Comonomer for directly preparing high polymer material by olefin metathesis polymerization and preparation method thereof

Abstract

The invention provides a comonomer for directly preparing a high polymer material through olefin metathesis polymerization, the comonomer takes norbornene as an end-capping group, and the structure of the comonomer is as shown in the following formulas M1-M3: # imgabs0 #. The invention also provides a preparation method of the comonomer, a structural monomer directly prepared from the comonomer through olefin metathesis polymerization, and a high polymer material.

Description

Technical Field

[0001] The present invention relates to the field of polymer material synthesis, and in particular to a comonomer for directly preparing polymer materials by olefin metathesis polymerization and a preparation method thereof. Background Art

[0002] With the rapid development of modern science and technology, all walks of life have increasingly stringent requirements on the performance of polymer materials. Although polymer materials obtained by traditional preparation methods have excellent performance in some aspects, it is often difficult to achieve excellent levels in multiple key performance indicators such as strength, toughness, thermal stability and recyclability. This limitation greatly restricts the wide application of polymer materials in high-end manufacturing, environmental protection and energy saving, medical health and other fields.

[0003] Finding suitable structural monomers and suitable preparation methods is a complex and challenging process that requires interdisciplinary knowledge and technical support. Finding suitable structural monomers and suitable preparation methods among many compounds is of far-reaching significance. The synthesis of polymer materials usually involves many complex chemical reactions, such as polymerization, addition, condensation, etc. These reactions require precise control of conditions such as temperature, pressure, and reactant ratio. Any slight error may lead to poor product performance or even synthesis failure. This complexity increases the difficulty and uncertainty of synthesizing polymer materials. In addition, a large amount of solvents, catalysts and other substances are usually used in the synthesis process of polymer materials. These substances are often difficult to completely recover and dispose of after the reaction, thus causing pollution to the environment. In addition, some polymer materials may also release harmful substances during use, posing a threat to the environment and human health.

[0004] Therefore, how to find suitable synthetic monomers and design scientific and reasonable preparation methods to achieve green synthesis and sustainable development of polymer materials is one of the important challenges currently faced. Summary of the invention

[0005] In view of this, in order to solve at least one technical problem in the related art and other aspects, the present disclosure proposes a comonomer for directly preparing a polymer material by olefin metathesis polymerization, characterized in that the comonomer uses a norbornene group as a capping group, and the structure of the comonomer is shown in the following formulas M1 to M3:

[0006] .

[0007] In another aspect of the present disclosure, a method for preparing the aforementioned comonomer is also proposed, comprising:

[0008] Dissolving a compound represented by the following formula A and a compound represented by the following formula B or C in a toluene solvent, and reacting them at a first temperature to obtain a comonomer M1 or a comonomer M2; or,

[0009] Dissolving a compound represented by the following formula D and a compound represented by the following formula E in an N,N-dimethylimidamide solvent, and reacting them at a first temperature to obtain a comonomer M3;

[0010] .

[0011] According to an embodiment of the present disclosure, the molar ratio of compound A to compound B or compound C is 1:2; the molar ratio of compound D to compound E is 1:2; and the first temperature is 70-80°C.

[0012] In another aspect of the present disclosure, a structural monomer of a polymer material directly prepared by olefin metathesis polymerization is also provided. The structural monomer is shown in the following formula (I):

[0013] , formula (I);

[0014] Wherein, X is selected from a borate group or a maleimide group; Y is selected from a C1-C6 alkane, a C1-C6 cycloalkane, a C1-C8 cycloalkene; and m and n are independently selected from integers within the range of 100-1000.

[0015] According to an embodiment of the present disclosure,

[0016] X is selected from or Group; Y is selected from , or Group.

[0017] According to an embodiment of the present disclosure, the structural monomer is as shown in the following formulas (I-1) to (I-3):

[0018] .

[0019] According to an embodiment of the present disclosure, the polymer material includes a thermoplastic material, a thermosetting material and an elastomeric material.

