阅读说明：本技术 用于制备液晶弹性体纤维的方法及液晶弹性体纤维 (Method for producing liquid crystal elastomer fiber and liquid crystal elastomer fiber ) 是由 杨忠强 廖威 于 2021-08-23 设计创作，主要内容包括：本申请实施例提供一种用于制备液晶弹性体纤维的方法及液晶弹性体纤维。本申请实施例第一方面提供一种用于制备液晶弹性体纤维的方法,包括：提供纤维前驱物,其中,纤维前驱物包括至少一种液晶弹性体寡聚物,液晶弹性体寡聚物包含液晶基元结构单元与柔性链段,液晶弹性体寡聚物的聚合度在2～100的范围内；挤出纤维前驱物形成纤维前驱体,并使纤维前驱体在自身重力作用下拉伸获得预取向纤维；交联固化预取向纤维,以获得液晶弹性体纤维。减少了设置拉伸装置对纤维前驱体进行拉伸的工序以及拉伸设备投入,简化生产工序提高生产效率的同时降低了生产成本。(The embodiment of the application provides a method for preparing liquid crystal elastomer fiber and the liquid crystal elastomer fiber. A first aspect of embodiments of the present application provides a method for preparing a liquid crystal elastomer fiber, comprising: providing a fiber precursor, wherein the fiber precursor comprises at least one liquid crystal elastomer oligomer, the liquid crystal elastomer oligomer comprises a liquid crystal unit structural unit and a flexible chain segment, and the polymerization degree of the liquid crystal elastomer oligomer is within the range of 2-100; extruding a fiber precursor to form a fiber precursor, and drawing the fiber precursor under the action of self gravity to obtain a pre-oriented fiber; the pre-oriented fibers are cross-linked and cured to obtain liquid crystalline elastomer fibers. The process of setting the stretching device to stretch the fiber precursor and the investment of stretching equipment are reduced, the production process is simplified, the production efficiency is improved, and meanwhile, the production cost is reduced.)

1. A process for preparing a liquid crystalline elastomeric fiber, comprising:

providing a fiber precursor, wherein the fiber precursor comprises at least one liquid crystal elastomer oligomer, the liquid crystal elastomer oligomer comprises a liquid crystal unit structural unit and a flexible chain segment, and the polymerization degree of the liquid crystal elastomer oligomer is within the range of 2-100;

extruding the fiber precursor to form a fiber precursor, and drawing the fiber precursor under the action of self gravity to obtain a pre-oriented fiber;

crosslinking and curing the pre-oriented fibers to obtain liquid crystalline elastomer fibers.

2. The method for preparing a liquid crystal elastomer fiber according to claim 1, wherein in the step of providing a fiber precursor, the degree of polymerization of the liquid crystal elastomer oligomer is in a range of 3 to 10.

3. The method for preparing a liquid crystal elastomer fiber according to claim 1, wherein the step of extruding the fiber precursor to form a fiber precursor comprises:

heating the fiber precursor to enable the fiber precursor to reach a preset temperature T when being extruded, wherein the value range of the preset temperature T is 20-200 ℃;

preferably, the preset temperature T is 25-100 ℃.

4. The process for the preparation of liquid-crystalline elastomeric fibers according to claim 1, wherein in the step of cross-linking and curing the pre-oriented fibers:

and crosslinking and curing the pre-oriented fibers by at least one of a photo-initiated crosslinking mode, an atmosphere-initiated crosslinking mode and a ray-initiated crosslinking mode.

5. The process for preparing a liquid-crystalline elastomeric fiber according to claim 1, wherein in the step of extruding the fiber precursor to form a fiber precursor:

extruding the fiber precursor wrapped with the fluid to be dried to obtain the fiber precursor with the fluid to be dried as a central core;

preferably, the method for preparing a liquid crystal elastomer fiber further comprises:

drying the liquid crystal elastomer fiber containing the fluid to be dried to obtain a liquid crystal elastomer hollow fiber having a hollow structure.

6. The process for preparing a liquid-crystalline elastomeric fiber according to claim 1, wherein in the step of extruding the fiber precursor to form a fiber precursor:

and extruding a plurality of fiber precursors simultaneously to obtain the fiber precursor with a plurality of fiber precursor layers, wherein every two adjacent fiber precursor layers are different from each other.

7. The method for producing a liquid-crystalline elastomer fiber as claimed in claim 1, wherein in the step of extruding the fiber precursor to form a fiber precursor,

the extrusion height of the fiber precursor ranges from 1cm to 100 cm;

preferably, the extrusion height of the fiber precursor ranges from 10cm to 40 cm;

preferably, the extrusion height of the fiber precursor ranges from 15cm to 25 cm.

