Solvent response shape memory polymer and preparation method thereof

Abstract

The invention discloses a solvent response shape memory polymer and a preparation method thereof, relates to the technical field of shape memory polymers, and discloses the solvent response shape memory polymer which comprises urethane acrylate, polystyrene-block isoprene-polystyrene and a photoinitiator. The solvent response shape memory polymer provided by the invention realizes a solvent response shape memory effect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of shape memory polymers, in particular to a solvent-responsive shape memory polymer and a preparation method thereof. BACKGROUND

[0002] Shape Memory Polymers (SMPs) are a class of functional polymer materials with intelligent response characteristics, which can recover from a temporary shape to an original shape under external stimuli. In recent years, such materials have shown wide application prospects in the fields of biomedical, flexible electronics, intelligent textiles and aerospace. At present, most shape memory polymers mainly rely on temperature as the external stimulus source to trigger shape recovery, that is, by heating above the glass transition temperature (T g ) or melting point (T m ) of the polymer, the movement of the polymer chain segment is activated, thereby realizing shape memory effect. However, the response mechanism of conventional temperature-sensitive shape memory polymers is single, and they are usually sensitive only to temperature changes, which is difficult to adapt to diversified application scenarios. SUMMARY

[0003] The main purpose of the present application is to provide a solvent-responsive shape memory polymer and a preparation method thereof, which realizes solvent-responsive shape memory effect.

[0004] To achieve the above purpose, the present application provides a solvent-responsive shape memory polymer, which comprises: polyurethane acrylate, polystyrene-block-isoprene-polystyrene and a photoinitiator.

[0005] In an embodiment, the polyurethane acrylate comprises aliphatic polyurethane acrylate and / or aromatic polyurethane acrylate.

[0006] In an embodiment, the photoinitiator comprises at least one of a free radical type photoinitiator, a cationic type photoinitiator and a bifunctional photoinitiator.

[0007] In an embodiment, the mass ratio between the polyurethane acrylate and the polystyrene-block-isoprene-polystyrene in the solvent-responsive shape memory polymer is (1:4) to (2:1).

[0008] In an embodiment, the photoinitiator accounts for 0.5 to 10% of the total mass of the solvent-responsive shape memory polymer.

[0009] In an embodiment, the response solvent of the solvent-responsive shape memory polymer comprises at least one of non-polar alkane solvents, weakly polar alkane solvents and polar organic solvents.

[0010] In an embodiment, the solvent-responsive shape memory polymer has a glass transition temperature of 60-100°C.

[0011] In addition, to achieve the above object, the application further provides a preparation method of the solvent-responsive shape memory polymer, which is applied to the preparation of the solvent-responsive shape memory polymer as described above, and comprises the following steps:

[0012] mixing polyurethane acrylate, polystyrene-block-isoprene-polystyrene and an organic solvent to obtain a precursor solution;

[0013] adding a photoinitiator to the precursor solution and stirring uniformly to obtain a mixed solution;

[0014] photocuring the mixed solution to obtain the solvent-responsive shape memory polymer.

[0015] In an embodiment, the stirring time of the mixed precursor solution and the photoinitiator is 8-24h.

[0016] In an embodiment, the wavelength of the ultraviolet light for photocuring is 100-400nm.

