CN104592453A - Polymer with bidirectional reversible shape memory effect and preparation method thereof - Google Patents

Abstract

The invention discloses a polymer with two-way reversible shape memory effect, comprising at least one amorphous phase and one crystalline phase, wherein the glass transition temperature of the amorphous phase is higher than the melting temperature of the crystalline phase, and the difference between the two is at least 20°C . The preparation method is to replace the high-temperature crystalline phase in the twin-crystal thermosetting reversible shape-memory polymer by using the high-temperature amorphous phase as the stress phase to prepare the single-crystal thermosetting two-way reversible shape-memory polymer. The glass transition temperature of the high-temperature amorphous phase of the polymer can be continuously regulated by different comonomers. On the premise that the glass transition temperature of the amorphous phase is higher than the crystallization phase transition temperature, the two-phase ratio and alternating phase can be realized. The control of joint density and crystallization phase transition temperature. The polymer material is light in weight, easy to process, low in cost, has excellent insulation and heat preservation effects, and has a wide range of potential application values in biomedicine, cable industry, packaging industry and other fields.

Description

Polymer with two-way reversible shape memory effect and preparation method thereof

technical field

The invention belongs to the field of new functional materials, and relates to an intelligent material and a preparation method thereof, in particular to a polymer material with two-way reversible shape memory effect and a preparation method thereof.

Background technique

The shape memory polymer in the traditional sense can form a temporary shape under the combined action of heating above its thermal transition temperature and external force, and this temporary shape can be fixed after cooling (below its thermal transition temperature). The final temporary shape can be restored to its original shape under certain external conditions (such as reheating), and its corresponding thermal transition temperature (such as glass transition temperature or crystallization temperature) is usually called the shape memory transition temperature. The shape memory polymer known for half a century can only change between a temporary shape and its permanent shape at a time, which is now called the double shape memory effect, and its essence is to use a thermal transition to memorize a temporary shape. shape. This shape memory behavior, despite its simplicity, has been successfully used commercially, for example in heat-shrinkable tubing for the cable industry and heat-shrinkable labels for the packaging industry. Other high value-added biomedical applications are also being actively explored and have gradually shown their great potential.

Recent studies have found that two completely separated thermal transition regions in the same polymer structure can realize two temporary shape-fixed triple shape memory effect systems, and a single wider region thermal transition in the same polymer can be used to fix two The temporary shape above is the adjustable multiple shape memory effect. The discovery of these new shape memory effects has greatly expanded the diversification of polymer shape memory behavior and its application prospects. Whether it is double, triple, or multiple shape memory effects, polymers can be restored from their temporary shape to their original shape by heating without external force. However, under the same condition of no external force, the polymer cannot be restored from its original shape to its temporary shape at low temperature by cooling. All of the above shape memories are irreversible, which is called one-way shape memory.

Irreversible shape memory, although it also has its practical prospects, its unidirectional deformation behavior hinders the wider application of this type of material. Terentjev's group discovered in 2001 that cross-linked liquid crystal elastomers can exhibit completely reversible thermal shrinkage and cold elongation at the liquid crystal transition temperature under the condition of hanging constant weight (that is, constant external force>0). Growth originates from the orientation of the liquid crystal in the direction of the external force, and the elimination of this orientation when heated leads to thermal shrinkage (TajbakhshAR, Terentjev EM. Eur. Phys. J. Ser. E. 2001, 6, 181.). Based on a similar mechanism, the Mather group discovered in 2008 that the cross-linked crystalline polymer network also exhibits the same behavior, but the corresponding thermal transition is a crystallization thermal transition (Chung T, Rorno-Uribe A, Mather P. Two-way reversible shape memory in a semicrystalline network. Macromolecules 2008, 41, 184.). Since then, several research groups (including the applicant) have successively reported the reversible deformation behavior of different crosslinked crystalline polymers. The advantage of this type of reversible deformation is that the deformation can be adjusted with the magnitude of a constant external force, but its disadvantages are also obvious: it cannot be realized when the external force is zero, and the condition that requires a constant external force greatly limits the possibility of its device application; Hanging constant weight, the easiest constant external force to achieve, means that deformation can only be linear elongation and contraction.