8. The method for preparing a liquid crystal elastomer fiber as claimed in any one of claims 1 to 7, wherein in the step of extruding the fiber precursor to form a fiber precursor,

the shear viscosity of the fiber precursor ranges from 0.1 Pa · s to 100000Pa · s;

preferably, the shear viscosity of the fiber precursor ranges from 10 to 1000 pas.

9. The liquid crystal elastomer fiber is characterized by comprising a liquid crystal elastomer oligomer, wherein the polymerization degree of the liquid crystal elastomer oligomer is within the range of 2-100;

preferably, the polymerization degree of the liquid crystal elastomer oligomer is in the range of 4 to 8.

10. The liquid crystal elastomer fiber as claimed in claim 9, wherein the liquid crystal elastomer oligomer has a Tg of-13.4 ℃ and a T of_NI75.8 ℃, Tg of the liquid crystal elastomer fiber is 1.8 ℃, and T of the liquid crystal elastomer fiber_NIIs 102.8 ℃;

preferably, the liquid crystal elastomer oligomer has a thermal response deformation rate of 25% to 40%.

Technical Field

The invention relates to the technical field of liquid crystal elastomer fibers, in particular to a method for preparing liquid crystal elastomer fibers and the liquid crystal elastomer fibers.

Background

The general method for preparing the liquid crystal elastomer fiber by melt extrusion requires complex process steps in the extrusion molding process, has high processing cost and low efficiency of preparing the liquid crystal elastomer fiber, and is difficult to realize efficient and continuous processing and preparation of the liquid crystal elastomer fiber.

Therefore, a new method for preparing liquid crystal elastomer fiber is urgently needed.

Disclosure of Invention

A first aspect of embodiments of the present application provides a method for preparing a liquid crystal elastomer fiber, comprising:

providing a fiber precursor, wherein the fiber precursor comprises at least one liquid crystal elastomer oligomer, the liquid crystal elastomer oligomer comprises a liquid crystal unit structural unit and a flexible chain segment, and the polymerization degree of the liquid crystal elastomer oligomer is within the range of 2-100;

extruding a fiber precursor to form a fiber precursor, and drawing the fiber precursor under the action of self gravity to obtain a pre-oriented fiber;

the pre-oriented fibers are cross-linked and cured to obtain liquid crystalline elastomer fibers.

In the first aspect of the embodiment of the application, the polymerization degree of the liquid crystal elastomer oligomer is controlled within the range of 2-100, so that the fiber precursor formed by extrusion can be stretched and oriented under the action of self gravity, the process of setting a stretching device to stretch the fiber precursor and the investment of stretching equipment are reduced, the production process is simplified, the production efficiency is improved, and the production cost is reduced.

In one possible implementation manner of the first aspect of the embodiments of the present application, in the step of providing the fiber precursor, the polymerization degree of the liquid crystal elastomer oligomer is in a range of 3 to 10.

In one possible implementation of the first aspect of the embodiments of the present application, the step of extruding the fiber precursor to form the fiber precursor includes:

heating the fiber precursor to enable the fiber precursor to reach a preset temperature T when being extruded, wherein the value range of the preset temperature T is 20-200 ℃;

preferably, the preset temperature T is in the range of 25-100 ℃.

In one possible embodiment of the first aspect of the examples herein, the step of cross-linking and curing the pre-oriented fibers is characterized by:

and crosslinking and curing the pre-oriented fibers by at least one of a photo-initiated crosslinking mode, an atmosphere-initiated crosslinking mode and a ray-initiated crosslinking mode.

In one possible implementation of the first aspect of the embodiments of the present application, the step of extruding the fiber precursor to form the fiber precursor is characterized by:

extruding a fiber precursor wrapped with a fluid to be dried to obtain a fiber precursor with the fluid to be dried as a central core;

preferably, the method for preparing the liquid crystal elastomer fiber further comprises:

drying the liquid crystal elastomer fiber containing the fluid to be dried to obtain a liquid crystal elastomer hollow fiber having a hollow structure.

In one possible implementation of the first aspect of the embodiments of the present application, in the step of extruding the fiber precursor to form a fiber precursor:

and extruding a plurality of fiber precursors simultaneously to obtain the fiber precursor with a plurality of fiber precursor layers, wherein every two adjacent fiber precursor layers are different from each other.

In one possible embodiment of the first aspect of the examples of the present application, in a process for preparing a liquid crystalline elastomeric fiber,

the extrusion height of the fiber precursor ranges from 1cm to 100 cm;

preferably, the extrusion height of the fiber precursor ranges from 10cm to 40 cm;

preferably, the extrusion height of the fiber precursor ranges from 15cm to 25 cm.