[0017] The one or more technical solutions provided in the application have at least the following technical effects: a solvent-responsive shape memory polymer is provided, which comprises polyurethane acrylate, polystyrene-block-isoprene-polystyrene and a photoinitiator. In the solvent-responsive shape memory polymer (hereinafter referred to as polymer) of the embodiment of the application, the double bond in the polyurethane acrylate molecule can undergo an addition reaction under the action of the photoinitiator to cross-link to form a rigid three-dimensional network structure, and the polystyrene-block-isoprene-polystyrene and the polyurethane acrylate are also tightly connected by the cross-linking points generated by the addition reaction to form a cross-linked network. Furthermore, in the cross-linked network formed, the network structure formed by the polyurethane acrylate has poor compatibility with part of the solvent (for example, non-polar alkane solvents, weakly polar alkane solvents, polar organic solvents and the like), and is not easily affected by the solvent, so it can act as a stationary phase in the polymer, giving the polymer excellent mechanical strength and shape memory fixing ability. The polystyrene-block-isoprene-polystyrene in the polymer has a flexible segment, so the network structure formed by it can form a deformable soft phase, giving the polymer good ductility and shape reversibility; at the same time, when the segment of the polystyrene-block-isoprene-polystyrene contacts a specific solvent (for example, non-polar alkane solvents, weakly polar alkane solvents, polar organic solvents and the like), the solvent molecules can reduce the internal energy of the polymer system by interacting with the segment, significantly increase the activity of the segment, promote the disentanglement and rearrangement of the segment, and exhibit a certain solvent-induced plasticity effect. This plasticity effect helps to relieve local stress concentration and reduce the energy barrier required for shape recovery, thereby synergistically promoting the release of elastic energy stored in the polymer network, completing the solvent-induced shape recovery process, and achieving excellent solvent-responsive shape memory behavior. The solvent-responsive shape memory polymer provided in the embodiment of the application can respond to various solvents such as non-polar alkane solvents, weakly polar alkane solvents, polar organic solvents and the like, effectively expanding the types of solvents that the solvent-responsive shape memory polymer can respond to. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 Flowchart of the solvent-responsive shape memory polymer preparation method involved in the embodiment of the application;

[0019] Figure 2 Shape memory effect test diagram of Example 1 of the application at 90℃;

[0020] Figure 3 Shape memory effect test diagram of Example 1 of the application in petroleum;

[0021] Figure 4 Shape memory effect test diagram of Example 1 of the application in petroleum ether;

[0022] Figure 5Test chart for shape memory effect of Example 1 of the present application in DMF.

[0023] The object, functional features and advantages of the present application will be further described with reference to the embodiments, with reference to the accompanying drawings. DETAILED DESCRIPTION

[0024] In order to make the object, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be described clearly and completely below. If the specific conditions are not mentioned in the embodiments, the conventional conditions or the conditions suggested by the manufacturers are adopted. If the reagents or instruments are not mentioned by the manufacturers, they are all the conventional products which can be purchased in the market.

[0025] Hereinafter, the embodiments of the solvent-responsive shape memory polymer and the preparation method thereof disclosed in the present application will be specifically described with reference to the accompanying drawings as appropriate. However, there will be cases where unnecessary detailed description is omitted. For example, there will be cases where detailed description of matters which are already well known, and repeated description of substantially the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the accompanying drawings and the following description are provided in order for those skilled in the art to fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0026] The "ranges" disclosed in the present application are defined in the form of lower and upper limits, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The ranges defined in this way can include or exclude the end values, and can be arbitrarily combined, i.e., any lower limit can be combined with any upper limit to form a range. For example, if the ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that the ranges of 60-110 and 80-120 are also contemplated. In addition, if the minimum range values of 1 and 2 are listed, and if the maximum range values of 3, 4 and 5 are listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "a-b" represents a shorthand notation for any real combination of integers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed herein, and "0-5" is just a shorthand notation for these numerical combinations. In addition, when it is stated that a parameter is an integer ≥ 2, it is equivalent to disclose that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0027] If not specifically stated, all the embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions.

[0028] If not particularly specified, all the technical features and optional technical features of the present application can be combined with each other to form new technical solutions.

[0029] If not particularly specified, all the steps of the present application can be performed in sequence or randomly, and preferably in sequence. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) performed in sequence, or steps (b) and (a) performed in sequence. For example, it is mentioned that the method can further comprise step (c), which means that step (c) can be added to the method in any order. For example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0030] If not particularly specified, the "comprise" and "include" mentioned in the present application are open-ended, and can also be closed. For example, "comprise" and "include" can mean that other components not listed can also be included or contained, or only the listed components can be included or contained.

[0031] If not particularly specified, in the present application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfy the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or A and B are both true (or exist).

[0032] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the technical solutions of the present application will be further described below in combination with the drawings and examples. However, the present application is not limited to the listed examples, and any known changes within the scope of the claimed rights of the present application should also be included.

