Polydicyclopentadiene thermotropic shape memory material with excellent heat resistance as well as preparation method and application of polydicyclopentadiene thermotropic shape memory material

Abstract

The invention relates to a polydicyclopentadiene thermotropic shape memory material with excellent heat resistance and a preparation method and application thereof.The polydicyclopentadiene thermotropic shape memory material is obtained by conducting ring-opening metathesis polymerization on dicyclopentadiene under catalysis of a Grubbs second-generation catalyst, the Tg of the polydicyclopentadiene thermotropic shape memory material ranges from 136 DEG C to 164 DEG C, the gel content ranges from 95.21% to 98.97%, the shape fixing rate at 220 DEG C is larger than or equal to 97%, and the polydicyclopentadiene thermotropic shape memory material has excellent heat resistance. The shape recovery rate is greater than or equal to 95%, and the shape recovery rate reaches 95% or above within 10 min at the temperature of 220 DEG C. The polydicyclopentadiene thermotropic shape memory material provided by the invention is high in Tg temperature, good in heat resistance, good in shape memory performance and relatively low in cost, the application range of the thermotropic shape memory material can be expanded, and the polydicyclopentadiene thermotropic shape memory material has good economic value.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic polymer compounds, and particularly relates to a poly(dicyclopentadiene) thermally induced shape memory material with excellent heat resistance, and a preparation method and application thereof. Background Art

[0002] Smart materials are a current research hotspot, and shape memory materials (SMMs) are an important branch among them. Shape memory materials refer to materials with a certain initial shape that can be deformed under certain external conditions and fixed into another temporary shape, and then can be restored to the initial shape through physical stimuli such as heat, light, electricity, magnetism or chemical stimuli.

[0003] According to different response methods, shape memory materials can be divided into thermally induced type, photoinduced type, electroinduced type, magnetoinduced type and chemically induced type. Among them, thermally induced shape memory materials are the most widely and deeply studied shape memory materials at present. Among many thermally induced shape memory materials, thermally induced shape memory polymers have great application prospects in the fields of aerospace, biomedicine, flexible electronic devices, 4D printing and packaging engineering due to their advantages such as light weight, large flexibility, large deformability, good corrosion resistance and simple processing conditions.

[0004] Regarding the working mechanism of thermally induced shape memory polymers, it is generally considered to be related to the glass transition temperature T g of the polymer. In the structure of thermally induced shape memory polymers, there are two phases, namely a fixed phase that remembers the initial shape and a reversible phase that can be reversibly cured and softened with temperature change. When the temperature is below the glass transition temperature, the polymer is in a glassy state and the polymer chain segments are frozen; when the temperature is higher than T g , the chain segments start to move and the polymer is in a highly elastic state. At this time, an external force is applied to deform the reversible phase of the material to the temporary shape, and then the external force is maintained to keep the deformation. Then the temperature is lowered to T g or below, and the molecular chain segments are frozen again, and the temporary shape given to the material is retained. Once the temperature reaches T gAbove, the molecular chain segments are thawed and begin to move. Under the action of the stationary phase, they gradually return to their initial shape. Tian et al. mixed thermoplastic polyimide (TPI) and paraffin in a mixer, heated them while adding a crosslinking agent to cause vulcanization crosslinking of TPI, and obtained a TPI-crosslinked TPI / paraffin polymer material. Due to the large difference in the melting temperature and crystallization temperature between TPI and paraffin, the polymer material exhibits triple shape memory behavior, and its shape memory behavior can be adjusted by changing the crosslinking density of TPI and the crystallinity of paraffin or TPI (TIAN M, et al. ACS Applied Materials & Interfaces, 2020, 12(5): 6426-6435). The shape memory performance of the material was tested at 75°C, 37°C, and 0°C. When the material reached different deformation temperatures, it could quickly return to the shape it remembered at that time, showing good deformation ability. Sayan et al. synthesized a new type of semi-crystalline shape memory polymer from polybutadiene and octadecyl acrylate. By adjusting the process parameters, the optimized sample showed excellent shape memory performance at room temperature (BASAK S, CAVICCHI KA. Macromolecular Rapid Communications, 2023, 44(1): 2200404).

