in claim 1, wherein the centrifugation in the step (2) is performed 3 to 4 times at a rate of 8000-10000rpm for 10 to 12min at a temperature of 0 to 10 ℃.

6. the method of claim 1, wherein the dialysis bag of step (3) has a molecular weight cut-off of 14000.

7. The preparation method according to claim 1, wherein the concentration of the polyethylene glycol solution in step (3) is 15wt% -20wt%, the molecular weight of the polyethylene glycol is 16000-.

8. the method according to claim 1, wherein the trimethylolethane solution in the step (4) has a concentration of 10 to 20 wt%; the volume ratio of the CNC suspension to the trimethylolethane solution is (6-9) to 1; the temperature of the ultrasonic treatment is 0-5 ℃, the time of the ultrasonic treatment is 10-15min, and the ultrasonic frequency of the ultrasonic treatment is 20-40 KHz.

9. The preparation method according to claim 1, wherein the temperature of the drying treatment in the step (5) is 30-35 ℃, the ambient humidity of the drying treatment is 60-80%, and the time of the drying treatment is 72-96 h.

10. A flexible cellulose liquid crystal film produced by the production method according to any one of claims 1 to 9.

Technical Field

The invention belongs to the field of preparation of functional film materials, and particularly relates to a flexible liquid crystal film and a preparation method thereof.

background

cellulose is the most abundant natural macromolecule in nature and widely exists in plant cell walls and marine animals. The cellulose has the characteristics of low price, no toxicity, reproducibility, good biocompatibility, biodegradability and the like, and the characteristics make the cellulose become a good functional material.

Cellulose is treated by sulfuric acid to obtain a Cellulose Nanocrystalline (CNC) with a rod-shaped rigid morphology, and when a certain critical concentration is reached, the chiral nematic liquid crystal film is obtained through self-assembly. The regular arrangement of the nano-cellulose crystals can be kept in the film, so that the film has special optical properties, such as selective reflection of circularly polarized light, birefringence, circular dichroism and the like, and can be used for the aspects of product anti-counterfeiting, encryption of important documents and the like.

pure cellulose liquid crystal films are very fragile and difficult to completely uncover, which seriously affects the application range and value of the films. In the patent "a bacterial cellulose liquid crystal phase iridescent film and its preparation method and application" (patent application No. CN 201710338909.1), hydroxypropyl guar gum is added to improve the brittleness of the film, but the flexibility of the film is not improved well.

disclosure of Invention

in order to overcome the above-mentioned disadvantages of the prior art, the present invention aims to provide a flexible liquid crystal film and a method for preparing the same. The invention utilizes the viscosity of the polyalcohol solution to introduce the Trimethylolethane (TME) into a liquid crystal film system, thereby improving the flexibility and toughness without influencing the optical performance of the liquid crystal film.

the invention aims to provide a preparation method of a high-flexibility liquid crystal film.

another object of the present invention is to provide a flexible liquid crystal film (flexible cellulose cholesteric liquid crystal film) prepared by the above preparation method.

The purpose of the invention is realized by at least one of the following technical solutions.

The invention provides a preparation method of a flexible cellulose liquid crystal film, which comprises the following steps:

(1) Mixing wood pulp and concentrated sulfuric acid solution, performing heating treatment (acidolysis) under a stirring state, adding deionized water (terminating reaction), and uniformly mixing to obtain a mixed solution (white emulsion);

(2) centrifuging the mixed solution obtained in the step (1) for 3-4 times, and collecting an upper suspension;

(3) pouring the suspension liquid obtained in the step (2) into a dialysis bag, carrying out dialysis treatment, dialyzing with deionized water until the suspension liquid is neutral, and then soaking the dialysis bag into a polyethylene glycol solution (preferably polyethylene glycol with the molecular weight of 20000) to concentrate the suspension liquid to obtain a CNC suspension liquid;

