CN113603919A

CN113603919A - Method for orienting, patterning, repairing, removing, welding polymeric materials

Info

Publication number: CN113603919A
Application number: CN202110926925.9A
Authority: CN
Inventors: 吉岩; 姚艳锦
Original assignee: Tsinghua University
Current assignee: Tsinghua University
Priority date: 2021-08-12
Filing date: 2021-08-12
Publication date: 2021-11-05
Anticipated expiration: 2041-08-12
Also published as: CN113603919B

Abstract

A method for orienting, patterning, repairing, removing, welding a polymeric material comprising dynamic covalent bonds and having a cross-linked network structure is provided. The orientation processing method comprises the following steps: s10, enabling at least part of molecular chains in the cross-linked network structure of the polymer material to be oriented along a preset direction; s20, contacting the polymer material with a catalyst capable of catalyzing the exchange reaction of dynamic covalent bonds in a swelling state in a solvent, so as to exchange the dynamic covalent bonds, thereby forming a new cross-linked network structure, wherein the catalyst capable of catalyzing the exchange reaction of dynamic covalent bonds is dissolved in the solvent. The catalyst is dissolved in a solvent, so that the polymer material can be swelled at room temperature and the dynamic covalent bond can be subjected to exchange reaction, and the process difficulty and the production cost are reduced. The method is simple, easy to operate and has general advantages.

Description

Method for orienting, patterning, repairing, removing, welding polymeric materials

Technical Field

The application relates to the field of polymer materials, in particular to a method for carrying out orientation processing, patterning processing, repairing, removing and welding on a polymer material.

Background

Liquid Crystal Elastomer (LCE) is an important soft driving material, and its three-dimensional dynamic structure plays an important role in practical applications, for example, it can be used as soft robot, flexible wearable material, etc. However, the planar sheet or film-like structure of the liquid crystal elastomer is easier to mass-produce, store, package, and transport than the three-dimensional dynamic structure of the liquid crystal elastomer. Therefore, it is important to reversibly convert a flat sheet or film-like structure of a liquid crystal elastomer into a three-dimensional dynamic structure directly by shape editing.

The traditional polymer forming method adopts a hot forming method, but the hot forming method generally needs a mold, and the difficulty of polymer demoulding often limits the complexity of the structure of the obtained polymer. Therefore, designing a simple and feasible processing method capable of effectively controlling the three-dimensional dynamic structure of the liquid crystal elastomer becomes a hotspot of research in the field.

Disclosure of Invention

The present application provides a method for orienting, patterning, repairing, removing, welding polymeric materials to solve the problems of the prior art.

The present application provides in a first aspect a method for orienting a polymeric material comprising dynamic covalent bonds and having a cross-linked network structure, the method comprising the steps of: s10, enabling at least part of molecular chains in the cross-linked network structure of the polymer material to be oriented along a preset direction; s20, contacting the polymer material with a catalyst capable of catalyzing the exchange reaction of dynamic covalent bonds in a swelling state in a solvent, so as to exchange the dynamic covalent bonds, thereby forming a new cross-linked network structure, wherein the catalyst capable of catalyzing the exchange reaction of dynamic covalent bonds is dissolved in the solvent.

In any embodiment herein, the dynamic covalent bond comprises a dynamic interesterified covalent bond.

In any embodiment of the present application, the polymer material is a liquid crystal elastomer material or a non-liquid crystal glass polymer material.

Preferably, the liquid crystal elastomer material is an epoxy liquid crystal elastomer material,

preferably, the non-liquid crystal glass polymer material is an epoxy elastomer material.

In any embodiment of the present application, in step S10, the method of orienting at least a part of molecular chains in a cross-linked network structure of the polymer material in a predetermined direction includes: and performing pre-stretching treatment on the liquid crystal elastomer material.

In any embodiment of the present application, in step S10, the method of orienting at least a part of molecular chains in a cross-linked network structure of the polymer material in a predetermined direction includes: and performing pre-shaping treatment on the non-liquid crystal system glass polymer material.

In any embodiment herein, the solvent comprises one or more of dichloromethane, chloroform, tetrahydrofuran.

In any embodiment herein, the catalyst is a basic catalyst. Preferably, the basic catalyst comprises one or more of 1,5, 7-triazabicyclo [4.4.0] dec-5-ene, zinc acetate, palladium triphenylphosphine.

In any embodiment herein, a catalyst capable of catalyzing a dynamic covalent bond exchange reaction is dissolved in a solvent to form a catalyst solution, and the concentration of the catalyst solution is 0.0005g/ml to 0.1 g/ml.

In any embodiment herein, the swelling temperature is from 15 ℃ to 100 ℃.

A second aspect of the present application provides a method for patterning a polymeric material comprising dynamic covalent bonds and having a cross-linked network structure, the method comprising the steps of: s100, enabling at least part of molecular chains in a cross-linked network structure of the polymer material to be oriented along a preset direction; s200, contacting the polymer material with a catalyst capable of catalyzing dynamic covalent bond exchange reaction in a swelling state in a solvent so as to enable the dynamic covalent bond to perform exchange reaction, thereby forming a new cross-linked network structure and further enabling the polymer material to have different patterns, wherein the catalyst capable of catalyzing dynamic covalent bond exchange reaction is dissolved in the solvent.

In a third aspect, the present application provides a method for repairing a polymeric material comprising dynamic covalent bonds and having a cross-linked network structure, the method comprising the steps of: and contacting the damaged part to be repaired of the polymer material with a catalyst capable of catalyzing dynamic covalent bond exchange reaction in a solvent in a swelling state so as to enable the dynamic covalent bond to perform exchange reaction, thereby forming a new cross-linked network structure on the damaged part to be repaired to realize repair, wherein the catalyst capable of catalyzing dynamic covalent bond exchange reaction is dissolved in the solvent.