[0005] However, at present, most thermally induced shape memory polymers have a low usable temperature range due to the influence of the thermal properties of the materials themselves, and they still cannot meet the requirements for use in high-temperature environments in fields such as aerospace, new energy, and national defense. Therefore, preparing high-temperature-resistant shape memory polymers is a major challenge at this stage.

[0006] The present invention is based on dicyclopentadiene (DCPD) in the C 5 fraction by-produced from ethylene production by petroleum cracking to prepare a poly(dicyclopentadiene) thermally induced shape memory material with excellent heat resistance, expanding the application scenarios of shape memory materials. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide, in view of the deficiencies in the prior art, a poly(dicyclopentadiene) thermally induced shape memory material with excellent heat resistance, and its preparation method and application.

[0008] The present invention provides a poly(dicyclopentadiene) thermally induced shape memory material with excellent heat resistance. The poly(dicyclopentadiene) thermally induced shape memory material is obtained by ring-opening metathesis polymerization (ROMP) of dicyclopentadiene catalyzed by the second-generation Grubbs catalyst. Its Tg is 136 - 164 °C, the gel content is 95.21 - 98.97%, the shape fixation rate is ≥97% at 220 °C, the shape recovery rate is ≥95%, and the shape recovery rate reaches more than 95% within 10 min at 220 °C (the material is heated and deformed at 160 - 220 °C and then cooled and fixed at 25 °C for measurement).

[0009] The present invention also provides a preparation method of the above-mentioned poly(dicyclopentadiene) thermally induced shape memory material with excellent heat resistance. The specific steps are as follows: Heat dicyclopentadiene until it melts, then add the second-generation Grubbs catalyst, and after mixing evenly, carry out ring-opening metathesis polymerization to obtain the poly(dicyclopentadiene) thermally induced shape memory material with excellent heat resistance.

[0010] Its reaction route is as follows:

[0011]

[0012] According to the above scheme, the heating and melting temperature of dicyclopentadiene is 50 - 70 °C.

[0013] According to the above scheme, the structural formula of the second-generation Grubbs catalyst is:

[0014]

[0015] According to the above scheme, the mass ratio of dicyclopentadiene to the second-generation Grubbs catalyst is 1:1 - 5‰.

[0016] According to the above scheme, dicyclopentadiene and the second-generation Grubbs catalyst are mixed evenly by a mixer. The rotation speed of the mixer is 2000 - 3000 r / min, and the mixing time is 30 - 60 s.

[0017] According to the above scheme, the process conditions for ring-opening metathesis polymerization are: reacting at 60 - 80 °C for 1 - 4 min.

[0018] The present invention also includes the application of the above-mentioned poly(dicyclopentadiene) thermally induced shape memory material with excellent heat resistance in the field of intelligent materials.

[0019] The beneficial effects of the present invention are as follows: 1. The poly(dicyclopentadiene) thermally induced shape memory material provided by the present invention has a high Tg temperature, good heat resistance, good shape memory performance, and low cost, which can expand the application range of thermally induced shape memory materials and has good economic value; 2. The present invention is based on the C by-product of ethylene production from petroleum cracking 5The preparation of poly(dicyclopentadiene) thermally induced shape memory materials from dicyclopentadiene in the fraction has mild reaction conditions, is obtained through a one-step reaction, requires no post-treatment, has simple steps, and is suitable for industrial production. Description of the Drawings

[0020] Figure 1 This is the infrared spectrum comparison diagram of PDCPD prepared in Example 5 of the present invention and the raw material DCPD.

[0021] Figure 2 This is the comparison diagram of the gel content of PDCPD obtained under different catalyst dosages in Examples 1-5.

[0022] Figure 3 This is the DSC test diagram of the PDCPD samples prepared in Examples 1-5.

[0023] Figure 4 This is the comparison diagram of the TGA curves of the PDCPD samples prepared in Examples 1-5.

[0024] Figure 5 This is the comparison diagram of the DTG curves of the PDCPD samples prepared in Examples 1-5.

[0025] Figure 6 This is the stress-strain curve diagram of the tensile test of the PDCPD samples prepared in Examples 1-5.

[0026] Figure 7 This is the test photo of the weight lifting of the spline prepared from PDCPD in Example 3.

[0027] Figure 8 This is the stress-strain curve diagram of the bending test of the PDCPD samples prepared in Examples 1-5.

[0028] Figure 9 This is the bending test photo of the spline prepared from PDCPD in Example 3.

[0029] Figure 10 This is the photo of the deformation fixation and recovery process of the spline prepared from PDCPD in Example 3.

[0030] Figure 11 This is the comparison diagram of the change in the shape fixation rate and recovery rate of PDCPD splines with different catalyst contents in Examples 1-5 under different temperature scenarios.

[0031] Figure 12 This is the shape recovery comparison diagram of PDCPD obtained in Examples 1-5 at 140 °C, 180 °C, and 220 °C. Detailed Embodiments

[0032] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to embodiments and the accompanying drawings.

[0033] Example 1

[0034] A poly(dicyclopentadiene) thermally induced shape memory material with excellent heat resistance is prepared as follows: Place dicyclopentadiene in an electrothermal constant temperature blast drying oven at 60 °C and heat it to a liquid state. Take 5.11 g of liquid dicyclopentadiene and add it to a centrifuge tube. Then add 0.0057 g of Grubbs second-generation catalyst (the mass ratio of dicyclopentadiene to Grubbs second-generation catalyst is 1:1‰) to the centrifuge tube. Use a mixer (SCI-VS adjustable mixer from Czech company Selo in the United States) to mix evenly. The rotation speed of the mixer is 2500 r / min, and the mixing time is 30 s. Then pour it into straight bar-shaped and dumbbell-shaped molds, remove the air bubbles in the molds, and transfer it to an electrothermal constant temperature blast drying oven at 60 °C for reaction. The reaction time is 3 min 26 s. After the reaction is completed, a sample (denoted as PDCPD-1) is obtained.

[0035] Example 2

[0036] A poly(dicyclopentadiene) thermally induced shape memory material with excellent heat resistance is prepared in a similar manner to Example 1, except that: the amount of liquid dicyclopentadiene added is 5.03 g, the amount of Grubbs second-generation catalyst added is 0.0101 g (the mass ratio of dicyclopentadiene to Grubbs second-generation catalyst is 1:2‰), the reaction time is 2 min 27 s, and the obtained sample is denoted as PDCPD-2.

[0037] Example 3

[0038] A poly(dicyclopentadiene) thermally induced shape memory material with excellent heat resistance is prepared in a similar manner to Example 1, except that: the amount of liquid dicyclopentadiene added is 5.50 g, the amount of Grubbs second-generation catalyst added is 0.0163 g (the mass ratio of dicyclopentadiene to Grubbs second-generation catalyst is 1:3‰), the reaction time is 1 min 47 s, and the obtained sample is denoted as PDCPD-3.

[0039] Example 4

[0040] A poly(dicyclopentadiene) thermally induced shape memory material with excellent heat resistance is prepared in a similar manner to Example 1, except that: the amount of liquid dicyclopentadiene added is 5.01 g, the amount of Grubbs second-generation catalyst added is 0.0210 g (the mass ratio of dicyclopentadiene to Grubbs second-generation catalyst is 1:4‰), the reaction time is 1 min 25 s, and the obtained sample is denoted as PDCPD-4.

[0041] Example 5

[0042] A poly(dicyclopentadiene) thermally induced shape memory material with excellent heat resistance, its preparation method is similar to that of Example 1, the differences are as follows: the addition amount of liquid dicyclopentadiene is 5.05 g, the addition amount of Grubbs second-generation catalyst is 0.0255 g (the mass ratio of dicyclopentadiene to Grubbs second-generation catalyst is 1:5‰), the reaction time is 1 min 15 s, and the obtained sample is denoted as PDCPD-5.

[0043] Test the properties of the poly(dicyclopentadiene) thermally induced shape memory materials prepared in Examples 1 - 5:

[0044] Infrared spectroscopy (FT-IR) test: Use a Nicolet iS50 Fourier transform infrared spectrometer from Thermo Fisher Scientific to perform infrared spectroscopy tests. For the liquid DCPD sample (obtained by melting dicyclopentadiene into a liquid), the total reflection test is carried out by the film coating method; for the solid PDCPD sample, it is ground into powder, potassium bromide (KBr) is used as the dispersant, and a tablet is prepared for transmission test. The scanning wavenumber range is 4000 - 500 cm -1 . As Figure 1 shown is the infrared spectrum comparison chart of PDCPD prepared in Example 5 and the raw material DCPD. It can be found that at the wavenumbers of 3003 cm -1 and 972 cm -1 , new absorption peaks appear on the PDCPD curve. The peak at 3003 cm -1 belongs to the stretching vibration peak of the C-H bond in the non-cyclic olefin structure, and the peak at 972 cm -1 belongs to the deformation vibration peak of the C-H bond in the non-cyclic olefin structure. These characteristic signals indicate that after DCPD polymerizes into PDCPD, non-cyclic olefin structural units appear in the structure, proving that the ROMP reaction has occurred. At 3050 cm -1 , strong absorption peaks appear on both the DCPD and PDCPD curves. This peak belongs to the stretching vibration absorption peak of the =C-H carbon-hydrogen bond in the cyclic olefin, indicating that a large number of cyclopentene rings are still retained in PDCPD, which conforms to the characteristics of ROMP; compared with the DCPD curve, the absorption peak at 1620 cm -1 and the absorption peak at 1570 cm -1 on the PDCPD curve show an increasing and decreasing trend respectively. These two peaks belong to the stretching vibration peak of the non-cyclic C=C bond and the stretching vibration peak of the cyclic C=C bond, which also proves that PDCPD has been successfully polymerized.

[0045] Gel content test: Weigh the samples prepared in Examples 1-5, record their original mass, and immerse them separately in a good solvent (acetone). Take them out every two days, dry them and weigh their remaining mass until the mass remains stable. The ratio of the remaining mass to the original mass is the gel content of PDCPD, which can reflect the conversion rate of DCPD. As Figure 2 shown in the comparison chart of the gel content of PDCPD obtained under different catalyst dosages in Examples 1-5, it can be seen that as the catalyst dosage increases, the gel content of PDCPD shows an upward trend. When the catalyst dosage is 5‰, the gel content of the sample can reach 98.97%.

[0046] DSC test: Use a differential scanning calorimeter (DSC) to test the glass transition temperature (Tg) of the PDCPD samples prepared in Examples 1-5. The test results are as Figure 3 shown. It can be seen that the Tg of PDCPD with a catalyst dosage of 1‰ is about 136.0 °C. As the catalyst dosage increases, the glass transition temperature (Tg) of PDCPD shows an upward trend. When the catalyst content is 5‰, its Tg rises to about 160 °C.

[0047] Thermogravimetric analysis: The TGA curves and DTG curves of the PDCPD samples prepared in Examples 1-5 are as Figure 4 and Figure 5 shown. From the figure, the temperatures T d5％ 、T d10％ 、T d50％ at which the samples lose 5%, 10%, and 50% of their weight can be obtained and are listed in Table 1 below.

[0048] Table 1

[0049]

[0050] It can be seen from the thermal decomposition curve (TGA curve) that for PDCPD obtained with different catalyst dosages, the change trend of the weight loss curve is roughly the same. It can be seen from the DTG curve that the thermal decomposition process of the sample is mainly concentrated in two temperature ranges. First, a small thermal weight loss peak appears in the range of 200-300 °C, which is caused by a small amount of unreacted DCPD monomers or low molecular weight polymers in the system. A large thermal weight loss plateau appears in the range of 420-500 °C, which is due to the thermal decomposition of PDCPD. Most of the mass lost by the sample occurs in this temperature range, indicating that the thermal decomposition temperature of the PDCPD sample is above 420 °C, showing excellent high temperature resistance.

[0051] Tensile property test: The stress-strain curves of the tensile tests of the PDCPD samples prepared in Examples 1-5 are as Figure 6As shown, it can be seen that as the catalyst dosage increases from 1‰ to 5‰, the tensile strength of PDCPD shows a trend of first increasing and then decreasing. When the catalyst dosage increases from 1‰ to 3‰, the tensile strength of the PDCPD spline shows an increasing trend, reaching a maximum of 51.0 MPa. When the catalyst dosage continues to increase, the tensile strength of the PDCPD spline begins to decrease. This may be because when the catalyst dosage is relatively large, the crosslinking degree of the spline is relatively large, and the relative movement space of the chain segments is relatively small. When subjected to an external force, the internal chain segments cannot move freely, and its fracture strain also shows a decreasing trend. A weight-lifting demonstration was carried out on the spline (with a straight section length of 20.0 mm, a width of 4.0 mm, and a thickness of 2.0 mm) prepared from the PDCPD of Example 3. It was able to lift a heavy object with a mass of 5 kg, and no fracture or cracking occurred in the spline. The test photos are as Figure 7 shown.

[0052] Flexural property test: The stress-strain curves of the PDCPD samples prepared in Examples 1-5 during the flexural test are as Figure 8 shown. It can be seen that the trend of its flexural properties is consistent with the tensile properties. As the catalyst dosage increases, the crosslinking degree of the spline increases, and the space for the molecular chain segments to move freely under the action of an external force decreases. Therefore, it shows a trend of first increasing and then decreasing in flexural strength. This indicates that an appropriate degree of crosslinking helps to balance the comprehensive mechanical properties of the PDCPD spline. In addition, a flexural demonstration was carried out on the spline prepared from the PDCPD of Example 3. The test photos are shown in Figure 9 . At a relatively large flexural angle, no fracture or cracking occurred in the spline, indicating that PDCPD still has a certain toughness at a relatively high Tg temperature.

[0053] The shape memory behavior of the PDCPD splines prepared in Examples 1-5 was tested. The test method is as follows: The PDCPD splines of Examples 1-5 were heated at a certain temperature (160 °C, 180 °C, 200 °C, 220 °C, and each example sample was tested at each temperature) for 20 min, and then an external force was quickly applied to cause a 90° deformation. Under the state of maintaining the external force, it was quickly cooled to room temperature to fix it, and the fixed angle θ f was measured after removing the external force. Finally, the spline was heated again to allow it to spontaneously recover, and the angle θ r after recovery was measured. The shape fixation rate (R f ) and shape recovery rate (R r ) were calculated according to the following formula:

[0054]

[0055] The photos of the deformation fixation and recovery process of the spline prepared from the PDCPD of Example 3 are as Figure 10 shown. The change trends of the shape fixation rate and recovery rate of the PDCPD splines with different catalyst contents in Examples 1-5 under different temperature scenarios are asFigure 11 As shown, it can be seen that with the increase in temperature, the fixation rate and recovery rate of each PDCPD sample show an upward trend. Through DSC testing, it is known that the glass transition temperatures T of PDCPD with catalyst dosages of 1‰ and 2‰ are 136.0 °C and 149.4 °C respectively. Therefore, at the tested temperatures, the polymer segments are in a "thawed" state, and their fixation and recovery show good performance, with a relatively small trend of change with temperature. For PDCPD with catalyst dosages of 3‰ - 5‰, its crosslinking degree is higher and the glass transition temperature is higher. At 160 °C, the polymer segments are not completely in a "thawed" state. Therefore, at this temperature, its fixation rate and recovery rate are not as good as those of PDCPD with catalyst dosages of 1‰ and 2‰. However, with the increase in temperature, the segmental motion becomes more active, and the shape recovery rate and recovery rate are improved. The shape fixation rates of the PDCPD splines prepared in Examples 1 - 5 at 220 °C are 97.8 - 100%, and the shape recovery rates are 95.4 - 100%. g Due to the different glass transition temperatures of the PDCPD obtained in Examples 1 - 5 with different catalyst dosages, they show different recovery behaviors at different temperatures. The recovery trends at 140 °C, 180 °C, and 220 °C are shown in

[0056] ... It can be seen that at 140 °C, only the PDCPD spline with a catalyst dosage of 1‰ exhibits a recovery behavior. This is because only the glass transition temperature of this spline is lower than 140 °C, and for other splines, since the temperature has not reached their T Figure 12 above, the molecular chains are not thawed, so no recovery occurs. When the temperature rises to 180 °C, each spline shows a recovery behavior, but due to the different T g values, at this time, each spline shows different recovery degrees. At 220 °C, since the scene temperature is greater than the T g of the splines, each spline shows good recovery behavior (shape fixation rate ≥ 97%, shape recovery rate ≥ 95%). It can also be seen that with the increase in the scene temperature, the recovery rate of PDCPD shows an increasing trend. At 220 °C, the shape recovery rates of all samples reach more than 95% within 10 minutes. g ​

Claims

1. A polydicyclopentadiene thermal shape memory material with excellent heat resistance, characterized in that: The polydicyclopentadiene thermal shape memory material is obtained by ring-opening metathesis polymerization of dicyclopentadiene catalyzed by a Grubbs second-generation catalyst, and has a Tg of 136-164° C., a gel content of 95.21-98.97%, a shape fixation rate of ≥97% at 220° C., a shape recovery rate of ≥95%, and a shape recovery rate of more than 95% within 10 minutes at 220° C.

2. A method for preparing the polydicyclopentadiene thermal shape memory material with excellent heat resistance as claimed in claim 1, characterized in that: The specific steps are as follows: heating and melting dicyclopentadiene, then adding Grubbs second-generation catalyst, mixing evenly and then performing ring-opening metathesis polymerization to obtain polydicyclopentadiene thermal shape memory material with excellent heat resistance.

3. The method for preparing the polydicyclopentadiene thermal shape memory material with excellent heat resistance according to claim 2, characterized in that: The heating melting temperature of dicyclopentadiene is 50-70℃.

4. The method for preparing the polydicyclopentadiene thermal shape memory material with excellent heat resistance according to claim 2, characterized in that: The structural formula of the Grubbs second generation catalyst is:

5. The method for preparing the polydicyclopentadiene thermal shape memory material with excellent heat resistance according to claim 2, characterized in that: The mass ratio of dicyclopentadiene to Grubbs second generation catalyst is 1:1-5‰.

6. The method for preparing the polydicyclopentadiene thermal shape memory material with excellent heat resistance according to claim 2, characterized in that: The dicyclopentadiene and the Grubbs second-generation catalyst are uniformly mixed using a mixer, the mixer speed is 2000-3000 r / min, and the mixing time is 30-60 s.

7. The method for preparing the polydicyclopentadiene thermal shape memory material with excellent heat resistance according to claim 2, characterized in that: The process conditions of the ring-opening metathesis polymerization are: reacting at 60-80°C for 1-4 minutes.

8. Application of the polydicyclopentadiene thermo-induced shape memory material with excellent heat resistance as claimed in claim 1 in the field of smart materials.

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