(4) uniformly mixing the CNC suspension liquid obtained in the step (3) with a trimethylolethane solution (TME solution), and then carrying out ultrasonic treatment to obtain a CNC/TME mixed solution;

(5) and (4) drying the CNC/TME mixed solution obtained in the step (4) to obtain the flexible cellulose liquid crystal membrane (CNC/TME membrane).

further, the wood pulp in the step (1) is softwood pulp or hardwood pulp; the concentration of the wood pulp is 95-100 wt%; the mass percentage concentration of the concentrated sulfuric acid solution is 60-70 wt%; the mass-volume ratio of the oven dry mass of the wood pulp to the volume of the concentrated sulfuric acid solution is 1:8-14 g/mL.

Further, the stirring speed in the stirring state in the step (1) is 300-400rpm, the temperature of the heating treatment is 45-60 ℃, and the time of the heating treatment is 45-60 min.

Further, the volume ratio of the concentrated sulfuric acid solution to water in the step (1) is 1: 9-12.

further, the centrifugation treatment time in the step (2) is 3-4 times, the centrifugation treatment speed is 8000-10000rpm, the centrifugation treatment time is 10-12min, and the centrifugation treatment temperature is 0-10 ℃.

Further, the molecular weight cut-off of the dialysis bag in the step (3) is 14000.

further, the concentration of the polyethylene glycol solution in the step (4) is 15-20wt%, preferably 10-15wt%, the molecular weight of the polyethylene glycol is 16000-.

further, the concentration of the trimethylolethane solution in the step (4) is 10wt% -20 wt%; the volume ratio of the CNC suspension to the trimethylolethane solution is (9-6): 1;

preferably, the volume ratio of the CNC suspension to TME solution is 9:1, 8:1, 7:1 or 6: 1.

Further, the temperature of ultrasonic treatment is 0-5 ℃, the time of ultrasonic treatment is 10-15min, and the ultrasonic frequency of ultrasonic treatment is 20-40 KHz.

preferably, the power of the ultrasonic treatment is 200-300W

Further, the temperature of the drying treatment in the step (5) is 30-35 ℃, the humidity of the drying environment is 60-80%, and the time of the drying treatment is 72-96 h.

Preferably, the drying process is drying in a polystyrene petri dish.

the invention provides a flexible cellulose liquid crystal film prepared by the preparation method.

the invention utilizes the viscosity of the polyalcohol solution to increase the flexibility of the film, and the polyalcohol solution does not influence the formation of fingerprint texture in the cholesteric phase.

Compared with the prior art, the invention has the following advantages and beneficial effects:

(1) According to the preparation method provided by the invention, the selected raw material softwood is a renewable resource, and has the advantages of low cost, wide source, degradability, environmental friendliness and the like;

(2) according to the preparation method provided by the invention, hydroxyl on the surface of the cellulose nanocrystal prepared by a sulfuric acid method is oxidized into sulfonic groups, so that the nanorod is negatively charged, and a stable crystalline nano cellulose suspension can be formed under the electrostatic action among crystalline nano celluloses, so that the aggregation of fibers cannot be caused in the self-evaporation process;

(3) According to the preparation method provided by the invention, the adopted raw material, namely trimethylolethane, is a good plasticizer, is tasteless, has good stability and has good glossiness; the solution is mixed with the cellulose nanocrystals, so that the flexibility of the liquid crystal film can be effectively improved;

(4) The preparation method provided by the invention selects an evaporation-induced self-assembly method to prepare the liquid crystal film, and has the advantages of convenient operation, simple condition control and good controllability.

drawings

FIG. 1 is a view of the flexible cellulose liquid crystal film obtained in example 1 observed under an optical microscope.

Detailed Description

The following description of the embodiments of the present invention is provided in connection with the accompanying drawings and examples, but the invention is not limited thereto. It is noted that the processes described below, if not specifically described in detail, are all realizable or understandable by those skilled in the art with reference to the prior art. The reagents or apparatus used are not indicated to the manufacturer, and are considered to be conventional products available by commercial purchase.