In a fourth aspect of the present application, there is provided a method for scavenging a polymeric material comprising dynamic covalent bonds and having a cross-linked network structure, the method comprising the steps of: and contacting the part to be eliminated of the polymer material with a catalyst capable of catalyzing dynamic covalent bond exchange reaction in a swelling state in a solvent so as to enable the dynamic covalent bond exchange reaction to occur and further eliminate the part to be eliminated, wherein the catalyst capable of catalyzing the dynamic covalent bond exchange reaction is dissolved in the solvent.

A fifth aspect of the present application provides a method for welding a polymeric material comprising dynamic covalent bonds and having a cross-linked network structure, the method comprising the steps of: the polymer material is divided into at least two components with the same or different types, at least one contact part between every two adjacent components of the polymer material is contacted with a catalyst capable of catalyzing the exchange reaction of dynamic covalent bonds in a state that the polymer material is swelled in a solvent, so that the dynamic covalent bonds are subjected to the exchange reaction, and a new cross-linked network structure is formed to realize the welding fixation of the polymer material, wherein the catalyst capable of catalyzing the exchange reaction of dynamic covalent bonds is dissolved in the solvent.

The application has at least the following beneficial effects:

the catalyst is dissolved in a solvent, so that the polymer material can be swelled at room temperature and the dynamic covalent bond can be subjected to exchange reaction, and the process difficulty and the production cost are reduced.

The method is simple, easy to operate and universal, and can be used for realizing the single-domain orientation processing of the liquid crystal elastomer and the shaping processing of the non-liquid crystal system glass polymer material.

The method of the present application can directly and reversibly edit a two-dimensional structure of a liquid crystal elastomer material into a three-dimensional dynamic structure having a complex pattern by selectively coating an appropriate amount of a solvent containing a catalyst on the liquid crystal elastomer material without using a mold.

The method can realize the mechanical processing and batch production preparation of the three-dimensional dynamic structure of the liquid crystal elastomer material with different requirements and various complex patterns.

The method can realize the mechanized processing and the mass production preparation of the three-dimensional structure of the non-liquid crystal system glass polymer material with different requirements and various complex patterns.

The method can realize batch repair, cleaning and welding processes of the liquid crystal elastomer material and the non-liquid crystal system glass polymer material, and can realize in-situ welding on the premise of not moving a welding body and break the limitation of space during welding.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments of the present application will be briefly described below, and it is obvious that the drawings described below are only some embodiments of the present application, and it is obvious for a person skilled in the art to obtain other drawings based on the drawings without any creative effort.

Fig. 1 is a schematic view of the alignment process of a liquid crystal elastomer material according to an embodiment of the present application.

Fig. 2 is a schematic diagram of spontaneous reversible stretching deformation of a monodomain aligned liquid crystal elastomer material of an embodiment of the present application under heating.

Fig. 3 is a schematic view of a liquid crystal elastomer material patterning process according to an embodiment of the present application.

Fig. 4 is a schematic illustration of scratch repair of a polymer material according to an embodiment of the present application.

FIG. 5 is a schematic view of a weld of polymeric materials according to an embodiment of the present application.

FIG. 6 is a schematic view of hole repair in a polymer material according to another embodiment of the present application.

Detailed Description

In order to make the purpose, technical solution and advantageous technical effects of the present invention clearer, the present invention is further described in detail with reference to the following embodiments. It should be understood that the embodiments described in this specification are only for the purpose of explaining the present application and are not intended to limit the present application.

For the sake of brevity, only some numerical ranges are explicitly disclosed herein. However, any lower limit may be combined with any upper limit to form ranges not explicitly recited; and any lower limit may be combined with any other lower limit to form a range not explicitly recited, and similarly any upper limit may be combined with any other upper limit to form a range not explicitly recited. Also, although not explicitly recited, each point or individual value between endpoints of a range is encompassed within the range. Thus, each point or individual value can form a range not explicitly recited as its own lower or upper limit in combination with any other point or individual value or in combination with other lower or upper limits.

In the description herein, it is to be noted that, unless otherwise specified, "above" and "below" are inclusive, and "a plurality" of "one or more" and "one or more" means two or more.

The above summary of the present application is not intended to describe each disclosed embodiment or every implementation of the present application. The following description more particularly exemplifies illustrative embodiments. At various points throughout this application, guidance is provided through a list of embodiments that can be used in various combinations. In various embodiments, the lists are provided as representative groups and should not be construed as exhaustive.

A first aspect of the present application provides a method for orientating a polymeric material comprising a cross-linked network structure of dynamic covalent bonds, the method comprising the steps of: s10, enabling at least part of molecular chains in the cross-linked network structure of the polymer material to be oriented along a preset direction; s20, contacting the polymer material with a catalyst capable of catalyzing the exchange reaction of dynamic covalent bonds in a swelling state in a solvent, so as to exchange the dynamic covalent bonds, thereby forming a new cross-linked network structure, wherein the catalyst capable of catalyzing the exchange reaction of dynamic covalent bonds is dissolved in the solvent.

Dynamic covalent bonds are a class of reversible covalent bonds that can break and recombine under certain environmental conditions (e.g., temperature, pH, light, etc.) and reach thermodynamic equilibrium, which is also known as the exchange reaction of dynamic covalent bonds. The catalyst which can catalyze the exchange reaction of the dynamic covalent bonds is dissolved in the solvent and swells the pre-oriented molecular chains in the polymer material, so that the dynamic covalent bonds in the polymer material can be subjected to the exchange reaction, a new cross-linked network is formed, and the orientation processing method is simple and easy to operate.