In 2010, the Hu group realized the reversible bending change of the polymer system without external force. The change of the curvature of this material is completely reversible without the action of external force (Chen S, Hu J, Zhao H. Properties and mechanism of two-way shape memory polyurethane composites. Composites Sci. Technology 2010, 70, 1437.). Although this functional improvement is very important, the disadvantages of this type of material are still significant: the macroscopic layered structure means that the material can only be applied to macroscopic devices; the internal stress of the composite material system is fixed after preparation, that is, In other words, it can only reversibly change between two constant shapes, but cannot achieve programmatic changes of deformed shapes.

CN103992631A provides a polymer material with two-way shape memory, including two interpenetrating network polymers interspersed with each other; one of the network polymers is a shape memory polymer of crystalline cross-linked polymers, and the other network The polymers are cross-linked elastic materials. The crystalline crosslinked polymer is one or more of shape memory polymers of polyurethane, polyethylene, polynorbornene, trans polyisoprene or styrene-butadiene copolymer; the crosslinked elastic material is One or more of polyurethane elastomer resin, SBS resin, propylene-butene copolymer, hard rubber or silicone rubber.

CN101560302 discloses a liquid crystal elastomer and fiber with two-way shape memory effect and a preparation method thereof. The molecular structure of the liquid crystal elastomer or fiber is one of the following two types of polymers or a mixture of two types of polymers.

CN101164770B relates to a polymer composite material with two-way shape memory effect and its preparation method, the polymer composite material comprises at least two layers of superimposed and bonded polymers, wherein at least one layer of polymers is selected from polyurethane, cross-linked A shape memory polymer material of polyethylene, polynorbornene, trans polyisoprene or styrene-butadiene copolymer, said at least two layers of superimposed bonded polymers further comprising a layer of elastic A material and/or a thin sheet of plastic capable of bending and actively recovering.

The research on two-way reversible shape memory polymers achieved a breakthrough in 2013. The Lendlein group reported the reversible shape memory function of a twin-crystal thermosetting polyurethane system with microphase separation and different thermal transition temperatures of the two phases (BehlM, Kratz K, ZotzmannJ, Lendlein A. Reversible bidirectional shape-memory polymers. Adv. Mater. 2013, 25, 4466.). But it has the following disadvantages:

1. The adjustability of the phase transition temperature is poor. The phase transition temperature of polymer crystallization can usually be adjusted in a small range by introducing a small amount of comonomer, but too much comonomer will completely destroy the crystallization. Therefore, according to the actual application It is likely that it is almost impossible to simultaneously adjust the two crystallographic phase transition temperatures over a wide range;

2. Since the polymer cannot be completely crystallized, and the crystallinity of the two phases is likely to change with the thermomechanical conditions of the reversible shape memory, the twin-crystal thermosetting system is not suitable for the quantitative mechanism research of the reversible shape memory. In contrast, the glass transition temperature of amorphous polymers can be continuously regulated in a wide range by the introduction of comonomers, and the glass transition temperature is more complete, and the glass transition temperature is relatively less sensitive to thermomechanical conditions.

Contents of the invention

According to the shortcomings of shape memory materials in the prior art, the present invention develops a polymer material with a single crystal thermosetting system and a bidirectional reversible shape memory effect. The material uses a high-temperature amorphous phase as a stress phase to realize reversible shape memory; that is The reversible deformation of the shape can be realized through the low-temperature crystalline phase in the cross-linked system as the temperature changes, and it has a two-way memory function of repeatedly memorizing the shape of two states.

The polymer with bidirectional reversible shape memory effect provided by the present invention comprises at least one amorphous phase and one crystalline phase, wherein the glass transition temperature of the amorphous phase is higher than the melting temperature of the crystalline phase, and the difference between the two is at least 20°C.