[0020] In another aspect of the present disclosure, a method for directly preparing a polymer material by olefin metathesis polymerization is also proposed, comprising:

[0021] The aforementioned comonomer is mixed with a cycloolefin monomer, and a metathesis catalyst is added under oil bath conditions to cause a metathesis polymerization reaction to obtain the aforementioned structural monomer; wherein the cycloolefin monomer includes any one of dicyclopentadiene, norbornene and cyclooctene.

[0022] According to an embodiment of the present disclosure, the oil bath temperature is 40-45°C.

[0023] According to an embodiment of the present disclosure, the metathesis catalyst is a Grignard catalyst.

[0024] According to an embodiment of the present disclosure, the comonomer uses norbornene as an end-capping group. Norbornene has a unique chemical structure and reactivity, which enables this comonomer to exhibit reactivity during olefin metathesis polymerization. Using this comonomer for olefin metathesis polymerization helps to simplify the polymerization process, improve polymerization efficiency, and reduce the generation of by-products. Further, by reacting it with dicyclopentadiene (DCPD) or norbornene (NB) or cyclooctene (COE) monomers to undergo olefin ring-opening metathesis polymerization. Among them, the monomers of cyclic olefins form chain-like polymers through the breaking and recombination of double bonds, while retaining the double bonds in the monomers as dynamic covalent bonds, and obtaining a thermoplastic, thermosetting and elastomeric polymer material in one step. This polymer material has excellent mechanical, self-healing and recyclable properties, and meets the requirements of green environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is the H NMR spectrum of the comonomer M1 prepared in Example 1-1 of the present disclosure;

[0026] Figure 2 is the NMR carbon spectrum of the comonomer M1 prepared in Example 1-1 of the present disclosure;

[0027] Figure 3 is the mass spectrum of comonomer M1 prepared in Example 1-1 of the present disclosure;

[0028] Figure 4 is the H NMR spectrum of the comonomer M2 prepared in Example 1-2 of the present disclosure;

[0029] Figure 5 is the NMR carbon spectrum of the comonomer M2 prepared in Example 1-2 of the present disclosure;

[0030] Figure 6 is the mass spectrum of comonomer M2 prepared in Example 1-2 of the present disclosure;

[0031] Figure 7 is the H NMR spectrum of the comonomer M3 prepared in Examples 1-3 of the present disclosure;

[0032] Figure 8 is the NMR carbon spectrum of the comonomer M3 prepared in Examples 1-3 of the present disclosure;

[0033] Fig. 9 is the mass spectrum of comonomer M3 prepared in Examples 1-3 of the present disclosure;

[0034] Fig.10is a stress-strain curve diagram of the elastomer polymer material L1 (polymerized by the comonomer M3) during the recycling of the test example in the present disclosure;

[0035] Fig.11 is a stress-strain curve diagram of the elastic polymer material L1 (polymerized by the comonomer M3) in the test example of the present disclosure during the repetitive stretching;

[0036] Fig.12 is a stress-strain curve diagram of the self-repair of the thermosetting polymer material L3 (polymerized by the comonomer M1) during the stretching in the test example of the present disclosure;

[0037] Fig.13 is a stress-strain curve diagram of the self-repair of the thermosetting polymer material L3 (polymerized by the comonomer M2) during the stretching in the test example of the present disclosure;

[0038] Fig.14 is a stress-strain curve diagram of the self-repair of the thermosetting polymer material L3 (polymerized by the comonomer M3) during the stretching in the test example of the present disclosure;

[0039] Fig.15 3 is a stress-strain curve diagram of the thermoplastic polymer material L2 (polymerized from comonomers M1, M2, and M3, respectively) during stretching in the test examples of the present disclosure. DETAILED DESCRIPTION

[0040] In order to make the objectives, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0041] The endpoints and any values ​​of the ranges disclosed in this disclosure are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in this disclosure.