In the prior art, a catalyst is usually loaded in a polymer material, and the exchange reaction of a dynamic covalent bond can be carried out under the condition of high-temperature heating, but the catalyst is dissolved in a solvent, so that the polymer material can be swelled and the dynamic covalent bond can be subjected to the exchange reaction in a lower temperature environment even a room temperature environment (for example, 15-35 ℃), and the process difficulty and the production cost are greatly reduced.

The catalyst is dissolved in the solvent to swell the polymer material, and the fixed-point orientation processing of the polymer material can be realized.

In some embodiments, the site of the solvent swelling treatment may be a part or the entirety of the polymeric material.

In some embodiments, the polymeric material may be in the shape of a block, cylinder, column, or sheet. The sheet-like shape may preferably be a sheet-like shape or a film-like shape.

In some embodiments, the dynamic covalent bond can comprise a dynamic interesterified covalent bond.

In some embodiments, the polymer material may be a liquid crystal elastomer material or a non-liquid crystal system glass-like polymer material. Wherein the liquid crystal elastomer material may or may not contain a catalyst. The non-liquid crystal glass polymer material may or may not contain a catalyst. When the liquid crystal elastomer material and the non-liquid crystal glass polymer material contain a catalyst, the speed of the dynamic covalent bond exchange reaction can be increased.

Preferably, the liquid crystal elastomer material may be an epoxy liquid crystal elastomer material.

Preferably, the non-liquid crystal glass polymer material may be a non-liquid crystal epoxy elastomer material.

In some embodiments, in step S10, a part of the molecular chains in the cross-linked network structure of the polymer material may be oriented in a predetermined direction, or all of the molecular chains in the cross-linked network structure of the polymer material may be oriented in a predetermined direction, which may be selected by one skilled in the art according to actual needs.

Referring to fig. 1, in some embodiments, in step S10, the method of orienting at least a portion of molecular chains in a cross-linked network structure of the polymer material in a predetermined direction includes: and performing pre-stretching treatment on the liquid crystal elastomer material. Preferably, the pre-stretching treatment temperature is higher than the glass transition temperature (Tg) of the liquid crystalline elastomeric material. When the pre-stretching treatment temperature is higher than the glass transition temperature of the liquid crystal elastomer material, the liquid crystal elastomer material becomes soft and is easier to stretch and shape. The degree of pre-stretching of the liquid crystal elastomer material is also not particularly limited, and it may be stretched to the maximum. For example, the liquid crystal elastomer material is pre-stretched to an elongation of 80% to 200%.

The liquid crystal elastomer material in the general meaning is a multi-domain liquid crystal elastomer material, liquid crystal elements in the multi-domain liquid crystal elastomer material are not macroscopically and integrally arranged and oriented, and tiny deformation generated when the liquid crystal elements are transformed from a liquid crystal phase to an isotropic phase is random, so that the shape of the whole sample cannot be macroscopically changed. The single-domain liquid crystal elastomer material is characterized in that all liquid crystal elements in the liquid crystal elastomer material are basically oriented and arranged along a specific direction, after the liquid crystal elements are oriented and arranged, when liquid crystal phase-isotropic phase transformation occurs, the liquid crystal elements are switched between order and disorder, and the generated micro deformation can be macroscopically embodied on the whole sample because the directions are basically the same. Therefore, the monodomain liquid crystal elastomer material may have spontaneous reversible deformation. The spontaneous reversible deformation refers to that the sensor can spontaneously respond after sensing external stimulation, and can spontaneously return to a state before responding after the external stimulation is eliminated. In the method, after the liquid crystal elastomer material is subjected to pre-stretching treatment, the orientation state is changed from disorder to order, and after the liquid crystal elastomer material is subjected to solvent swelling treatment and dynamic covalent bonds are subjected to exchange reaction, the orientation of the liquid crystal elastomer material is fixed, so that the single-domain oriented liquid crystal elastomer material can be finally obtained. Referring to fig. 2, the monodomain aligned liquid crystal elastomer material may realize spontaneous reversible stretching deformation under heating. For example, when the heating temperature is lower than the liquid crystal phase transition temperature (Ti) of the monodomain aligned liquid crystal elastomer material, the shape of the monodomain aligned liquid crystal elastomer material remains unchanged; when the heating temperature is equal to or higher than the liquid crystal phase transition temperature (Ti) of the monodomain aligned liquid crystal elastomer material, the monodomain aligned liquid crystal elastomer material may shrink to an initial form (i.e., a form before the pre-stretching treatment).

In some embodiments, in step S10, the method of orienting at least a portion of molecular chains in the cross-linked network structure of the polymer material in a predetermined direction further includes: and performing pre-shaping treatment on the non-liquid crystal system glass polymer material. The pre-shaping treatment is not particularly limited, and may include one or more of stretching treatment, bending treatment, and twisting treatment. When the non-liquid crystal system glass polymer material is subjected to pre-shaping treatment, external force can be used. The non-liquid crystal glass polymer material has a cross-linked network, can not be dissolved or melted at normal temperature like thermosetting resin, but dynamic covalent bonds contained in the non-liquid crystal glass polymer material can be subjected to topological structure recombination under certain stimulation, chemical bonds and cross-linking density are kept basically unchanged, the original cross-linking density is kept, the non-liquid crystal glass polymer material also has the fluidity similar to thermoplastic resin, and the re-shaping processing is realized. After the non-liquid crystal system glass polymer material subjected to the pre-shaping treatment is subjected to subsequent solvent swelling treatment and the exchange reaction of the dynamic covalent bonds, the orientation of the pre-shaped glass polymer material can be kept fixed, and the re-shaping processing of the non-liquid crystal system glass polymer material is realized.