In one possible implementation of the first aspect of the embodiments of the present application, in the step of extruding the fiber precursor to form the fiber precursor,

the shear viscosity of the fiber precursor ranges from 0.1 Pa · s to 100000Pa · s;

preferably, the shear viscosity of the fiber precursor is in the range of 10 to 1000 pas.

In a second aspect of the embodiments of the present application, a liquid crystal elastomer fiber is provided, where the liquid crystal elastomer fiber includes a liquid crystal elastomer oligomer, and a polymerization degree of the liquid crystal elastomer oligomer is in a range of 2 to 100;

preferably, the polymerization degree of the liquid crystal elastomer oligomer is in the range of 4-8;

in a second aspect of the embodiments of the present application, there is provided a liquid crystal elastomer fiber, wherein Tg of the liquid crystal elastomer oligomer is-13.4 ℃, and T of the liquid crystal elastomer oligomer_NI75.8 ℃, Tg of the liquid crystalline elastomer fiber of 1.8 ℃, T of the liquid crystalline elastomer fiber_NIIs 102.8 ℃;

preferably, the liquid crystal elastomer oligomer has a thermal response deformation rate of 25% to 40%.

Drawings

Other features, objects and advantages of the invention will become apparent from the following detailed description of non-limiting embodiments thereof, when read in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof, and which are not to scale.

FIG. 1 is a flow chart of a process for making a liquid crystalline elastomeric fiber in a first aspect of an embodiment of the present application;

FIG. 2 is a flow chart of another method for making a liquid crystalline elastomeric fiber in a first aspect of an embodiment of the present application;

FIG. 3 is a flow chart of yet another method for making a liquid crystal elastomeric fiber in a first aspect of an embodiment of the present application;

FIG. 4 is a diagram of a process for preparing a liquid crystalline elastomeric fiber in a first aspect of an embodiment of the present application;

FIG. 5 is a hydrogen nuclear magnetic resonance spectrum of a liquid crystal elastomer oligomer according to the second aspect of the example of the application;

FIG. 6 is a graph of shear viscosity versus shear rate for liquid crystalline elastomer oligomers at various temperatures in a second aspect of the examples herein;

FIG. 7 is a DSC of an oligomer of a liquid crystal elastomer in a second aspect of the example of the application;

FIG. 8 is a DSC of a liquid crystal elastomer fiber in a second aspect of an embodiment of the present application;

FIG. 9 is a graph showing the repeatability of the thermal response of a liquid crystal elastomer fiber according to the second aspect of the embodiment of the present application;

in the figure:

a fiber precursor reservoir-1; extrusion head-2; a fiber collector-3; a photoinitiator-4;

fiber precursor-L1; pre-oriented fiber-L2; pre-oriented fiber-L2' in a cross-linked cured state; liquid crystal elastomeric fiber-L3; extrusion height-H.

Detailed Description

Features and exemplary embodiments of various aspects of the present invention will be described in detail below, and in order to make objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not to be construed as limiting the invention. It will be apparent to one skilled in the art that the present invention may be practiced without some of these specific details. The following description of the embodiments is merely intended to provide a better understanding of the present invention by illustrating examples of the present invention.

In the process of long-term research, the inventor finds that the general process for preparing the liquid crystal elastomer fiber by adopting the melt extrusion method needs more processing steps and has low preparation efficiency. The general process for obtaining liquid crystalline elastomer fibers by melt extrusion is as follows: the liquid crystal elastomer oligomer is mixed with the crosslinking agent in a molten state, and is extruded and molded by a screw. Stretching the extrudate by a collecting device after extrusion to orient the liquid crystal cells in the extrudate; after extrusion, the orientation of the liquid crystal cells is gradually fixed and the liquid crystal elastomer fiber is obtained after a period of time following the gradual reaction of the oligomer with the crosslinking agent.

The materials required for extrusion in the general melt extrusion method need to be prepared and used at present, and cannot be stored for a long time, so that the preparation process steps are complicated. Higher temperatures and pressures are required for extrusion due to the higher molecular weight of the prepolymer in the material required for extrusion. After the extrudate is formed, a stretching device is additionally arranged to stretch the extrudate in a general extrudate, so that the investment of equipment and the complexity of steps are increased, and the production efficiency is reduced. After obtaining a prefabricated object with fixed pre-orientation of the liquid crystal element structural unit, the reaction and the curing are carried out for a long time, and the liquid crystal elastomer polymer fiber is difficult to obtain quickly.

The present application has been made in view of the discovery and analysis of the above-mentioned technical problems.