[0042] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise", "include", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0043] All terms (including technical and scientific terms) used herein have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0044] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the present disclosure shall have the usual meanings understood by persons with ordinary skills in the field to which the present disclosure belongs. If the full text involves descriptions such as "first", "second", etc., the descriptions such as "first", "second", etc. are only used to distinguish similar objects, and cannot be understood as indicating or implying their relative importance, order of precedence, or implicitly indicating the number of technical features indicated. It should be understood that the data described by "first", "second", etc. can be interchangeable under appropriate circumstances.

[0045] Similarly, in order to simplify the present disclosure and help understand one or more of the various disclosed aspects, in the above description of the exemplary embodiments of the present disclosure, the various features of the present disclosure are sometimes grouped together into a single embodiment, figure, or description thereof. The description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" and the like means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present disclosure. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0046] In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by this disclosure.

[0047] In order to overcome the technical problems of the complicated preparation methods and difficulty in finding suitable compounds in the prior art, the present disclosure is committed to developing a series of new polymer material synthesis methods. Specifically, the direct preparation of thermoplastic, thermosetting and elastomeric materials with dynamic exchangeable covalent bonds has become the research focus of the present disclosure. This method can not only give polymer materials more excellent physical and chemical properties, such as higher strength, better toughness and excellent thermal stability, but more importantly, it can also achieve the recyclability and reuse of materials, thereby greatly reducing the burden on the environment.

[0048] In the process of the present disclosure, it was found that olefin ring-opening metathesis polymerization (ROMP) is a very distinctive polymerization method in the preparation of polymer materials. As an efficient and flexible polymerization technology, olefin ring-opening metathesis polymerization has shown unique advantages in the preparation of functionalized polyolefins. The research and development and application of this new synthesis method will not only promote theoretical innovation and technological progress in the field of polymer materials science, but also provide strong scientific and technological support for solving the current global challenges such as resource shortages and environmental pollution. At the same time, it will also inject new vitality and impetus into the transformation and upgrading and sustainable development of related industries, and lead the future polymer materials industry to develop in a more green, environmentally friendly and efficient direction.

[0049] The present disclosure proposes a comonomer for directly preparing a polymer material through olefin metathesis polymerization, wherein the comonomer uses a norbornene group as an end-capping group, and the structure of the comonomer is shown in the following formulas M1 to M3:

[0050] .

[0051] According to an embodiment of the present disclosure, the comonomer uses norbornene as an end-capping group. Norbornene has a unique chemical structure and reactivity, which enables the comonomer to exhibit reactivity during olefin metathesis polymerization. Using the comonomer for olefin metathesis polymerization helps to simplify the polymerization process, improve polymerization efficiency, and reduce the generation of by-products.

[0052] In another aspect of the present disclosure, a method for preparing the aforementioned comonomer is also proposed, comprising:

[0053] Dissolving a compound represented by the following formula A and a compound represented by the following formula B or C in a toluene solvent, and reacting them at a first temperature to obtain a comonomer M1 or a comonomer M2; or,

[0054] Dissolving a compound represented by the following formula D and a compound represented by the following formula E in an N,N-dimethylimidamide solvent, and reacting them at a first temperature to obtain a comonomer M3;

[0055] .

[0056] According to an embodiment of the present disclosure, the molar ratio of compound A to compound B or compound C is 1:2; the molar ratio of compound D to compound E is 1:2; and the first temperature is 70-80°C.

[0057] In another aspect of the present disclosure, a structural monomer of a polymer material directly prepared by olefin metathesis polymerization is also provided. The structural monomer is shown in the following formula (I):

[0058] , formula (I);

[0059] Wherein, X is selected from a borate group or a maleimide group; Y is selected from a C1-C6 alkane, a C1-C6 cycloalkane, a C1-C8 cycloalkene; and m and n are independently selected from integers within the range of 100-1000.

[0060] According to the embodiments of the present disclosure, the polymer material directly prepared by olefin metathesis polymerization proposed in the present disclosure has excellent mechanical, self-healing and recyclable properties due to the abundant dynamic covalent bonds inside its structural monomers, and meets the requirements of green environmental protection.

[0061] According to an embodiment of the present disclosure,

[0062] X is selected from or Group; Y is selected from , or Group.