Therefore, the orientation processing method has general advantages, can realize the single-domain orientation processing of the liquid crystal elastomer and can also realize the shaping processing of the non-liquid crystal system glass polymer material.

The solvent can activate the exchange reaction of the catalyst and the dynamic covalent bond, so that the dynamic covalent bond in the polymer material is broken and recombined. In some embodiments, the solvent may include one or more of dichloromethane, trichloromethane, Tetrahydrofuran (THF).

In some embodiments, the catalyst may be a basic catalyst. Preferably, the basic catalyst may comprise one or more of 1,5, 7-triazabicyclo [4.4.0] dec-5-ene (TBD), zinc acetate, palladium triphenylphosphine.

The catalyst capable of catalyzing the dynamic covalent bond exchange reaction is dissolved in the solvent to form a catalyst solution, and the concentration of the catalyst solution is not particularly limited, and may be appropriately adjusted according to the type of the solvent and the desired effect. In some embodiments, preferably, the concentration of the catalyst solution may be 0.0005g/ml to 0.1 g/ml.

In some embodiments, the temperature of swelling in step S20 may be 15 ℃ to 100 ℃. For example, the temperature of swelling may be 15 ℃ to 80 ℃, 15 ℃ to 60 ℃, 15 ℃ to 45 ℃, or 15 ℃ to 35 ℃ (i.e., room temperature).

In some embodiments, the swelling time in step S20 is not particularly limited, and may be determined according to the desired swelling effect. For example, swelling to the point where the polymeric material is completely transparent or swelling to the point where the volume of the polymeric material reaches saturation. Preferably, the swelling time is 1h or less.

In some embodiments, the manner in which the solvent is allowed to swell the polymeric material is not particularly limited. For example, one or more of manual dispensing, dispenser dispensing, stamp stamping, spin coating may be included. Referring to fig. 1, the solvent swells the polymer material by manual dispensing.

In some embodiments, the method for orienting a polymeric material comprising a cross-linked network structure of dynamic covalent bonds may further comprise the steps of: and S30, drying to remove the solvent. The method for drying and removing the solvent is not particularly limited, and the solvent may be naturally evaporated to dryness, or the solvent may be slightly heated to accelerate the volatilization of the solvent. The presence of the solvent causes the dynamic covalent bonds in the polymeric material to continue to exchange, resulting in the formation of a new crosslinked network structure that is not well anchored.

In some embodiments, the sequence of step S10 and step S20 may be reversed, and one skilled in the art may make the selection according to actual circumstances. For example, step S10 may be performed first, and then step S20 may be performed, that is, at least a part of molecular chains in the cross-linked network structure of the polymer material are oriented along a predetermined direction, and then the pre-oriented molecular chains in the polymer material are contacted with a catalyst capable of catalyzing the dynamic covalent bond exchange reaction in a state of being swollen in a solvent; step S20 may be performed first, and then step S10 may be performed, that is, the polymer material is contacted with the catalyst capable of catalyzing the dynamic covalent bond exchange reaction in the state of being swelled in the solvent, and then at least a part of the molecular chains in the crosslinked network structure of the polymer material is oriented in the predetermined direction.

A second aspect of the present application provides a method for patterning a polymeric material comprising a cross-linked network of dynamic covalent bonds, the method comprising the steps of: s100, enabling at least part of molecular chains in a cross-linked network structure of the polymer material to be oriented along a preset direction; s200, contacting the polymer material with a catalyst capable of catalyzing dynamic covalent bond exchange reaction in a swelling state in a solvent so as to enable the dynamic covalent bond to perform exchange reaction, thereby forming a new cross-linked network structure and further enabling the polymer material to have different patterns, wherein the catalyst capable of catalyzing dynamic covalent bond exchange reaction is dissolved in the solvent.

In some embodiments, the site of the solvent swelling treatment may be a part or the entirety of the polymeric material. Referring to fig. 3, the solvent swelling treatment site is a part of the polymer material.

In some embodiments, in step S100, the method of orienting at least a part of molecular chains in the crosslinked network structure of the polymer material in a predetermined direction includes: and performing pre-stretching treatment on the liquid crystal elastomer material. Preferably, the pre-stretching treatment temperature is higher than the glass transition temperature (Tg) of the liquid crystalline elastomeric material. The degree of pre-stretching of the liquid crystal elastomer material is also not particularly limited, and it may be stretched to the maximum. For example, the liquid crystal elastomer material is pre-stretched to an elongation of 80% to 200%. The orientation degree of the pre-stretched part of the liquid crystal elastomer material is different from that of the part which is not pre-stretched, and the pre-stretched part is subjected to solvent swelling treatment and exchange reaction of dynamic covalent bonds to realize orientation fixation, so that the liquid crystal elastomer material can have a three-dimensional dynamic structure.

Referring to fig. 3, the present application enables a two-dimensional structure of a liquid crystal elastomer material to be directly and reversibly edited into a three-dimensional dynamic structure having a complex pattern without the aid of a mold by selectively coating an appropriate amount of a solvent containing a catalyst on a pre-stretched liquid crystal elastomer material. The patterning processing method can realize mechanical processing and batch production preparation of three-dimensional dynamic structures of liquid crystal elastomer materials with different requirements and various complex patterns.

In some embodiments, in step S100, the method of orienting at least a part of molecular chains in the crosslinked network structure of the polymer material in a predetermined direction further includes: and performing pre-shaping treatment on the non-liquid crystal system glass polymer material. The pre-shaping treatment is not particularly limited, and may include one or more of stretching treatment, bending treatment, and twisting treatment. When the non-liquid crystal system glass polymer material is subjected to pre-shaping treatment, external force can be used. The pre-shaping treatment aims to enable the non-liquid crystal glass polymer material to form a required three-dimensional structure under the action of external force, and then the three-dimensional structure of the non-liquid crystal glass polymer material is fixed through solvent swelling treatment and dynamic covalent bond exchange reaction.