[0033] The "one embodiment" or "embodiment" referred to herein means that the specific features, structures or characteristics can be included in at least one implementation of the present application. The "in one embodiment" appearing in different places in the specification does not mean the same embodiment, nor is it an embodiment that is mutually exclusive with other embodiments.

[0034] In order to better understand the technical solutions of the present application, the technical solutions of the present application will be described in detail below in combination with the drawings and specific embodiments.

[0035] In conventional technology, solvent-responsive shape memory polymers have the problem of limited response to solvent types. Generally, they only show good response to a single type of solvent, which is difficult to meet the needs of diversified solvent stimulation in complex environments.

[0036] The application provides a solution, specifically, a solvent-responsive shape memory polymer, comprising: polyurethane acrylate, polystyrene-block-isoprene-polystyrene and a photoinitiator. In the solvent-responsive shape memory polymer (hereinafter referred to as polymer) of the embodiment of the application, the double bond in the polyurethane acrylate molecule can undergo addition reaction under the action of the photoinitiator to crosslink to form a rigid three-dimensional network structure, and the polystyrene-block-isoprene-polystyrene and the polyurethane acrylate are also closely connected by the crosslinking points generated by the addition reaction to form a crosslinked network. Furthermore, in the crosslinked network formed, the network structure formed by the polyurethane acrylate has poor compatibility with part of the solvent (for example, non-polar alkane solvents, weakly polar alkane solvents, polar organic solvents and the like) and is not easily affected by the solvent, and therefore can serve as a stationary phase in the polymer to endow the polymer with excellent mechanical strength and shape memory fixing ability. The polystyrene-block-isoprene-polystyrene in the polymer has a flexible segment, and therefore the network structure formed by the polystyrene-block-isoprene-polystyrene can form a deformable soft phase to endow the polymer with good ductility and shape reversibility; at the same time, when the segment of the polystyrene-block-isoprene-polystyrene contacts a specific solvent (for example, non-polar alkane solvents, weakly polar alkane solvents, polar organic solvents and the like), the solvent molecules can reduce the internal energy of the polymer system by interacting with the segment to significantly improve the activity of the segment, promote the disentanglement and rearrangement of the segment, and exhibit a certain solvent-induced plasticity effect. The plasticity effect helps to relieve local stress concentration, reduce the energy barrier required for shape recovery, and therefore cooperatively promotes the release of the elastic energy stored in the polymer network to complete the solvent-induced shape recovery process and realize excellent solvent-responsive shape memory behavior. The solvent-responsive shape memory polymer provided in the embodiment of the application can respond to various solvents such as non-polar alkane solvents, weakly polar alkane solvents, polar organic solvents and the like, and effectively expands the types of solvents that can be responded to by the solvent-responsive shape memory polymer.

[0037] The first aspect of the embodiment of the application provides a solvent-responsive shape memory polymer, which comprises: polyurethane acrylate, polystyrene-block-isoprene-polystyrene and a photoinitiator.

[0038] Optionally, the shape memory principle of the shape memory polymer is that when the temperature is above the transition temperature, the shape memory polymer can be deformed under the action of an external force, when the temperature is lowered to below the transition temperature, the shape memory polymer can fix the shape, and when the external force is removed and the temperature is raised again to above the transition temperature, the polymer will return to the original shape. On this basis, after the solvent-responsive shape memory polymer contacts a specific solvent, the interaction between the molecular chains is weakened, the transition temperature of the material is lowered to below room temperature, which is equivalent to that the room temperature is already higher than the transition temperature of the material, and therefore shape recovery can occur.

[0039] Optionally, the polyurethane acrylate is a polymer combining the advantages of polyurethane and acrylate, which is usually prepared by reacting polyurethane containing hydroxyl with acrylic acid or methacrylic acid, and has good mechanical properties, wear resistance, chemical resistance and excellent adhesion. In the embodiments of the present application, the cross-linking reaction of the acrylic double bond in the polyurethane acrylate is initiated by the photoinitiator to form a dense and rigid three-dimensional network structure, which reduces the interaction between the material and the solvent, effectively acts as a stationary phase in the shape memory polymer, and thus endows the material with excellent mechanical strength and shape memory fixing performance.

[0040] Optionally, the polystyrene-block-isoprene-polystyrene (SIS, Styrene-Isoprene-Styrene block copolymer) is a thermoplastic elastomer composed of hard polystyrene blocks and soft polyisoprene blocks. Since SIS has flexible segments, it can form a deformable soft phase, so adding it to the solvent-responsive shape memory polymer can endow the polymer with good ductility and shape reversibility; at the same time, the segments of polystyrene-block-isoprene-polystyrene can quickly penetrate and adsorb when contacting specific solvents (for example, non-polar alkane solvents, weakly polar alkane solvents, polar organic solvents, etc.), reducing the interaction force and internal energy between the polymer segments, increasing the activity of the segments, thus triggering the release of elastic energy stored in the polymer network, completing the solvent-induced shape recovery process, and achieving the solvent-responsive shape memory effect.

[0041] Optionally, the photoinitiator is a compound that can produce active species (such as free radicals or cations) after absorbing light energy, which can further initiate chemical reactions between monomers, oligomers or polymers, such as polymerization or cross-linking reaction. In the embodiments of the present application, by adding the photoinitiator, the solvent-responsive shape memory polymer can, under the action of light energy, initiate the cross-linking reaction of the acrylic double bond in the polyurethane acrylate by the photoinitiator to form a rigid three-dimensional network structure. At the same time, the photoinitiator promotes the polymerization of the polyurethane acrylate and the polystyrene-block-isoprene-polystyrene, which combines the rigid network and the flexible segment, and constructs a double-network structure with excellent mechanical properties and controllable shape memory effect.

[0042] Optionally, the solvent-responsive shape memory polymer is formed by light curing.

[0043] In a feasible implementation, the response solvent of the solvent-responsive shape memory polymer includes at least one of a non-polar alkane solvent, a weakly polar alkane solvent and a polar organic solvent.

[0044] Optionally, the non-polar alkane solvent includes at least one of petroleum, petroleum ether, cyclohexane and n-pentane.

[0045] Optionally, the weakly polar alkane solvent includes toluene and / or dichloromethane. SIS is composed of non-polar polystyrene blocks and weakly polar polyisoprene blocks, and thus has good compatibility with non-polar alkane solvents and weakly polar alkane solvents (such as toluene and dichloromethane). Therefore, the solvent-responsive shape memory polymer prepared based on SIS in the embodiments of the present application can also respond to non-polar alkane solvents and weakly polar alkane solvents.

[0046] Optionally, the polar organic solvent includes at least one of acetone, DMF and diethyl ether. The polar solvent has limited solubility for SIS, but the solvent can still cause SIS to swell due to the similarity of part of the molecular chain segments. Therefore, the solvent-responsive shape memory polymer in the embodiments of the present application can respond to the polar solvent.

[0047] In an implementation, the polyurethane acrylate includes aliphatic polyurethane acrylate and / or aromatic polyurethane acrylate.

[0048] Optionally, the polyurethane acrylate can also be modified polyurethane acrylate, for example, modified polyurethane acrylate with specific functional groups.

[0049] In an implementation, the mass ratio between the polyurethane acrylate and the polystyrene-block-isoprene-polystyrene in the solvent-responsive shape memory polymer is (1:4) to (2:1), i.e., the mass of the polyurethane acrylate / the mass of the polystyrene-block-isoprene-polystyrene = 0.25 to 2.

[0050] Optionally, the mass of the polyurethane acrylate / the mass of the polystyrene-block-isoprene-polystyrene in the solvent-responsive shape memory polymer can be 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, etc.

[0051] In the solvent-responsive shape memory polymer of the embodiments of the present application, the polyurethane acrylate provides a rigid network to maintain the basic structure and shape recovery ability of the polymer, and the polystyrene-block-isoprene-polystyrene provides a flexible network to endow the material with flexibility and solvent-responsive characteristics. If the amount of polyurethane acrylate is too small, the overall rigidity and shape stability of the polymer will be significantly reduced, resulting in the material being unable to effectively recover to the original shape after the external stress is removed, and reducing the functionality thereof as a shape memory material. In addition, due to the lack of sufficient physical or chemical crosslinking points, the polymer can become too soft and even exhibit viscous flow, which greatly limits its range of use in practical applications. Conversely, if the amount of polyurethane acrylate is too large, the polymer will be too hard and lose the necessary elasticity and flexibility, making it difficult for the material to deform through external stimulation (such as solvent action), and it can also affect the processability of the polymer. On the other hand, if the amount of polystyrene-block-isoprene-polystyrene is insufficient, the polymer will lack sufficient flexibility and solvent-responsive ability, resulting in its being unable to fully expand or deform when it comes into contact with a specific solvent, thereby affecting the reversible deformation ability and reusability of the material. At the same time, a lower content of the flexible component can also cause stress concentration within the polymer, increasing the risk of material fracture. Conversely, if the amount of polystyrene-block-isoprene-polystyrene is too large, although it can enhance the flexibility and solvent responsiveness of the material, it will also weaken the shape memory effect, because a too high proportion of flexible component will reduce the rigid nodes in the polymer system, making it difficult for the material to maintain the preset temporary shape after losing external support, and it can also result in poor mechanical strength and durability. Therefore, in the embodiments of the present application, the mass ratio between the polyurethane acrylate and the polystyrene-block-isoprene-polystyrene in the solvent-responsive shape memory polymer is determined to be (1:4) to (2:1).

[0052] In an implementation, the photoinitiator includes at least one of a free radical photoinitiator, a cationic photoinitiator, and a bifunctional photoinitiator.

[0053] The free radical photoinitiator is a photoinitiator capable of generating free radical active species upon irradiation of ultraviolet light or visible light, and the generated free radical active species can initiate chain radical polymerization of monomers containing unsaturated double bonds (such as acrylates). Such photoinitiators have the characteristics of fast reaction speed and high curing efficiency.

[0054] Optionally, the free radical photoinitiator includes at least one of 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (TPO), 1-hydroxycyclohexyl phenyl ketone, 2,2-dimethoxy-1,2-diphenyl ethan-1-one, and 2-hydroxy-2-methyl-1-phenyl-1-propanone.

[0055] Cationic photoinitiators are photoinitiators that generate active cations (such as super acids) upon photoexcitation, and then initiate cationic polymerization of monomers such as epoxy resins and vinyl ethers. Compared with radical reactions, cationic polymerization has the advantages of being unaffected by oxygen, low shrinkage, stable performance after curing, and is particularly suitable for thick coating or deep curing applications.

[0056] Optionally, the cationic photoinitiator includes at least one of aromatic diazonium salts, sulfonium salts, and iron arene complexes.

[0057] Bifunctional photoinitiators are photoinitiators that contain two different initiation functions in the same molecular structure, such as both radical initiation and cationic initiation capabilities, or two initiation sites of the same type but can respond to light energy respectively in one molecule. This design can achieve synergistic effect, improve the efficiency of photoinitiation, broaden the absorption spectrum range, or trigger multiple polymerization mechanisms in the same material, thereby obtaining more excellent comprehensive performance.

[0058] Optionally, the bifunctional photoinitiator includes oxime ester photoinitiators and / or sulfur-containing xanthone derivatives.

[0059] In an embodiment, the photoinitiator accounts for 0.5-10% of the total mass of the solvent-responsive shape memory polymer, for example, the photoinitiator accounts for 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10% of the total mass of the solvent-responsive shape memory polymer, etc. If the amount of photoinitiator is too small, it may lead to incomplete polymerization or significantly reduced reaction rate, which means that under light conditions, the number of free radicals or cations generated is not enough to effectively start the full crosslinking process between the components and between them, resulting in a polymer network structure that is not dense enough, which may lead to insufficient mechanical strength of the material, poor shape memory effect, and decreased sensitivity to solvent response. On the contrary, if the amount of photoinitiator is too large, it may lead to excessive local reaction, forming a local overheating phenomenon, thereby damaging the microstructure and macroscopic properties of the material. At the same time, it may lead to excessive crosslinking, and the polymer becomes too hard, losing the necessary flexibility and elasticity, thereby affecting its key properties as a shape memory polymer, such as deformation ability and recovery force. Therefore, the embodiments of the present application determine that the photoinitiator accounts for 0.5-10% of the total mass of the solvent-responsive shape memory polymer.

[0060] In an embodiment, the glass transition temperature T g of the solvent-responsive shape memory polymer is 60-100°C. Since the T gat 60-100℃, so that the segment movement of the polymer is limited at room temperature, and the material is in a glassy or hard state, at which the polymer does not have sufficient segment activity to realize the shape memory and recovery functions; under the action of the solvent, solvent molecules can be inserted between the polymer chains, increase the distance between the chains and reduce the interaction between the chains, thus playing a plasticizing role, which can effectively reduce the T g so that the polymer originally in a glassy state at room temperature is transformed into a rubbery or high-elastic state, and further realizes the shape memory and recovery functions.

[0061] Optionally, the solvent-responsive shape memory polymer has excellent mechanical properties and shape memory effect in response to the solvent, and is thus suitable for use in multiple fields such as biomedical devices, tissue engineering, soft body driving, etc.

[0062] Optionally, the solvent-responsive shape memory polymer can be used as an adsorption material, and the selected swelling adsorption response solvent (for example, petroleum) can also be applied to sensors, for example, in combination with conductive fillers, and then the circuit conduction is adjusted by the solvent to trigger the deformation, so as to serve as a humidity or chemical sensor.

[0063] In the embodiment, a solvent-responsive shape memory polymer is provided, comprising: polyurethane acrylate, polystyrene-block-isoprene-polystyrene and a photoinitiator. In the solvent-responsive shape memory polymer (hereinafter referred to as polymer) of the embodiment, the double bond in the polyurethane acrylate molecule can undergo addition reaction under the action of the photoinitiator to crosslink to form a rigid three-dimensional network structure, and the polystyrene-block-isoprene-polystyrene and the polyurethane acrylate are also tightly connected by the crosslinking points generated by the addition reaction to form a crosslinked network. Furthermore, in the crosslinked network formed, the network structure formed by the polyurethane acrylate has poor compatibility with part of the solvent (for example, non-polar alkane solvents, weakly polar alkane solvents, polar organic solvents, etc.) and is not easily affected by the solvent, so it can act as a stationary phase in the polymer to give the polymer excellent mechanical strength and shape memory fixing ability. The polystyrene-block-isoprene-polystyrene in the polymer has a flexible segment, so the network structure formed by it can form a deformable soft phase to give the polymer good ductility and shape reversibility; at the same time, when the segment of the polystyrene-block-isoprene-polystyrene contacts a specific solvent (for example, non-polar alkane solvents, weakly polar alkane solvents, polar organic solvents, etc.), the solvent molecules can reduce the internal energy of the polymer system by interacting with the segment, significantly increase the activity of the segment, promote the disentanglement and rearrangement of the segment, and exhibit a certain solvent-induced plasticity effect. This plasticity effect helps to relieve local stress concentration and reduce the energy barrier required for shape recovery, thereby synergistically promoting the release of elastic energy stored in the polymer network to complete the solvent-induced shape recovery process and achieve excellent solvent-responsive shape memory behavior. The solvent-responsive shape memory polymer provided in the embodiment can respond to various solvents such as non-polar alkane solvents, weakly polar alkane solvents, polar organic solvents, etc., effectively expanding the types of solvents that the solvent-responsive shape memory polymer can respond to.

[0064] The second aspect of the embodiment provides a solvent-responsive shape memory polymer preparation method, which refers to Figure 1 The solvent-responsive shape memory polymer preparation method comprises the following steps:

[0065] In step S10, the polyurethane acrylate, the polystyrene-block-isoprene-polystyrene and the organic solvent are mixed to obtain a precursor solution.

[0066] Optionally, the organic solvent is a low-boiling-point solvent that can dissolve the polyurethane acrylate and the polystyrene-block-isoprene-polystyrene, so as to be quickly volatilized in the subsequent photocuring process and avoid being left in the polymer.

[0067] Optionally, the organic solvent comprises dichloromethane.

[0068] Optionally, the polyurethane acrylate includes: aliphatic polyurethane acrylate and / or aromatic polyurethane acrylate.

[0069] Optionally, the mass ratio between polyurethane acrylate and polystyrene-block isoprene-polystyrene is (1:4) to (2:1).

[0070] Step S20, adding a photoinitiator to the precursor solution and stirring evenly to obtain a mixed solution;

[0071] In one feasible embodiment, a photoinitiator is added to the precursor solution and stirred, wherein the stirring time is 8 to 24 hours, for example, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours, 21 hours, 22 hours, 23 hours, 24 hours, etc., so that the precursor solution and the photoinitiator are evenly mixed to obtain a mixed solution.

[0072] Optionally, the photoinitiator includes at least one of a free radical photoinitiator, a cationic photoinitiator and a bifunctional photoinitiator.

[0073] Optionally, the photoinitiator accounts for 0.5-10% of the total mass of the solvent-responsive shape memory polymer.

[0074] Step S30 , photocuring the mixed solution to obtain a solvent-responsive shape memory polymer.

[0075] In a feasible embodiment, the mixed solution is poured into a preset mold and subjected to UV curing, wherein the wavelength of the UV light for photocuring is 100 to 400 nm and the curing time is 0.2 to 2 hours to obtain a solvent-responsive shape memory polymer.

[0076] Optionally, the solvent-responsive shape memory polymer has a thickness of 0.01 to 5 mm.

[0077] In the present embodiment, the solvent-responsive shape memory polymer is prepared by a light-curing method, which is simple in process and can be customized according to actual needs, and is easy to mass-produce. Further, the cross-linked polyurethane acrylate in the solvent-responsive shape memory polymer (hereinafter referred to as the polymer) has poor compatibility with some solvents (for example, non-polar alkane solvents, weakly polar alkane solvents, polar organic solvents, etc.), and is not easily affected by the solvents. Therefore, the cross-linking reaction of the acrylic double bond in the polyurethane acrylate can be initiated by a photoinitiator to form a rigid three-dimensional network structure to serve as a fixed phase in the polymer, thereby giving the polymer excellent mechanical strength and shape memory fixing ability. The polystyrene-block-isoprene-polystyrene in the polymer has a flexible segment, which can form a deformable soft phase to give the polymer good ductility and shape reversibility. At the same time, the segment of polystyrene-block-isoprene-polystyrene can quickly penetrate and adsorb when contacting a specific solvent (for example, non-polar alkane solvents, weakly polar alkane solvents, polar organic solvents, etc.), thereby reducing the interaction force and internal energy between the polymer segments and increasing the activity of the segments, so as to trigger the release of the elastic energy stored in the polymer network and complete the solvent-induced shape recovery process to achieve the solvent-responsive shape memory effect. The solvent-responsive shape memory polymer provided in the present embodiment can respond to various solvents such as non-polar alkane solvents, weakly polar alkane solvents, polar organic solvents, etc., thereby effectively expanding the types of responsive solvents for the solvent-responsive shape memory polymer.

[0078] In order to enable the above-mentioned details and operations of the embodiments of the present application to be clearly understood by those skilled in the art, and the significant performance of the embodiments of the present application to be embodied, the above-mentioned technical solutions are illustrated by multiple embodiments as follows.

[0079] Embodiment 1

[0080] (1) 1 g of aliphatic polyurethane acrylate and 2 g of polystyrene-block-isoprene-polystyrene were added to 15 g of dichloromethane for mixing to obtain a precursor solution;

[0081] (2) 0.06 g of a photoinitiator TPO was added to the precursor solution, and the mixture was stirred at 200 rpm for 12 h under light shielding to obtain a mixed solution;

[0082] (3) The mixed solution was poured into a pre-set mold, and cured under ultraviolet light at 395 nm for 30 min to obtain a solvent-responsive shape memory polymer.

[0083] The thermal shape memory effect of the polymer in Embodiment 1 was tested by using a dynamic mechanical analyzer, and the test results are referred to Figure 2 , and the test process includes:

[0084] (1) The sample (polymer) is heated to 90℃ for 10 min, and stress is applied to maintain an initial strain of 30%;

[0085] (2) The temperature is cooled to 25℃, the stress is released, and the deformation strain of the sample is recorded;

[0086] (3) The sample is reheated to 90℃, at which time the sample gradually recovers from the temporary shape to the initial shape.

[0087] According to Figure 2 The results show that the application of external force under conditions higher than the glass transition temperature (T g ) can cause plastic deformation of the material, and then cooling to below T g under stress conditions can fix the temporary shape; after the external force is removed, the deformation of the material does not change much, maintaining a high shape fixation rate. Further, when the temperature is raised again to above T g , the material recovers to the initial shape, showing excellent shape recovery rate. The results verify the excellent shape fixation and shape recovery performance of the material, and reflect the good thermal response shape memory characteristics.

[0088] Further, the polymer in Example 1 was subjected to solvent response testing, and the results are shown in Figures 3 to 5 The testing process includes:

[0089] (1) A plurality of samples (polymers) are placed on a heating stage, wherein the initial shapes of the samples are as shown in Figure 3 (a), Figure 4 (a), and Figure 5 (a), respectively, and then heated to 90℃ to fix the shape while maintaining the external force;

[0090] (2) The temperature is cooled to 25℃, and the stress is released, wherein the temporary shapes of the samples are as shown in Figure 3 (b), Figure 4 (b), and Figure 5 (b), respectively;

[0091] (3) The samples are placed in containers containing the response solvent, respectively, and the shape of the samples is observed, wherein Figure 3 (c) shows the shape change of the sample after being placed in a container containing petroleum, and the sample gradually recovers from the temporary shape to the initial shape; Figure 4 (c) shows the shape change of the sample after being placed in a container containing petroleum ether, and the sample gradually recovers from the temporary shape to the initial shape; Figure 5 (c) shows the shape change of the sample after being placed in a container containing DMF, and the sample gradually recovers from the temporary shape to the initial shape.

[0092] It can be known by the above tests that the solvent-responsive shape memory polymer provided by the embodiments of the present application has a higher shape recovery rate in petroleum, petroleum ether and DMF, and has excellent solvent-responsive shape memory effect on various solvents.

[0093] The above are only preferred embodiments of the present application, and do not limit the patent scope of the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the patent protection scope of the present application.

Claims

1. A solvent-responsive shape memory polymer, characterized in that The solvent-responsive shape memory polymer comprises polyurethane acrylate, polystyrene-block isoprene-polystyrene and a photoinitiator.

2. The solvent-responsive shape memory polymer according to claim 1, wherein The polyurethane acrylate includes: aliphatic polyurethane acrylate and / or aromatic polyurethane acrylate.

3. The solvent-responsive shape memory polymer according to claim 1, wherein The photoinitiator includes at least one of a free radical photoinitiator, a cationic photoinitiator and a bifunctional photoinitiator.

4. The solvent-responsive shape memory polymer according to claim 1, wherein The mass ratio of polyurethane acrylate to polystyrene-block isoprene-polystyrene in the solvent-responsive shape memory polymer is (1:4) to (2:1).

5. The solvent-responsive shape memory polymer according to claim 1, wherein The photoinitiator accounts for 0.5-10% of the total mass of the solvent-responsive shape memory polymer.

6. The solvent-responsive shape memory polymer according to claim 1, wherein The responsive solvent of the solvent-responsive shape memory polymer includes at least one of a non-polar alkane solvent, a weakly polar alkane solvent and a polar organic solvent.

7. The solvent-responsive shape memory polymer according to claim 1, wherein The glass transition temperature of the solvent-responsive shape memory polymer is 60-100°C.

8. A method for preparing a solvent-responsive shape memory polymer, characterized in that: For preparing the solvent-responsive shape memory polymer according to any one of claims 1 to 8, the method comprises the following steps: mixing polyurethane acrylate, polystyrene-block isoprene-polystyrene and an organic solvent to obtain a precursor solution; adding a photoinitiator to the precursor solution and stirring uniformly to obtain a mixed solution; The mixed solution is photocured to obtain a solvent-responsive shape memory polymer.

9. The method for preparing a solvent-responsive shape memory polymer according to claim 8, wherein: The stirring time after the precursor solution and the photoinitiator are mixed is 8 to 24 hours.

10. The method for preparing a solvent-responsive shape memory polymer according to claim 8, wherein: The wavelength of the ultraviolet light for photocuring is 100-400 nm.

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