[0063] According to an embodiment of the present disclosure, the structural monomer is as shown in the following formulas (I-1) to (I-3):

[0064] .

[0065] According to an embodiment of the present disclosure, the polymer material includes a thermoplastic material, a thermosetting material and an elastomeric material.

[0066] In another aspect of the present disclosure, a method for directly preparing a polymer material by olefin metathesis polymerization is also proposed, comprising:

[0067] The aforementioned comonomer is mixed with a cycloolefin monomer, and a metathesis catalyst is added under oil bath conditions to cause a metathesis polymerization reaction to obtain the aforementioned structural monomer; wherein the cycloolefin monomer includes any one of dicyclopentadiene, norbornene and cyclooctene.

[0068] According to the embodiments of the present disclosure, the present disclosure uses a copolymer monomer containing a dynamic covalent bond that can be easily prepared and a dicyclopentadiene (DCPD) or norbornene (NB) or cyclooctene (COE) monomer to undergo an olefin ring-opening metathesis polymerization reaction. Among them, the monomer of the cyclic olefin forms a chain-like high molecular polymer by breaking and recombining the double bonds, while retaining the double bonds in the monomer as dynamic covalent bonds, and obtaining a thermoplastic, thermosetting and elastomeric polymer material in one step. Among them, dicyclopentadiene (DCPD) reacts with the copolymer monomer to obtain a thermosetting polymer material, norbornene (NB) reacts with the copolymer monomer to obtain a thermoplastic polymer material, and cyclooctene (COE) reacts with the copolymer monomer to obtain an elastomeric polymer material.

[0069] According to an embodiment of the present disclosure, the oil bath temperature is 40-45°C.

[0070] According to an embodiment of the present disclosure, the metathesis catalyst is a Grignard catalyst.

[0071] According to the embodiments of the present disclosure, the Grignard catalyst has a highly efficient catalytic activity and can be applied to the ROMP reaction to initiate and accelerate the progress of the ROMP reaction while improving the reaction efficiency and stability.

[0072] It should be noted that the described embodiments are only part of the embodiments of the present disclosure, rather than all of the embodiments. Based on the embodiments of the present disclosure, other embodiments obtained by ordinary technicians in the field without creative work are all within the scope of protection of the present disclosure.

[0073] Example 1-1

[0074] Compound A (2.0 eq.) was dissolved in toluene solvent (concentration: 0.2 M), and compound B (1.0 eq.) was added at room temperature. After reacting for 10 h, the target comonomer M1 was obtained by vacuum distillation. The specific reaction formula is as follows:

[0075] .

[0076] Figure 1 , 2 , 3 are respectively the H NMR spectra of the comonomer M1 prepared in Example 1-1 of the present disclosure 1 HNMR (CDCl3) images, NMR carbon spectra 13 CNMR (CDCl3) and mass spectra.

[0077] like Figure 1-3 As shown, the comonomer M1 was subjected to NMR and mass spectrometry tests to verify its structure and composition.

[0078] Example 1-2

[0079] Compound A (2.0 eq.) was dissolved in toluene solvent (concentration: 0.2 M), and compound C (1.0 eq.) was added at room temperature. After reacting for 10 h, the target comonomer M2 was obtained by vacuum distillation. The specific reaction formula is as follows:

[0080] .

[0081] Figure 4 , 5 , 6 are respectively the H NMR spectra of the comonomer M2 prepared in Examples 1-2 of the present disclosure 1 HNMR (CDCl3) images, NMR carbon spectra 13CNMR (CDCl3) and mass spectra.

[0082] like Figure 4-6 As shown, the comonomer M2 was subjected to NMR and mass spectrometry tests to verify its structure and composition.

[0083] Examples 1-3

[0084] Compound D (2.0 eq.) was dissolved in 100 mL of N,N-dimethylaminoethyl solvent (concentration: 0.2 M), and compound E (1.0 eq.) was added at 70-80 °C. After reacting for 3 h, the target comonomer M3 was obtained by vacuum distillation. The specific reaction formula is as follows:

[0085] .