Therefore, the patterning processing method has general advantages, and can be used for processing the three-dimensional dynamic structure of the liquid crystal elastomer material and the three-dimensional structure of the non-liquid crystal system glass polymer material.

The catalyst capable of catalyzing the dynamic covalent bond exchange reaction is dissolved in the solvent to form a catalyst solution, the concentration of the catalyst solution is not particularly limited, and the catalyst solution can be appropriately prepared according to the difference of the types of the solvents and the difference of the required effect. In some embodiments, preferably, the concentration of the catalyst solution may be 0.0005g/ml to 0.1 g/ml.

In some embodiments, the temperature of swelling may be 15 ℃ to 100 ℃ in step S200. For example, the temperature of swelling may be 15 ℃ to 80 ℃, 15 ℃ to 60 ℃, 15 ℃ to 45 ℃, or 15 ℃ to 35 ℃ (i.e., room temperature).

In some embodiments, in step S200, the swelling time is not particularly limited and may be determined according to the desired swelling effect. For example, swelling to the point where the polymeric material is completely transparent or swelling to the point where the volume of the polymeric material reaches saturation. Preferably, the swelling time is 1h or less.

In some embodiments, the manner in which the solvent is allowed to swell the polymeric material is not particularly limited. For example, one or more of manual dispensing, dispenser dispensing, stamp stamping, spin coating may be included.

In some embodiments, the method for patterning a polymeric material comprising a crosslinked network structure of dynamic covalent bonds may further comprise the steps of: and S300, drying to remove the solvent. The method for drying and removing the solvent is not particularly limited, and the solvent may be naturally evaporated to dryness, or the solvent may be slightly heated to accelerate the volatilization of the solvent. The presence of the solvent causes the dynamic covalent bonds in the polymeric material to continue to exchange, resulting in the formation of a new crosslinked network structure and a less well-defined pattern of the polymeric material.

A third aspect of the present application provides a method for repairing a polymeric material comprising a cross-linked network of dynamic covalent bonds, the method comprising the steps of: and contacting the damaged part to be repaired of the polymer material with a catalyst capable of catalyzing dynamic covalent bond exchange reaction in a solvent in a swelling state so as to enable the dynamic covalent bond to perform exchange reaction, thereby forming a new cross-linked network structure on the damaged part to be repaired to realize repair, wherein the catalyst capable of catalyzing dynamic covalent bond exchange reaction is dissolved in the solvent.

In some embodiments, the damage may include one or more of scratches, microcracks, holes.

In some embodiments, the polymer material may be a liquid crystal elastomer material or a non-liquid crystal system glass-like polymer material. Wherein, the liquid crystal elastomer material can be a single-domain or multi-domain liquid crystal elastomer material. The liquid crystal elastomer material may or may not contain a catalyst. The non-liquid crystal glass polymer material may or may not contain a catalyst. When the liquid crystal elastomer material and the non-liquid crystal glass polymer material contain a catalyst, the speed of the dynamic covalent bond exchange reaction can be increased.

In some embodiments, the temperature of swelling may be from 15 ℃ to 100 ℃. For example, the temperature of swelling may be 15 ℃ to 80 ℃, 15 ℃ to 60 ℃, 15 ℃ to 45 ℃, or 15 ℃ to 35 ℃ (i.e., room temperature).

In some embodiments, the time of swelling is not particularly limited and may be determined according to the desired swelling effect. For example, swelling to the point where the polymeric material is completely transparent or swelling to the point where the volume of the polymeric material reaches saturation. Preferably, the swelling time is 1h or less.

In some embodiments, the method for repairing a polymeric material comprising a crosslinked network structure of dynamic covalent bonds may further comprise the steps of: the solvent was removed by drying. The existence of the solvent can enable dynamic covalent bonds in the polymer material to continuously carry out exchange reaction, so that a formed new cross-linked network structure cannot be well fixed, and the repair effect of the polymer material is influenced.

The method for drying and removing the solvent is not particularly limited, and the solvent may be naturally evaporated to dryness, or the solvent may be slightly heated to accelerate the volatilization of the solvent.

A fourth aspect of the present application provides a method for scavenging a polymeric material comprising a cross-linked network of dynamic covalent bonds, said method comprising the steps of: and contacting the part to be eliminated of the polymer material with a catalyst capable of catalyzing dynamic covalent bond exchange reaction in a swelling state in a solvent so as to enable the dynamic covalent bond exchange reaction to occur and further eliminate the part to be eliminated, wherein the catalyst capable of catalyzing the dynamic covalent bond exchange reaction is dissolved in the solvent.

In some embodiments, the dissolution temperature may be from 15 ℃ to 100 ℃. For example, the temperature of dissolution may be 15 ℃ to 80 ℃, 15 ℃ to 60 ℃, 15 ℃ to 45 ℃, or 15 ℃ to 35 ℃ (i.e., room temperature).

The catalyst that catalyzes the dynamic covalent bond exchange reaction is dissolved in the solvent to form a catalyst solution, and the concentration of the catalyst is not particularly limited as long as the polymer can be completely dissolved. In some embodiments, preferably, the concentration of the catalyst may be 0.01g/ml to 0.5 g/ml.

In some embodiments, the portion of the polymeric material to be cleaned may be soaked in the solvent.