The polymer material is prepared by the following method:

(1) Select a substance that provides a high glass transition temperature;

(2) Select a crystalline substance;

(3) The above two substances are cross-linked and solidified.

Preferably, the high-temperature amorphous phase material is an acrylate with a high glass transition temperature, such as: methyl methacrylate, cyclohexyl methacrylate, tricyclodecane dimethanol diacrylate or a mixture thereof; The glass transition temperature Tg needs to be around 100°C or above, preferably the glass transition temperature Tg>95°C.

Preferably, the crystalline phase substance is selected from polyethylene glycol diacrylate, polyethylene glycol dimethacrylate or polycaprolactone diacrylate; the polyethylene glycol diacrylate or polyethylene glycol diacrylate The molecular weight range of diol dimethacrylate is 3000-12000; the molecular weight of the polycaprolactone diacrylate is 3000-14000; the Tm range is 45-65°C. The melting point of the two-way reversible shape memory effect polymer after crosslinking is 35-55 DEG C.

The polymer is a thermosetting polymer obtained by chemical crosslinking,

The glass transition temperature of the high-temperature amorphous phase and the melting temperature of the low-temperature crystalline phase of the polymer are respectively defined as T ₁ , T ₂ (T ₁ >T ₂ ), defined as T _high >T ₁ >T _middle >T ₂ >T _low , heat the material to T _high , apply a certain external force to deform it, and remove the external force after cooling to T _middle , and mark the fixed shape of the material as Shape A (the first deformation). In the absence of external force, the material continues to cool (T _middle drops to T _low ) causing Shape A to change to Shape B (the second deformation). Afterwards, when the temperature changes multiple times between T _middle and T _low (without external force), the shape of the material can change reversibly between A and B accordingly.

The two-way reversible shape function of the polymer can realize the two-phase ratio, crosslink density, melting temperature of the crystalline phase and vitrification of the amorphous phase under the premise that the glass transition temperature of the amorphous phase is higher than the melting temperature of the crystalline phase Temperature regulation.

Preferably, the two-way reversible shape memory function of the polymer material is realized through changes in external conditions, and the external conditions, such as transition temperature, are mainly determined by the melting temperature of the low-temperature crystalline phase in the polymer.

The principle of the present invention is that by heating the polymer above the glass transition temperature of the high-temperature amorphous phase, the first deformation process caused by applying a certain external force can not only determine the first Shape A of the polymer, but also provide The internal stress required to make the second deformation reversible. The driving force for the reversibility of the second deformation is the reversible orientation of the low-temperature crystal phase under the action of the internal stress as the temperature changes. Although the first deformation is irreversible, the shape A can be changed programmatically through this process, and the change will lead to the change of shape B accordingly.

The innovation of the present invention lies in that it proposes to replace the high-temperature crystalline phase with a high-temperature amorphous phase as a stress phase to realize reversible shape memory, thereby preparing single-crystal thermosetting reversible shape-memory polymers; and realizing the adjustability of phase transition temperature.

The prepared shape memory polymer has the following advantages:

1) The shape memory polymer has a two-way reversible memory effect, good stability, and can change back and forth between two shapes through external stimuli;

2) There are sufficient raw materials to choose from, and multiple different systems can be designed according to the selected raw materials;

3) The phase transition temperature of shape memory polymers is highly adjustable;

4) The shape memory polymer is light in weight;

5) The preparation method of the shape memory polymer is simple, and can be designed into different shapes according to actual needs;

6) Shape memory polymers are cheap;

7) Shape memory polymers have good electrical insulation properties and thermal insulation effects.

The bidirectional reversible shape memory polymer material prepared by the invention has important application prospects, and has great potential application value in the fields of biomedicine, textile materials, machinery manufacturing, electronic equipment, cable industry, packaging industry and the like.

Description of drawings

Fig. 1 is the DMA test graph of the polymer obtained in Example 1.

Fig. 2 is a graph showing the characterization results of the double shape memory after the programmed shaping in Example 1.

FIG. 3 is a DMA test graph of the polymer obtained in Example 2. FIG.

Fig. 4 is a graph showing the characterization results of the double shape memory after the programmed shaping in Example 2.

FIG. 5 is a DMA test graph of the polymer obtained in Example 3. FIG.

Fig. 6 is a graph showing the characterization results of the double shape memory after the programmed shaping in Example 3.

FIG. 7 is a DMA test chart of the polymer obtained in Example 4. FIG.

Fig. 8 is a graph showing the characterization results of the double shape memory after the programmed shaping in Example 4.

FIG. 9 is a graph showing the repeatability and stability test results of the double shape memory of the polymer obtained in Example 4. FIG.

Detailed ways

The present invention will be further described below in conjunction with the examples, but the protection scope of the present invention is not limited to the scope expressed by the examples.

Example 1

raw material:

a) polyethylene glycol diacrylate (PEGDA): Mw=8000, Alfa Aesar company;

b) Cyclohexyl methacrylate (CMA): Sigma-Aldrich;

c) Benzoyl peroxide (BPO): Aladdin Reagent (Shanghai) Co., Ltd.;

Preparation:

Prepared by bulk polymerization: weigh a certain amount of polyethylene glycol diacrylate and cyclohexyl methacrylate (the mass ratio of PEGDA to CMA is 3:1), add benzoyl peroxide (the amount of which is the system 3% of the total mass), dissolved at 70°C, stirred evenly, poured into a sealed glass tank, and cured at 100°C for 2 to 3 hours. The DMA test results of the crystalline melting temperature and glass transition temperature of the obtained polymer are shown in Fig. 1 .

Characterization of double shape memory: heat the polymer to 156°C, apply a force of 1N to stretch it, cool it to 56°C under this tension, and remove the tension. This process is a programmed deformation process. Then continue to lower the temperature to 0°C and raise the temperature to 56°C. The polymer can repeat the double shape memory phenomenon of cold elongation and heat shrinkage at 0°C to 56°C. The results are shown in Figure 2.

Example 2

raw material:

d) Polyethylene glycol diacrylate (PEGDA): Mw=8000, Alfa Aesar company;

e) Cyclohexyl methacrylate (CMA): Sigma-Aldrich;

f) tricyclodecane dimethanol diacrylate (TDD): Sigma-Aldrich company;

g) Benzoyl peroxide (BPO): Aladdin Reagent (Shanghai) Co., Ltd.;

Preparation:

Prepared by bulk polymerization: weigh a certain amount of polyethylene glycol diacrylate, cyclohexyl methacrylate and tricyclodecane dimethanol diacrylate (wherein the mass ratio of PEGDA to CMA and TDD is 6:1:2 ), add benzoyl peroxide (the addition amount is 3% of the total mass of the system), dissolve it at 70°C, stir evenly, pour it into a sealed glass tank, and solidify at 100°C for 2-3h. The DMA test results of the crystalline melting temperature and glass transition temperature of the obtained polymer are shown in Fig. 3 .

Characterization of double shape memory: heat the polymer to 170°C, apply a force of 2N to stretch it, cool it to 56°C under this tension, and remove the tension. This process is a programmed deformation process. Then continue to lower the temperature to 0°C and raise the temperature to 56°C. The polymer can repeat the double shape memory phenomenon of cold elongation and heat shrinkage at 0°C to 56°C. The results are shown in Figure 4.

Example 3

raw material:

h) polyethylene glycol diacrylate (PEGDA): Mw=8000, Alfa Aesar company;

i) cyclohexyl methacrylate (CMA): Sigma-Aldrich company;

j) Benzoyl peroxide (BPO): Aladdin Reagent (Shanghai) Co., Ltd.;

Preparation:

Prepared by bulk polymerization: weigh a certain amount of polyethylene glycol diacrylate and cyclohexyl methacrylate (wherein the mass ratio of PEGDA to CMA is 2:1), add benzoyl peroxide (the amount added is the total amount of the system) 3% of the mass), dissolve it at 70°C, stir it evenly, pour it into a sealed glass tank, and cure it at 100°C for 2 to 3 hours. The DMA test results of the crystalline melting temperature and glass transition temperature of the obtained polymer are shown in Fig. 5 .