[0086] Figure 7 , 8 9 are respectively the H NMR spectra of the comonomer M3 prepared in Examples 1-3 of the present disclosure 1 HNMR (CDCl3) images, NMR carbon spectra 13 CNMR (CDCl3) and mass spectra.

[0087] like Figure 7-9 As shown, the comonomer M3 was subjected to NMR and mass spectrometry tests to verify its structure and composition.

[0088] Example 2-1

[0089] In a nitrogen atmosphere, dicyclopentadiene (DCPD) (50 eq.), any one of the comonomers M1, M2, and M3 (1 eq.) prepared in Examples 1-1 to 1-3, and anhydrous dichloromethane (concentration: 0.4 M) were added to a Schlenk reaction flask. The reaction flask was placed in a 40-45 °C oil bath, and Grignard catalyst GII (0.005 eq.) was added to the reaction flask. The reaction was continued for 2 h. After the reaction was completed, the solvent was concentrated, and an appropriate amount of methanol (concentration: 0.3 M) was added to precipitate the polymer. The polymer was filtered, washed, and dried to obtain the elastomeric polymer material L1, and the reaction formula is shown below:

[0090] .

[0091] Example 2-2

[0092] In Example 2-2, a thermoplastic polymer material is prepared. The specific preparation method is the same or similar to that of Example 2-1. The difference from Example 2-1 is that the dicyclopentadiene (DCPD) in Example 2-1 is replaced with norbornene (NB), thereby obtaining a thermoplastic polymer material L2, and the reaction formula thereof is shown below:

[0093] .

[0094] Example 2-3

[0095] In Example 2-3, a thermosetting polymer material is prepared. The specific preparation method is the same or similar to that of Example 2-1. The difference from Example 2-1 is that dicyclopentadiene (DCPD) in Example 2-1 is replaced by cyclooctene (COE), thereby obtaining a thermosetting polymer material L3, and its reaction formula is shown below:

[0096]

[0097] Mechanical properties test

[0098] The mechanical properties of the elastomeric polymer material L1, the thermoplastic polymer material L2 and the thermosetting polymer material L3 prepared in Examples 2-1 to 2-3 were tested: According to the standard test method ASTM638, the specimen was a dumbbell-shaped specimen with a length of 25 mm, a width of 2 mm (at the narrowest point) and a thickness of 0.5 mm. The stress / strain test was carried out at room temperature at a speed of 10 m / min. At least two specimens were tested for each sample.

[0099] Fig.10 It is a stress-strain curve diagram of the elastic polymer material L1 (polymerized by comonomer M3, denoted as L1-M3) during the recycling of stretching in the test example of the present disclosure.

[0100] like Fig.10 As shown in the figure, five curves are shown, representing the elastomer and its strain changes after the first, second, third, and fourth cycles. As the stress increases, the strain of the elastomer after each cycle gradually increases. It can be seen that after multiple cycles of repeated processing, the elastomer polymer materials L1-M3 still maintain good mechanical properties.

[0101] Fig.11 It is a stress-strain curve diagram of the elastomeric polymer material L1 (polymerized by comonomer M3, denoted as L1-M3) in the test example of the present disclosure during the cyclic use of stretching and reciprocating.

[0102] like Fig.11As shown, the strain changes of the elastomeric polymer materials L1-M3 after multiple cycles at different stress levels are shown. In the first cycle, the strain of the elastomer is the largest. This may be because the molecular chain structure inside the elastomer material has undergone major adjustments during the first cycle, resulting in a more significant strain response. As the number of cycles increases, the strain gradually increases, but the growth rate may gradually slow down. This indicates that after multiple cycles, the strain properties of the elastomer may gradually stabilize. However, when the fourth cycle is reached, the strain begins to decrease again. This may be because the elastomeric material has undergone some degree of fatigue or damage after multiple cycles, resulting in a weakened strain response at the same stress level.

[0103] Fig.12 It is a stress-strain curve diagram of the self-repair of the thermosetting polymer material L3 (polymerized by comonomer M1, denoted as L3-M1) during stretching in the test example of the present disclosure.

[0104] like Fig.12 As shown in the figure, due to the dynamic covalent bonds contained in the structural monomer, it has the property of being repairable under heating conditions. At the same time, the sufficient self-repair process makes the thermosetting polymer material L3-M1 have a stronger ability to resist deformation and higher strength and stiffness after self-repair after fracture. The self-repair time has a significant impact on the mechanical properties of the material. The thermosetting polymer material L3-M1 can recover to a higher performance level in a short time.

[0105] Fig.13 , Fig.14 They are stress-strain curves of the thermosetting polymer material L3 (polymerized from comonomers M2, denoted as L3-M2 and M3, denoted as L3-M3) in the test examples of the present disclosure during the tensile self-repair of fracture.

[0106] like Fig.13 , Fig.14 As shown, it is verified that the thermosetting polymer materials L3-M2 and L3-M3 obtained by polymerization of comonomers M2 and M3 also have excellent self-healing properties.

[0107] Fig.15 1 is a stress-strain curve diagram of the thermoplastic polymer material L2 (polymerized from comonomers M1, M2, and M3, respectively, and denoted as L2-M1, L2-M2, and L2-M3, respectively) during stretching in the test examples of the present disclosure.

[0108] like Fig.15 As shown in the figure, with the increase of strain, the stress of the three materials all show an upward trend. This indicates that during the stretching process, the material needs to withstand a greater force to continue to deform. Among them, the L2-M1 material with a larger slope shows a higher stress at the same strain, which means that it has a greater stiffness or higher strength.

[0109] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present disclosure. It should be understood that the above description is only a specific embodiment of the present disclosure and is not intended to limit the present disclosure. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present disclosure should be included in the protection scope of the present disclosure.

Claims

1. A comonomer for directly preparing polymer materials by olefin metathesis polymerization, characterized in that: The comonomer has norbornene as the end-capping group, and the structure of the comonomer is shown in the following formulas M1 to M3: 。 2. A method for preparing the comonomer according to claim 1, comprising: Dissolving the compound represented by the following formula A and the compound represented by the following formula B or C in a toluene solvent, and reacting them under the condition of a first temperature to obtain the comonomer M1 or the comonomer M2; or, Dissolving a compound represented by the following formula D and a compound represented by the following formula E in an N,N-dimethylimidamide solvent, and reacting them at a first temperature to obtain a comonomer M3; 。 3. The method according to claim 2, wherein: The molar ratio of the compound A to the compound B or compound C is 1:2; The molar ratio of the compound D to the compound E is 1:2; The first temperature is 70-80°C.

4. A structural monomer of a polymer material directly prepared by olefin metathesis polymerization, wherein the structural monomer is represented by the following formula (I): , formula (I); in, X is selected from a borate group or a maleamide group; Y is selected from C1-C6 alkanes, C1-C6 cycloalkanes, C1-C8 cycloalkenes; m and n are each independently selected from integers within the range of 100-1000.

5. The structural monomer according to claim 4, wherein: X is selected from or Group; Y is selected from , or Group.

6. The structural monomer according to claim 4, wherein: The structural monomers are shown in the following formulas (I-1) to (I-3): 。 7. The structural monomer according to claim 4, wherein: The polymer material includes thermoplastic material, thermosetting material and elastomeric material.

8. A method for directly preparing a polymer material by olefin metathesis polymerization, comprising: The comonomer according to claim 1 is mixed with a cycloolefin monomer, and a metathesis catalyst is added under oil bath conditions to cause a metathesis polymerization reaction to obtain a structural monomer according to any one of claims 4 to 7; Wherein, the cycloolefin monomer includes any one of dicyclopentadiene, norbornene and cyclooctene.

9. The method according to claim 8, wherein: The oil bath temperature was 40-45°C.

10. The method according to claim 8, wherein: The metathesis catalyst is a Grignard catalyst.

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