A fifth aspect of the present application provides a method for welding a polymer material comprising a cross-linked network structure of dynamic covalent bonds, the method comprising the steps of:

the polymer material is divided into at least two components with the same or different types, at least one contact part between every two adjacent components of the polymer material is contacted with a catalyst capable of catalyzing the exchange reaction of dynamic covalent bonds in a state that the polymer material is swelled in a solvent, so that the dynamic covalent bonds are subjected to the exchange reaction, and a new cross-linked network structure is formed to realize the welding fixation of the polymer material, wherein the catalyst capable of catalyzing the exchange reaction of dynamic covalent bonds is dissolved in the solvent.

The welding method is suitable for welding the same or different liquid crystal elastomer materials, the same or different non-liquid crystal system glass polymer materials and the liquid crystal elastomer materials and the non-liquid crystal system glass polymer materials.

The method can realize in-situ welding on the premise of not moving the welding body, and breaks the limitation of space during welding. According to the welding method, the catalyst is dissolved in the solvent to swell the part to be welded, and fixed-point welding of the polymer material can be realized.

In some embodiments, the method for welding a polymer material comprising a cross-linked network structure of dynamic covalent bonds may further comprise the steps of: the solvent was removed by drying. The existence of the solvent can enable dynamic covalent bonds in the polymer material to continuously carry out exchange reaction, so that a formed new cross-linked network structure cannot be well fixed, and the welding effect is influenced. The method for drying and removing the solvent is not particularly limited, and the solvent may be naturally evaporated to dryness, or the solvent may be slightly heated to accelerate the volatilization of the solvent.

In some embodiments, the method for welding a polymer material comprising a cross-linked network structure of dynamic covalent bonds may further comprise the steps of: and applying external force to make at least one contact part between every two adjacent parts of the polymer material contact with a catalyst capable of catalyzing dynamic covalent bond exchange reaction in a state that the contact part is swelled in a solvent, so that the welding of the polymer material is firmer.

The welding method using the polymer material can also repair holes in the polymer material. The method specifically comprises the following steps: cutting a sheet material with the area larger than the diameter of the holes from another polymer material, then covering the sheet material on the holes of the polymer material, and enabling the contact part of the sheet material and the holes to be in contact with a catalyst capable of catalyzing the exchange reaction of dynamic covalent bonds under the state of swelling in a solvent, so that the dynamic covalent bonds are subjected to the exchange reaction, and a new cross-linked network structure is formed to realize the welding fixation of the sheet material and the polymer material, thereby completing the repair of the holes in the polymer material.

The present application is further illustrated below with reference to examples. It is to be understood that these examples are for illustrative purposes only, as various modifications and changes in light thereof will be apparent to those skilled in the art from this disclosure. Unless otherwise indicated, all parts, percentages, and ratios reported in the following examples are on a weight basis, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further treatment, and the equipment used in the examples is commercially available.

Example 1

(1) Preparation of multidomain liquid crystal elastomer sample

A mixture of 0.298g (1mmol) of epoxy mesogen p-biphenyldiol diglycidyl ether (DGE-DHBP) and 0.202g (1mmol) of sebacic acid was placed in a petri dish covered with a Polytetrafluoroethylene (PTFE) film, melted in a heating mantle at 180 ℃ and mixed well with gentle stirring. Then 13.9mg (0.1mmol) of 1,5, 7-triazabicyclo [4.4.0] dec-5-ene (TBD) is added and stirred to uniformly mix the mixture, and when the viscosity of the reaction system is increased but the reaction system does not react until the solid can still be drawn, the reaction system is taken out and slightly cooled to obtain the prepolymer. And (3) placing the prepolymer in two layers of Polytetrafluoroethylene (PTFE) films, using tinfoil as a gasket to control the thickness of the prepolymer film, then carrying out hot pressing and curing on the prepolymer in a tablet press for 6 hours at the temperature of 180 ℃ under the pressure of 6MPa to obtain a liquid crystal elastomer (xLCE) sample sheet with the target thickness, wherein the obtained xLCE sample sheet is a multi-domain epoxy liquid crystal elastomer material.

(2) Single domain orientation processing of multi-domain liquid crystal elastomer sample

And cutting the prepared multi-domain epoxy liquid crystal elastomer sample into a rectangular sample strip, fixing two ends of the rectangular sample strip, then placing the rectangular sample strip on a hot table for heating until the temperature is higher than the glass transition temperature of the epoxy liquid crystal elastomer material, and stretching the rectangular sample strip in a single direction along the length direction until the elongation is about 100%.

1,5, 7-triazabicyclo [4.4.0] dec-5-ene is dissolved in dichloromethane to prepare a catalyst solution, wherein the concentration of 1,5, 7-triazabicyclo [4.4.0] dec-5-ene in the solution is 0.005 g/ml.

And (3) dripping the catalyst solution on the pre-stretched rectangular sample strip at room temperature to enable the pre-stretched rectangular sample strip to be in contact with the catalyst in a swelling state, so that the dynamic ester exchange covalent bonds in the rectangular sample strip are subjected to exchange reaction to form a new cross-linked network structure, and the orientation of the rectangular sample strip is fixed.

After the solvent in the catalyst solution is naturally evaporated to dryness, the rectangular sample strip with fixed orientation is placed on a hot table for heating, and referring to fig. 2, the rectangular sample strip can generate a reversible expansion phenomenon at the liquid crystal phase transition temperature (Ti) of the epoxy liquid crystal elastomer material. When the heating temperature is lower than the liquid crystal phase transition temperature (Ti) of the epoxy liquid crystal elastomer material, the shape of the rectangular sample strip is kept unchanged; when the heating temperature is higher than or equal to the liquid crystal phase transition temperature (Ti) of the epoxy liquid crystal elastomer material, the rectangular sample strip can shrink.