Characterization of double shape memory: heat the polymer to 170°C, apply a force of 2N to stretch it, cool it to 56°C under this tension, and remove the tension. This process is a programmed deformation process. Then continue to cool down to 0°C and raise the temperature to 56°C. The polymer can repeat the double shape memory phenomenon of cold elongation and heat shrinkage at 0°C to 56°C. The results are shown in Figure 6.

Example 4

raw material:

k) polyethylene glycol diacrylate (PEGDA): Mw=8000, Alfa Aesar company;

l) Cyclohexyl methacrylate (CMA): Sigma-Aldrich;

m) tricyclodecane dimethanol diacrylate (TDD): Sigma-Aldrich company;

n) Benzoyl peroxide (BPO): Aladdin Reagent (Shanghai) Co., Ltd.;

Preparation:

Prepared by bulk polymerization: weigh a certain amount of polyethylene glycol diacrylate, cyclohexyl methacrylate and tricyclodecane dimethanol diacrylate (wherein the mass ratio of PEGDA to CMA and TDD is 12:1:2 ), add benzoyl peroxide (the addition amount is 3% of the total mass of the system), dissolve it at 70°C, stir evenly, pour it into a sealed glass tank, and solidify at 100°C for 2-3h. The DMA test results of the crystalline melting temperature and glass transition temperature of the obtained polymer are shown in Fig. 7 .

Characterization of double shape memory: heat the polymer to 170°C, apply a force of 2N to stretch it, cool it to 56°C under this tension, and remove the tension. This process is a programmed deformation process. Then continue to cool down to 0°C and raise the temperature to 56°C. The polymer can repeat the double shape memory phenomenon of cold elongation and heat shrinkage at 0°C to 56°C. The results are shown in Figure 8. Repeating the above multiple times characterizes the repeatability and stability of the double shape memory, and the results are shown in FIG. 9 .

Claims (7)

1. have a polymkeric substance for bidirectional reversible shape memory effect, it is characterized in that: this polymkeric substance comprises at least one amorphous phase and a crystallization phases, wherein the second-order transition temperature of amorphous phase is higher than the melt temperature of crystallization phases, and both at least differ 20 DEG C.

2. the polymkeric substance with bidirectional reversible shape memory effect according to claim 1, is characterized in that: the described material of high glass-transition temperature that provides is acrylate.

3. the polymkeric substance with bidirectional reversible shape memory effect according to claim 2, is characterized in that: described acrylate is methyl methacrylate, cyclohexyl methacrylate, Tricyclodecane Dimethanol diacrylate or its mixture.

4. the polymkeric substance with bidirectional reversible shape memory effect according to claim 1, is characterized in that: the fusing point of described crystal material is at 45 ~ 65 DEG C, and the fusing point of crosslinked post-consumer polymer is at 35 ~ 55 DEG C.

5. the polymkeric substance with bidirectional reversible shape memory effect according to claim 4, is characterized in that: described crystal material is selected from polyethyleneglycol diacrylate, polyethylene glycol dimethacrylate or polycaprolactone diacrylate.

6. the polymkeric substance with bidirectional reversible shape memory effect according to claim 5, is characterized in that: described polyethyleneglycol diacrylate or the molecular weight ranges of polyethylene glycol dimethacrylate are 3000 ~ 12000; The molecular weight of described polycaprolactone diacrylate is 3000 ~ 14000.

7., according to the arbitrary described preparation method with the polymkeric substance of bidirectional reversible shape memory effect of claim 1-6, it is characterized in that, described polymkeric substance is prepared by the following method:

(1) a kind of material that high glass-transition temperature is provided is selected; Its glass transition temperature Tg >95 DEG C;

(2) select a kind of crystal material, its fusing point is at 45 ~ 65 DEG C;

(3) by above-mentioned two kinds of material crosslinking curings.