As shown in fig. 1, a first aspect of embodiments of the present application provides a method for preparing a liquid crystal elastomer fiber, comprising:

s10, providing a fiber precursor, wherein the fiber precursor comprises at least one liquid crystal elastomer oligomer, the liquid crystal elastomer oligomer comprises liquid crystal elementary structural units and flexible chain segments, and the polymerization degree of the liquid crystal elastomer oligomer is within the range of 2-100;

s20, extruding the fiber precursor to form a fiber precursor, and drawing the fiber precursor under the action of self gravity to obtain pre-oriented fiber;

s30, crosslinking and curing the pre-oriented fiber to obtain the liquid crystal elastomer fiber.

In the first aspect of the embodiment of the application, the polymerization degree of the liquid crystal elastomer oligomer is controlled within the range of 2-100, so that the fiber precursor formed by extrusion can be stretched and oriented under the action of self gravity, the process of setting a stretching device to stretch the fiber precursor and the investment of stretching equipment are reduced, the production process is simplified, the production efficiency is improved, and the production cost is reduced. In the process of continuously extruding the fiber precursor, the fiber precursor is continuously stretched under the action of self gravity to form the fiber precursor. The fiber precursor is crosslinked and solidified in the falling process along the self gravity direction to form the liquid crystal elastomer fiber. In summary, in the process of preparing the liquid crystal elastomer fiber in the first aspect of the embodiment of the present application, the mechanical stretching step is simplified and omitted, and the fiber precursor is stretched to obtain the pre-oriented fiber, and the cross-linking and curing pre-oriented fiber is tightly connected, so that the fiber precursor can be continuously and efficiently prepared to obtain the liquid crystal elastomer fiber, and the production efficiency is greatly improved.

The degree of polymerization refers to the number of times repeating units (or segments) appear in succession in the molecular chain of the polymer. The polymer is composed of a mixture of a group of homologues with different polymerization degrees and structural forms, so that the polymerization degrees are uniformly averaged. In the present application, the polymerization degree refers to the statistical average of the number of occurrences of mesogen structural units in the molecular chain of the liquid crystal elastomer oligomer formed by polymerization.

In some optional embodiments, in the step of providing the fiber precursor S10, the polymerization degree of the liquid crystal elastomer oligomer is in a range of 3-10. Further, in the embodiments, when the polymerization degree of the liquid crystal elastomer oligomer is within the range of 3-10, the fiber precursor has better fluidity and is easier to be extruded and molded, and the fiber precursor formed by extrusion is easier to be stretched and oriented along the gravity direction under the action of the self gravity, so that the liquid crystal elastomer fiber with higher response deformation rate is more favorably formed.

As shown in fig. 2, in some alternative embodiments, the step S20 of extruding the fiber precursor to form the fiber precursor includes:

s21, heating the fiber precursor to enable the fiber precursor to reach a preset temperature T when being extruded, wherein the value range of the preset temperature T is 20-200 ℃.

In some optional embodiments, the preset temperature T ranges from 25 ℃ to 100 ℃.

In the embodiment, the fiber precursor is heated, so that the viscosity of the fiber precursor is increased, the optimized flowability is more beneficial to the extrusion step, the extruded fiber precursor has better continuity and sustainability in the stretching and orientation process, the fiber precursor is prevented from being broken in a segmented manner in the stretching and orientation process, and the length of the subsequently formed liquid crystal elastomer fiber is increased.

In some alternative embodiments, in step S30 of cross-linking the cured pre-oriented fibers:

and crosslinking and curing the pre-oriented fibers by at least one of a photo-initiated crosslinking mode, an atmosphere-initiated crosslinking mode and a ray-initiated crosslinking mode.

In the embodiments, the photo-initiated crosslinking mode, the atmosphere-initiated crosslinking mode and the radiation-initiated crosslinking mode belong to non-contact crosslinking modes, i.e., a crosslinking agent is not required to be added into a fiber precursor, and the pre-oriented fiber is crosslinked after the pre-oriented fiber is formed, so that the time for forming a crosslinking network by the liquid crystal elastic oligomer is shortened, the orientation of a liquid crystal elementary structure unit in the pre-oriented fiber is better fixed, the time consumed in the step of waiting for crosslinking of the pre-taken fiber under the action of the crosslinking agent is avoided, and the production efficiency is improved. Moreover, the non-contact crosslinking mode is adopted to avoid damaging the shape of the extruded pre-oriented fiber, and the shape structure of the liquid crystal elastomer fiber can be better kept.

In some examples of these embodiments, the pre-oriented fibers are cross-linked and cured by photo-induced cross-linking, a photo-initiator is added to the fiber precursor and the liquid crystal elastomer oligomer has a corresponding reactive group (e.g., acrylate group), and the pre-oriented fibers are irradiated with an external light source (e.g., uv light source) in step S30 to induce cross-linking and curing of the pre-oriented fibers.

In other examples of these embodiments, the pre-oriented fibers are cross-linked and cured using an atmosphere-induced cross-linking means. In these examples, the pre-oriented fibers are subjected to an atmosphere containing a catalyst that catalyzes the cross-linking curing to cross-link and cure the pre-oriented fibers.

In another example of these embodiments, the pre-oriented fibers are cross-linked and cured using radiation-induced cross-linking. In one example, the liquid crystal elastomer oligomer in the pre-oriented fiber contains an olefinic bond as a reactive end group, and the irradiation of the pre-oriented fiber with radiation can generate a radical or ion active center in the pre-oriented fiber for initiating the polymerization of the liquid crystal elastomer oligomer, so that the pre-oriented fiber is crosslinked and cured.

In some alternative embodiments, in step S20 of extruding the fiber precursor to form a fiber precursor:

and extruding the fiber precursor wrapped with the fluid to be dried to obtain the fiber precursor with the fluid to be dried as a central core.

In some examples of these embodiments, the drying fluid is water or a readily volatile organic solvent or the like (e.g., ethanol). It is understood that the drying fluid is an organic solvent immiscible with the liquid crystalline elastomer oligomer.

In some examples of these embodiments, the extruded fiber precursor has a low degree of polymerization of the liquid crystal oligomer, good flow properties, and is not subjected to mechanical contact stretching after extrusion, and the fluid to be dried is easily wrapped by the fiber precursor to form a central core of the fiber precursor.

As shown in fig. 3, in some alternative embodiments, the method for preparing a liquid crystal elastomeric fiber further comprises:

and S40, drying the liquid crystal elastomer fiber containing the fluid to be dried to obtain the liquid crystal elastomer hollow fiber with a hollow structure.

In an example of some of the above embodiments, a method for making a liquid crystal elastomeric fiber comprises:

s10, providing a fiber precursor, wherein the fiber precursor comprises at least one liquid crystal elastomer oligomer, the liquid crystal elastomer oligomer comprises liquid crystal elementary structural units and flexible chain segments, and the polymerization degree of the liquid crystal elastomer oligomer is within the range of 2-100.

S20, extruding the fiber precursor wrapped with the fluid to be dried to obtain the fiber precursor with the fluid to be dried as the central core, and drawing the fiber precursor under the action of self gravity to obtain the pre-oriented fiber.

S30, crosslinking and curing the pre-oriented fiber to obtain the liquid crystal elastomer fiber.

And S40, drying the liquid crystal elastomer fiber containing the fluid to be dried to obtain the liquid crystal elastomer hollow fiber with a hollow structure.

In these examples, the degree of polymerization of the fiber precursor within the above selected range provides good flowability, which facilitates extrusion of the fluid to be dried. In step S20, the fiber precursor is stretched under its own weight without being subjected to external mechanical stretching, and the fluid to be dried as the central core is also stretched under its own weight to form a mandrel located on the central axis of the pre-oriented fiber. The liquid crystal elastomer hollow fiber with the hollow structure has wide application prospect in industry.

In some alternative embodiments, in step S20 of extruding the fiber precursor to form a fiber precursor:

and extruding a plurality of fiber precursors simultaneously to obtain the fiber precursor with a plurality of fiber precursor layers, wherein every two adjacent fiber precursor layers are different from each other.

In some examples of these embodiments, a plurality of fiber precursors are configured prior to extrusion. The extrusion operation was carried out using a multi-layer annular extrusion head. Each layer in the multi-layer annular extrusion head corresponds to a different fiber precursor. In these examples, in step S30, a liquid crystal elastomer fiber having a cross section of multiple layers is obtained, and every two adjacent fiber layers in the liquid crystal elastomer fiber are different from each other, that is, the cross-linked networks formed by the liquid crystal elastomer oligomers are different from each other. In actual production, various multilayer fibers can be produced according to application requirements, and the multilayer fibers have a composite structure and integrate the advantages of various different materials.

Fig. 4 shows a process for preparing a liquid crystal elastomer fiber in one example. In this example, the prepared fiber precursor is placed into a fiber precursor reservoir. The fiber precursor storage is connected with the extrusion head, and the fiber precursor storage can heat the fiber precursor so that the shear viscosity of the fiber precursor meets the extrusion requirement.

The extrusion outlet of the extrusion head faces to the horizontal ground, and an initiation crosslinking curing device is arranged below the extrusion head. In this example, the crosslinking curing device is a photoinitiator that provides a light source that initiates crosslinking curing of the pre-oriented fibers.

And extruding the fiber precursor with the shear viscosity reaching a preset value to form the fiber precursor. The cross-sectional radius of the fiber precursor is continuously reduced under the action of the self gravity in the direction from the extrusion head to the fiber collector, and the fiber precursor is extruded by the extrusion head continuously, so that the cross-sectional radius of the fiber precursor is stabilized in a certain range and the fiber precursor is stretched under the action of the self gravity to obtain the pre-oriented fiber. The mesogens in the liquid crystal elastomer oligomer in the pre-oriented fibers are oriented along the gravitational force to which they are subjected.

The degree of orientation of the mesogen in the pre-oriented fiber L2 was optimized, and the degree of orientation of the pre-oriented fiber L2 was substantially the same as the degree of orientation of the finally obtained liquid crystal elastomer fiber. The extrusion height H is positively correlated to the degree of orientation of the pre-oriented fiber L2 for the same fiber precursor and for ensuring uninterrupted flow of the extruded fiber precursor. And (3) crosslinking and curing the pre-oriented fibers by using a photo initiator, and converting the pre-oriented fibers into the pre-oriented fibers in a crosslinking and curing state within the illumination range of the photo initiator. The crosslinked network in the pre-oriented fibers in the crosslinked and cured state is in a step-by-step formation stage.

The pre-oriented fibers in the cross-linked and cured state fall into a fiber collector after the cross-linking and curing are finished, and the liquid crystal elastomer fibers are obtained.

It should be noted that the extrusion height in the present application refers to the distance from the extrusion outlet of the extrusion head to the fiber collector. The height of the pre-oriented fibers in a cross-linked and cured state refers to the height of the pre-oriented fibers in a cross-linking and curing apparatus.

In the example, in the preparation flow of the liquid crystal elastomer fiber, the fiber precursor does not need to be prepared as it is, so that the steps in the actual preparation process are saved. During the process of extruding the fiber precursor to the liquid crystal elastomer fiber, no contact type mechanical processing machine is added, so that the appearance structure of the liquid crystal elastomer fiber is better ensured. The process from the extrusion of the fiber precursor to the collection of the liquid crystal elastomer fiber is continuous without additional processing or a process to be crosslinked, thereby improving the production continuity of the liquid crystal elastomer fiber and the production efficiency of the liquid crystal elastomer fiber.

In some alternative embodiments, in the process for preparing liquid crystalline elastomeric fibers,

the extrusion height of the fiber precursor ranges from 1cm to 100 cm.

In some alternative embodiments, the extrusion height of the fiber precursor ranges from 10cm to 40 cm. In the embodiments, the extrusion height of the fiber precursor ranges from 10cm to 40cm, the thermal response deformation rate of the prepared liquid crystal elastomer fiber is high, and the thermal response deformation rate is between 28% and 40%. The liquid crystal elastomer fiber with high thermal response deformation rate has wide application prospect, and can be used for manufacturing flexible drivers, drivable fabrics, thermal response sensors and the like.

In some alternative embodiments, the extrusion height of the fiber precursor ranges from 15cm to 25 cm. In the embodiments, the extrusion height of the fiber precursor ranges from 15cm to 25cm, and the prepared liquid crystal elastomer fiber has more excellent response deformation rate.

In some alternative embodiments, in the step of extruding the fiber precursor to form the fiber precursor,

the shear viscosity of the fiber precursor ranges from 0.1 Pa · s to 100000Pa · s.

In some optional embodiments, further, the shear viscosity of the fiber precursor ranges from 10 Pa-1000 Pa-s.

In these embodiments, in order to make the fiber precursor easily extruded and have good fluidity, and facilitate the subsequent stretching orientation of the fiber precursor under the action of its own weight, the pre-oriented fiber is continuously formed without flow interruption, and the shear viscosity of the fiber precursor during extrusion needs to be set. In some examples, the shear viscosity of the fiber precursor is adjusted by adjusting the temperature of the fiber precursor during extrusion and/or adding additives to the fiber precursor during extrusion, so that the shear viscosity of the fiber precursor is within the above value range, and the liquid crystal elastomer fiber with more excellent performance is obtained.

In a second aspect of the embodiments of the present application, a liquid crystal elastomer fiber includes a liquid crystal elastomer oligomer, and a polymerization degree of the liquid crystal elastomer oligomer is in a range of 2 to 100.

In these examples, the liquid crystal elastomer fiber has a large deformation rate in thermal response and a good response repetition property.

In some alternative embodiments, the liquid crystal elastomer oligomer has a degree of polymerization in the range of 4 to 8.

In some alternative embodiments, the liquid crystal elastomer oligomer has a Tg of-13.4 ℃ and the liquid crystal elastomer oligomer has a T_NI75.8 ℃, Tg of the liquid crystalline elastomer fiber of 1.8 ℃, T of the liquid crystalline elastomer fiber_NIIt was 102.8 ℃.

In some alternative embodiments, the liquid crystal elastomer oligomer has a rate of thermally responsive deformation of 25% to 40%

The following further illustrates, in specific examples, the method for preparing an elastomeric fiber for night vision provided in the first aspect of the present application and a liquid crystalline elastomeric fiber provided in the second aspect of the present application.

[ detailed description ] embodiments

1. Preparation of liquid crystalline elastomer oligomers

12.0mmol of 1, 4-bis [4'- (3-acryloyloxy-propoxy) -benzoyloxy ] -2-methyl-benzene (RM257, purity 98%) and 9.6mmol of 2, 2' - (1, 2-ethanediylbis-oxo) bisethanethiol (EDDET, purity 99%) were dissolved in 30mL of acetone (purity 99.5%) to obtain a reaction mixture. 1.2mmol of diethylamine (purity 98%) as a catalyst was gradually added dropwise to the reaction mixture obtained above, and the reaction mixture to which the catalyst was added was sealed and stirred overnight to obtain a first reaction solution.

Adding photoinitiator benzoin diethyl ether (IG651 with the purity of 99%) into the first reaction solution, and uniformly mixing to obtain a first mixed solution, wherein the photoinitiator benzoin diethyl ether accounts for 2 wt% of the reaction solution.

Heating the first mixed solution mixed with the photoinitiator to 85 ℃, distilling to remove most of solvent acetone, transferring the first mixed solution into a vacuum oven, and vacuum-drying to remove the residual solvent to obtain the liquid crystal elastomer oligomer containing the photoinitiator. The liquid crystal elastomer oligomer containing the photoinitiator is stored in a dark place at a low temperature before use, and the storage temperature is about 0-8 ℃.

2. Characterization of liquid Crystal elastomer oligomers

The prepared liquid crystal elastomer oligomer is subjected to hydrogen nuclear magnetic resonance detection to obtain a hydrogen nuclear magnetic resonance map of the liquid crystal elastomer oligomer shown in fig. 5.

The polymerization degree of the liquid crystal elastomer oligomer is 5.6-6.0. Further, the polymerization degree of the liquid crystal elastomer oligomer is about 5.8. The liquid crystal elastomer oligomer can be calculated using formula 1:

wherein, I (a), I (b), I (c), I (d) are the integral areas of H corresponding to the letter marks in FIG. 5.

FIG. 6 shows the shear viscosity of liquid crystalline elastomer oligomers at different temperatures as a function of shear rate. As can be seen from fig. 6, in the temperature range of 25 to 85 ℃, the range of change in shear viscosity of the liquid crystal elastomer oligomer decreases as the shear rate increases with an increase in temperature. Under the same shear rate, the higher the temperature, the lower the shear viscosity of the liquid crystal elastomer oligomer, which indicates that the heating treatment of the fiber precursor is beneficial to reducing the shear viscosity of the fiber precursor containing the liquid crystal oligomer, and the fiber precursor has higher fluidity and is beneficial to better stretching orientation of the fiber precursor under the action of self gravity after extrusion.

FIG. 7 shows that the glass transition temperature Tg of the liquid-crystalline elastomer oligomer is-13.4 ℃ and also shows the liquid-crystalline phase-isotropic phase transition temperature T_NIThe temperature of (2) was 75.8 ℃.

The test results of fig. 7 were measured by Differential Scanning Calorimetry (DSC). The specific scanning conditions were: heating to 125 deg.C at 10 deg.C/min, cooling to-35 deg.C, and heating to 125 deg.C at 5 deg.C/min.

3. The preparation process of the liquid crystal elastomer hollow fiber comprises the following steps:

the liquid crystal elastomer oligomer containing the photoinitiator obtained above was put into the loading chamber of the fiber precursor reservoir 1 shown in fig. 4, and the liquid crystal elastomer oligomer containing the photoinitiator was heated so that the temperature of the liquid crystal elastomer oligomer containing the photoinitiator reached 65 ℃. The extruder adopts a double-layer concentric extrusion head, the inner diameter of the extrusion head of the outer layer is 1.1mm, the outer diameter of the extrusion head of the inner layer is 0.7mm, and the inner diameter of the extrusion head of the inner layer is 0.4 mm.

The liquid crystal elastomer oligomer containing the photoinitiator was extruded from the outer layer extrusion head at 65 ℃ by an air pressure of 90psi to form a tube shell shape, while water was extruded from the inner layer extrusion head by a liquid pump to extrude a fiber precursor wrapped with water (the fiber precursor region in this example was the above-mentioned liquid crystal elastomer oligomer containing the photoinitiator) to obtain a fiber precursor having water as a central core.

The fiber precursor with water as the central core body is stretched under the action of self gravity to obtain the pre-oriented fiber.

And (3) crosslinking and curing the pre-oriented fibers by using a photo initiator to obtain the liquid crystal elastomer fibers. Specifically, the photoinitiator comprises two ultraviolet light-gathering LED lamps with the light-emitting wavelength of 365nm, and light spots emitted by the lamps are focused on the pre-oriented fibers falling continuously. In the irradiation area of the photoinitiator, the preset directional fiber is converted into a pre-oriented fiber in a cross-linking and curing state, a liquid crystal elastomer fiber is obtained after the cross-linking and curing are finished, and the liquid crystal elastomer fiber falls into a fiber collector to be collected and stored.

And (3) completely evaporating the water in the core of the liquid crystal elastomer fiber to obtain the liquid crystal elastomer hollow fiber.

4. Characterization and testing process of the liquid crystal elastomer hollow fiber:

FIG. 8 shows that the glass transition temperature Tg of the hollow fibers of the liquid crystalline elastomer is 1.8 ℃ and also shows the liquid crystalline phase-isotropic phase transition temperature T_NIThe temperature of (2) was 102.8 ℃.

The test results of fig. 8 were measured by Differential Scanning Calorimetry (DSC). The specific scanning conditions were: the temperature is raised to 160 ℃ at the speed of 20 ℃/min, the temperature is lowered to-35 ℃, and then the temperature is raised to 160 ℃ at the speed of 10 ℃/min.

Table 1 is a table of diameter and thermal response deformation rate data for liquid crystalline elastomer hollow fibers at different extrusion heights. Specifically, the thermal response deformation rate K in this example satisfies equation 2:

k | L1-Lo |/Lo 100% formula 2,

in formula 2, Lo is the original length of the liquid crystal elastomer hollow fiber at normal temperature, and L1 is the length of the liquid crystal elastomer hollow fiber after shrinkage under 140 ℃ heat treatment.

TABLE 1

As can be seen from Table 1, when the extrusion height is in the range of 10cm to 30cm, the outer diameter and the inner diameter of the liquid-crystalline elastomer hollow fiber obtained by the extrusion height being about high are about small. When the extrusion height is within the range of 10 cm-30 cm, the liquid crystal elastomer hollow fiber has better thermal response deformation rate, and the thermal response deformation rate within the range of 15 cm-25 cm is particularly good.

FIG. 9 shows the results of the liquid crystalline elastomer hollow fiber thermal response repeatability test at an extrusion height of 20 cm. Heating and cooling cycle experiments are carried out 5000 times on the liquid crystal elastomer hollow fiber when the extrusion height is 20cm so as to test the thermal response repeatability of the liquid crystal elastomer hollow fiber. Specifically, the liquid crystal elastomer hollow fiber which is originally at normal temperature is heated to shrink, and then the liquid crystal elastomer hollow fiber which is at high temperature is subjected to reduction treatment to extend and recover the original length. L is the actual length of the liquid crystal elastomer hollow fiber after being heated and shrunk or the actual length of the liquid crystal elastomer hollow fiber after being cooled, and Lo is the original length of the liquid crystal elastomer hollow fiber which is not heated. And L/Lo is the ratio of the actual length of the liquid crystal elastomer hollow fiber to the original length of the liquid crystal elastomer hollow fiber in a temperature rise or temperature fall experiment. Under the most ideal condition, the L/Lo of the liquid crystal elastomer hollow fiber is equal to 0.6 after the liquid crystal elastomer hollow fiber is subjected to a heating experiment; and after the liquid crystal elastomer hollow fiber which is already at a high temperature is subjected to a cooling experiment, the L/Lo of the liquid crystal elastomer hollow fiber is equal to 1.0. If the number of times of the cycle test is more, and the L/Lo can reach 0.6 during heating in each cycle test, and the L/Lo is equal to 1.0 after temperature reduction, the thermal response repeatability of the liquid crystal elastomer hollow fiber is better. Therefore, the liquid crystal elastomer hollow fiber in the embodiment has excellent thermal response repeatability, and the ratio of L/Lo is kept stable after heating and cooling cycle test of about 5000 times.

The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. For example, the algorithms described in the specific embodiments may be modified without departing from the basic spirit of the invention. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.