(3) Patterning process for multi-domain liquid crystal elastomer sample

Referring to fig. 3, a pentagram is drawn on a pre-stretched rectangular sample strip in a room temperature environment, and then the pentagram part is swollen with a catalyst solution, so that the pre-stretched rectangular sample strip is contacted with the catalyst in a swollen state, so that the dynamic ester exchange covalent bonds in the rectangular sample strip are subjected to an exchange reaction to form a new cross-linked network structure and fix the orientation. And after the solvent in the catalyst solution is naturally evaporated to dryness, obtaining a sample with only the pentagram area partially oriented on the rectangular sample strip.

(4) Repair of multidomain liquid crystal elastomer sample

Referring to fig. 4, a plurality of scratches are carved on the prepared multi-domain epoxy liquid crystal elastomer sample by a small knife.

And (3) placing the multi-domain epoxy liquid crystal elastomer sample in a catalyst solution at room temperature, taking out the multi-domain epoxy liquid crystal elastomer sample after a period of time, and observing to ensure that scratches on the surface of the multi-domain epoxy liquid crystal elastomer sample disappear.

(5) Welding process of multi-domain liquid crystal elastomer sample

And (3) placing two prepared multi-domain epoxy liquid crystal elastomer sample sheets in a catalyst solution at room temperature, and taking out the sample sheets by using tweezers when the sample sheets are swelled from white to be completely transparent. Referring to fig. 5, two swollen sample sheets were overlapped at one end and sandwiched between two glass sheets, and the glass sheets were pressed and held for a certain period of time to completely fuse the sample sheets together. And (4) removing the glass sheet, taking out the sample sheet, naturally placing the sample sheet, and successfully welding the two sample sheets after the solvent in the catalyst solution is naturally volatilized.

(6) Dissolution of waste liquid crystal elastomer splines

Rectangular sample strips with the length multiplied by the width of 1.5cm multiplied by 5mm are cut from the prepared multi-domain epoxy liquid crystal elastomer sample pieces.

1,5, 7-triazabicyclo [4.4.0] dec-5-ene was dissolved in dichloromethane to prepare a catalyst solution, wherein the concentration of 1,5, 7-triazabicyclo [4.4.0] dec-5-ene in the solution was 0.25 g/ml.

The epoxy liquid crystal elastomer waste sample strips with the length multiplied by the width of 1.5cm multiplied by 5mm are completely soaked in the catalyst solution under the room temperature environment, and after a period of time, the waste sample strips are found to be completely dissolved.

Example 2

(1) Preparation of multidomain liquid crystal elastomer sample

A mixture of 0.340g (1mmol) of 4, 4' -dihydroxy-. alpha. -methyl-1, 2-stilbene diglycidyl ether (DGE-DHMS) and 0.202g (1mmol) of sebacic acid was placed in a petri dish covered with a Polytetrafluoroethylene (PTFE) membrane, melted in a heating mantle at 180 ℃ and mixed well with gentle stirring. And taking out the reaction system when the viscosity of the reaction system is increased but the reaction system is not reacted until the solid can still be drawn, and slightly cooling the reaction system to obtain the prepolymer. And (3) putting the prepolymer into two layers of Polytetrafluoroethylene (PTFE) films, using tinfoil as a gasket to control the thickness of the prepolymer film, and then carrying out hot pressing and curing on the prepolymer in a tablet press for 6 hours under the conditions of 6MPa and 180 ℃ to obtain a liquid crystal elastomer sample with the target thickness.

The catalyst solution is prepared by dissolving zinc acetate in dichloromethane, wherein the concentration of the zinc acetate in the solution is 0.005 g/ml.

Cutting the prepared multi-domain epoxy liquid crystal elastomer sample into a rectangular sample strip, placing the rectangular sample strip in the catalyst solution at room temperature to enable the rectangular sample strip to be in contact with the catalyst in a solvent swelling state, and taking out the rectangular sample strip by using tweezers when the rectangular sample strip is swelled from white to be completely transparent. And (3) when the solvent in the catalyst solution is evaporated to the point that the sample strip is recovered, stretching the rectangular sample strip to 2 times of the original length, fixing the two ends of the sample strip, evaporating the solvent at the temperature of over 60 ℃, so that the dynamic ester exchange covalent bonds in the rectangular sample strip are subjected to exchange reaction to form a new cross-linked network structure, and finally fixing the orientation.

The oriented rectangular sample strip is heated on a hot table, and referring to fig. 2, the rectangular sample strip has reversible expansion at the liquid crystal phase transition temperature (Ti) of the epoxy liquid crystal elastomer material. When the heating temperature is lower than the liquid crystal phase transition temperature (Ti) of the epoxy liquid crystal elastomer material, the shape of the rectangular sample strip is kept unchanged; when the heating temperature is higher than or equal to the liquid crystal phase transition temperature (Ti) of the epoxy liquid crystal elastomer material, the rectangular sample strip can shrink.

(3) Patterning process for multi-domain liquid crystal elastomer sample

Cutting the prepared multi-domain epoxy liquid crystal elastomer sample into a rectangular sample strip, fixing two ends of the rectangular sample strip, then placing the rectangular sample strip on a hot table for heating until the temperature is higher than the glass transition temperature of the epoxy liquid crystal elastomer material, and stretching the rectangular sample strip in a single direction along the length direction until the elongation is about 80%.

In a room temperature environment, referring to fig. 3, a pentagram is drawn on a pre-stretched rectangular sample strip, and then the pentagram part is swelled with a catalyst solution, so that the pre-stretched rectangular sample strip is contacted with the catalyst in a swelled state, so that the dynamic ester exchange covalent bond in the rectangular sample strip is subjected to an exchange reaction to form a new cross-linked network structure and fix the orientation. And after the solvent in the catalyst solution is naturally evaporated to dryness, obtaining a sample with only the pentagram area partially oriented on the rectangular sample strip.

(4) Repair of multidomain liquid crystal elastomer sample

And (3) under the room temperature environment, then placing the multi-domain epoxy liquid crystal elastomer sample into a catalyst solution, taking out the multi-domain epoxy liquid crystal elastomer sample after a period of time, and observing to ensure that scratches on the surface of the multi-domain epoxy liquid crystal elastomer sample disappear.

(5) Hole repair for multi-domain liquid crystal elastomer sample

Under the room temperature environment, a small hole is cut in the middle of one multi-domain epoxy liquid crystal elastomer sample, and then a square sample with the area larger than the diameter of the small hole is cut from the other multi-domain epoxy liquid crystal elastomer sample. And (3) placing the two sample wafers in a catalyst solution, and taking out the sample wafers by using tweezers when the sample wafers are swelled from white to be completely transparent. Referring to fig. 6, a square coupon is placed over the perforated coupon and sandwiched between two glass sheets, and the glass sheets are pressed and held for a period of time to completely fuse the two coupons together. And removing the glass sheet, taking out the sample sheet, naturally placing the sample sheet, and successfully repairing the hole in the sample sheet after the solvent in the catalyst solution is naturally volatilized.

(6) Dissolution of waste liquid crystal elastomer splines

The obtained multi-domain epoxy liquid crystal elastomer sample is cut into rectangular sample strips with the length multiplied by the width of 1.5cm multiplied by 5 mm.

The catalyst solution was prepared by dissolving zinc acetate in dichloromethane, wherein the concentration of zinc acetate in the solution was 0.1 g/ml.

A waste sample of epoxy liquid crystal elastomer having a length of 1.5cm by 5mm was completely immersed in the above catalyst solution at room temperature, and after a lapse of time, it was found that the waste sample had completely dissolved.

While the invention has been described with reference to specific embodiments, the scope of the invention is not limited thereto, and those skilled in the art can easily conceive various equivalent modifications or substitutions within the technical scope of the invention. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A method for orienting a polymeric material comprising dynamic covalent bonds and having a cross-linked network structure, the method comprising the steps of:

s10, enabling at least part of molecular chains in the cross-linked network structure of the polymer material to be oriented along a preset direction;

s20, contacting the polymer material with a catalyst capable of catalyzing the exchange reaction of dynamic covalent bonds in a swelling state in a solvent, so as to exchange the dynamic covalent bonds, thereby forming a new cross-linked network structure, wherein the catalyst capable of catalyzing the exchange reaction of dynamic covalent bonds is dissolved in the solvent.

2. The method of claim 1, wherein the dynamic covalent bond comprises a dynamic interesterified covalent bond.

3. The method of claim 1,

the polymer material is a liquid crystal elastomer material or a non-liquid crystal glass polymer material,

4. The method according to any one of claims 1 to 3, wherein in step S10, the method for orienting at least a part of molecular chains in the cross-linked network structure of the polymer material along a predetermined direction comprises: performing pre-stretching treatment on the liquid crystal elastomer material; or performing pre-shaping treatment on the non-liquid crystal system glass polymer material.

5. The method of claim 1,

the solvent comprises one or more of dichloromethane, trichloromethane and tetrahydrofuran;

the catalyst is a basic catalyst, and the basic catalyst preferably comprises one or more of 1,5, 7-triazabicyclo [4.4.0] dec-5-ene, zinc acetate and palladium triphenylphosphine.

6. The method of claim 1, wherein the catalyst capable of catalyzing the dynamic covalent bond exchange reaction is dissolved in the solvent to form a catalyst solution, and the concentration of the catalyst solution is 0.0005g/ml to 0.1 g/ml.

7. The method according to claim 1, wherein the swelling temperature is 15 to 100 ℃ in step S20.

8. A method for patterning a polymeric material comprising dynamic covalent bonds and having a cross-linked network structure, the method comprising the steps of:

s100, enabling at least part of molecular chains in a cross-linked network structure of the polymer material to be oriented along a preset direction;

s200, contacting the polymer material with a catalyst capable of catalyzing dynamic covalent bond exchange reaction in a swelling state in a solvent so as to enable the dynamic covalent bond to perform exchange reaction, thereby forming a new cross-linked network structure and further enabling the polymer material to have different patterns, wherein the catalyst capable of catalyzing dynamic covalent bond exchange reaction is dissolved in the solvent.

9. A method for repairing a polymeric material comprising dynamic covalent bonds and having a cross-linked network structure, the method comprising the steps of:

and contacting the damaged part to be repaired of the polymer material with a catalyst capable of catalyzing dynamic covalent bond exchange reaction in a solvent in a swelling state so as to enable the dynamic covalent bond to perform exchange reaction, thereby forming a new cross-linked network structure on the damaged part to be repaired to realize repair, wherein the catalyst capable of catalyzing dynamic covalent bond exchange reaction is dissolved in the solvent.

10. A method for scavenging a polymeric material comprising dynamic covalent bonds and having a cross-linked network structure, comprising the steps of:

and contacting the part to be eliminated of the polymer material with a catalyst capable of catalyzing dynamic covalent bond exchange reaction in a swelling state in a solvent so as to enable the dynamic covalent bond exchange reaction to occur and further eliminate the part to be eliminated, wherein the catalyst capable of catalyzing the dynamic covalent bond exchange reaction is dissolved in the solvent.

11. A method for welding polymeric materials comprising dynamic covalent bonds and having a cross-linked network structure, the method comprising the steps of: