RU2768465C1 - Method of producing additive polymers based on norbornene (embodiments) - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: present invention relates to two embodiments of a method of producing polymers based on compounds of the norbornene series. According to one embodiment, a method of producing an additive polymer of a norbornene-based compound by mixing a norbornene-based compound with an organic solvent, adding a pre-catalyst containing a palladium compound Pd(0) or Pd(2+), and an organic cocatalyst, carrying out an additive polymerisation reaction and extracting the obtained polymer is characterized by that said monomer used is norbornene, cocatalyst is n-nitroiodobenzene or arendiazonium salt in molar ratio norbornene / palladium in range of 100/1–1000/1.

EFFECT: use of available organic compounds for activation of the pre-catalyst and sharp reduction in consumption of the cocatalyst, which enables to obtain additive polymers of norbornene and its derivatives with high molecular weight (degree of polymerisation).

4 cl, 7 ex, 1 dwg

Description

The invention relates to a new method for producing additive polymers of compounds based on norbornene and can be used in various fields of industry, due to their unique properties - high thermal stability, transparency, the possibility of synthesizing polymers with high glass transition temperatures, good mechanical properties, etc.

Norbornene and its derivatives can enter into polymerization by various mechanisms to form polymers with different backbone structures. Ring-opening metathesis polymerization leads to the formation of flexible-chain polymers containing double bonds in the main chain. Additive polymerization of norbornene derivatives makes it possible to obtain polymers with a saturated rigid main chain consisting of repeating norbornene units. This leads to the fact that materials based on additive polynorbornenes have a number of attractive performance characteristics: high thermal and chemical stability, high glass transition temperature, interesting gas transport and dielectric characteristics [Karpov, G.O., Alentiev, DA, Wozniak, AI, Bermesheva, E.V., Lounev, IV, Gusev, YA, Shantarovich, V.P., & Bermeshev, M.V. (2020). Dielectric properties of addition and metathesis polynorbornenes with bulky side-substituents. Polymer, 203(April), 122759. https://doi.Org/10.1016/j.polymer.2020.122759; Bermeshev, M.V., & Chapala, P.P. (2018). Addition polymerization of functionalized norbornenes as a powerful tool for assembling molecular moieties of new polymers with versatile properties. Progress in Polymer Science, 84, 1-46. https://doi.org/10.1016/j.progpolymsci.2018.06.003]. To obtain polynorbornene according to the additive scheme, transition metal compounds (Ni, Co, Pd, Ti, Cr, Fe) are used, and organometallic compounds of boron and aluminum are used as activators.

The disadvantages of this approach are the instability of organometallic activators to the action of oxygen and air moisture, which requires the process to be carried out in an inert atmosphere, as well as the high cost of organometallic reagents.

In addition, the use of organometallic compounds for the activation of transition metal compounds leads to an increase in the residual content of metals in the resulting polymers, which adversely affects the performance of materials based on them.

Pd compounds have previously demonstrated high activity in the addition polymerization of norbornenes and tolerance to the functional groups contained in the structure of these monomers. Studies of catalytic systems based on Pd compounds have shown that the key step in the activation process is the formation of a Pd-C bond [Bermesheva, E.V., Wozniak, AI, Andreyanov, FA, Karpov, GO, Nechaev, MS, Asachenko, AF, Topchiy, MA, Melnikova, EK, Nelyubina, YV, Gribanov, PS, & Bermeshev, MV (2020). Polymerization of 5-alkylidene-2-norbornenes with highly active pd-n-heterocyclic carbene complex catalysts: catalyst structure-activity relationships. ACS Catalysis, 10(3), 1663-1678. https://doi.org/10.1021/acscatal.9b04686].

The disadvantage of this method is that it uses expensive co-catalysts and palladium catalysts. In addition, the combination of catalyst and co-catalyst used in the known method is only effective for the polymerization of 5-vinyl-2-norbornene, 5-ethylidene-2-norbornene and dicyclopentadiene.

The formation of the Pd-C bond is realized not only in the presence of organometallic reagents, but also when Pd(0) and Pd(2 ⁺ ) compounds are exposed to various organic compounds - alkyl- and aryl halides, arenediazonium salts, carboxylic acid chlorides, etc.

It was previously shown that the formation of the Pd-C fragment required for addition polymerization occurs during the Catellani reaction at the stage of oxidative addition of Pd(0) complexes to aryl halides [Delia Ca, N., Fontana, M., Motti, E., & Catellani, M. (2016). Pd/Norbomene: A Winning Combination for Selective Aromatic Functionalization via C-H Bond Activation. Accounts of Chemical Research, 49(7), 1389-1400. https://doi.org/10.1021/acs.accounts.6b00165].

The initial stages of the Catellani reaction in the presence of iodobenzene (L-ligand) are shown in Scheme 1.

Moreover, it has been demonstrated that norbornene is able to insert into the formed Pd-C bond, which makes this approach attractive from the point of view of macromolecular chemistry [Chai, D.I., Thansandote, P., & Lautens, M. (2011). Mechanistic studies of Pd-catalyzed regioselective aryl C-H bond functionalization with strained alkenes: Origin of regioselectivity. Chemistry - A European Journal, 17(29), 8175-8188. https://doi.org/10.1002/chem.201100210]. Therefore, available organic compounds can be considered effective cocatalysts for the addition polymerization of norbornene in the presence of Pd(0) and Pd(2+) compounds.

The disadvantage of the described method lies in the possibility of introducing only one molecule of norbornene into the Pd-C bond, while polymerization with the formation of a polymer based on norbornene is not achieved.

As a rule, the catalytic systems used for the addition polymerization of norbornene derivatives are two- or three-component, consisting of a transition metal salt (for example, Pd(0) or Pd(2+) complexes), a cocatalyst (a compound that activates the transition metal salt by forming metal-carbon bonds) and, in some cases, phosphine (introduced into the system to stabilize the active catalytic species, if necessary). Organoelement cocatalysts are often used to activate Pd(0) and Pd(2+) compounds. For example, such as methylalumoxane (MAO), organoboron compounds (B(C ₆ F ₅ ) ₃ , Na ⁺ [B(3,5-(CF ₃ ) ₂ C ₆ H ₃ ) ₄ ] ^- etc.).

These compounds are effective cocatalysts, but have two significant disadvantages:

- they are less accessible from an economic point of view, because are expensive;

- are sensitive to oxygen and/or water, which is associated with the loss of activity of the entire catalytic system.

For example, in [D. Yang, Y. Tang, H. Song, B. Wang, Synthesis, Structures, and Norbornene Polymerization Behavior of Palladium Complexes Bearing Tridentate o-Aryloxide-N-heterocyclic Carbene Ligands, Organometallics 35(10) (2016) 1392-1398. doi:10.1021/acs.organomet.5b01006] to activate a palladium complex bearing an N-heterocyclic carbene ligand, a MAO cocatalyst was used to carry out the addition polymerization of norbornene.

The closest in technical essence and the achieved result is a method for obtaining additive polymers of compounds based on norbornene, described in [E.V. Bermesheva, A.I. Wozniak, F.A. Andreyanov, G.O. Karpov, M.S. Nechaev, A.F. Asachenko, M.A. Topchiy, E.K. Melnikova, Y.V. Nelyubina, P.S. Gribanov, M.V. Bermeshev, Polymerization of 5-Alkylidene-2-norbornenes with Highly Active Pd-N-Heterocyclic Carbene Complex Catalysts: Catalyst Structure-Activity Relationships, ACS Catalysis 10(3) (2019) 1663-1678. doi:10.1021/acscatal.9b04686] this work is not suitable as a prototype, there are no our monomers, other monomers. For the prototype it is better to take [D. Yang, Y. Tang, H. Song, B. Wang, Synthesis, Structures, and Norbornene Polymerization Behavior of Palladium Complexes Bearing Tridentate o-Aryloxide-N-heterocyclic Carbene Ligands, Organometallics 35(10) (2016) 1392-1398. doi:10.1021/acs.organomet.5b01006]. The method of polymerization of norbornene is carried out in the presence of palladium Pd(2+) complexes containing an N-heterocyclic carbene ligand, as one of the most active in the polymerization of norbornene and cocatalyst -methylalumoxane (MAO).

However, a significant disadvantage of the known method is the fact that the polymerization of norbornene proceeds only when using low molar ratios of monomer/cocatalyst ((2-5)/1) and Pd/cocatalyst (1/(2250-5000)). In other words, to activate the palladium complex, it is necessary to use a large excess of the cocatalyst (up to 5000 times more) and, in fact, polymerization proceeds under oligomerization conditions, when the molar ratio of one of the components of the catalytic system and the monomer, norbornene, is low, in this case ((2- 5)/1). Another disadvantage of the method according to the prototype is the need to provide an inert atmosphere - the catalyst and co-catalyst are not stable in air, in the presence of moisture.

The objective of the present invention is to develop a method for the addition polymerization of norbornene and its derivatives, in which the activation of the Pd(0) and Pd(2+) compounds was carried out by available organic cocatalysts while reducing their consumption and the possibility of carrying out the reaction in air, with the production of addition polymers of norbornene and its derivatives with a weight average molecular weight of more than 5.7×10 ³ .

The problem in the first embodiment of the invention is solved by the fact that in the method of obtaining an additive polymer of the norbornene-based compound by mixing the monomer of the norbornene-based compound with an organic solvent, adding a precatalyst containing a palladium compound Pd(0) or Pd(2+) and an organic cocatalyst , carrying out the addition polymerization reaction and isolating the resulting polymer, norbornene is used as the indicated monomer, p-nitroiodobenzene or arenediazonium salt is used as a cocatalyst at a norbornene/palladium molar ratio in the range of 100/1-1000/1, and the addition polymerization reaction is carried out in air .

As the palladium compound, in particular, palladium acetate is used. Other palladium compounds can also be used, for example, bis(dibenzylideneacetone) palladium - (Pd(dba) ₂ ).

When an arenediazonium salt is used as the cocatalyst, the addition polymerization reaction is carried out in air.

The objective of the second embodiment of the invention is solved by the fact that in a method for producing an addition polymer of a norbornene-based compound by mixing a norbornene-based compound monomer with an organic solvent, adding a precatalyst containing a Pd(0) palladium compound and an organic cocatalyst, carrying out an addition polymerization reaction, and isolation of the resulting polymer, poly(5-n-hexyl-2-norbornene) or poly(5-n-decyl-2-norbornene) is used as a monomer, bis(dibenzylideneacetone) palladium (0) as a palladium compound, as a cocatalyst - salt arenediazonium at a molar ratio of monomer/palladium 250/1, and the addition polymerization reaction is carried out in air.

The technical result of using the proposed technical solution is the use of available organic compounds to activate the precatalyst and a sharp decrease in the consumption of the cocatalyst (the molar ratios of Pd/cocatalyst can be from 1/1 to 1/5, and the consumption of the cocatalyst is reduced by orders of magnitude), which provides additive polymers of norbornene and its derivatives with a high molecular weight (degree of polymerization).

In addition, the organic cocatalysts used make it possible to carry out the addition polymerization of norbornene and its derivatives in air and in the presence of traces of water.

The following examples illustrate the invention.

Materials, preparation of reagents and solvents

The precatalysts, cocatalysts, norbornene, 5-n-hexyl-2-norbornene, 5-n-decyl-2-norbornene, and solvents used in the work were purchased from Sigma Aldrich and used without preliminary purification. All operations for the synthesis of polymers are carried out in an inert atmosphere in a glove box, unless otherwise indicated.

Research methods

NMR spectra were recorded on a Bruker Avance DRX 400 NMR spectrometer at registration frequencies of 400.1 MHz ( ¹ H NMR) and 100.6 MHz ( ¹³ C NMR) in CDCl ₃ solution. The signals in the spectra]H are assigned to the residual protons of CDCl ₃ (7.24 ppm).

Analysis of the molecular weights of the polymers was carried out by gel permeation chromatography (GPC) on a Waters system with a differential refractometer (Chromatopack Microgel-5; eluent chloroform; flow rate 1 ml/min). Molecular weights are calculated according to the standard method relative to standard samples of monodisperse polystyrene.

Example 1

6.1 mg of Pd(0)-bis(dibenzylideneacetone) palladium (0) complex (Pd(dba) ₂ , 1×10 ^-2 mmol, 1 molar equivalent), 12.5 mg of n-nitroiodobenzene (5× 10 ^-2 mmol, 5 molar equivalents) and 0.15 ml of absolute toluene.

The ratio of norbornene/palladium is 100/1 and palladium/cocatalyst is 1/5.

The mixture is stirred for 5 minutes. With stirring, 0.157 ml of a solution of norbornene in toluene (1.1 mmol, 100 mole equivalents) is added. The reaction is carried out with stirring at a temperature of 25°C for 2 hours.

Polynorbornene in its pure form is isolated as follows. The reaction mass is poured into methanol (15 ml). The precipitate formed is filtered off and washed with two portions of methanol (5 ml). The precipitate is then dried under reduced pressure for 6 hours. The product is precipitated twice from toluene into methanol and dried to constant weight.

Get polynorbornene structural formula:

characterized by the following molecular weight

distribution: M _w =5.7×10 ³ and M _n =3.4×10 ³

The yield of polynorbornene is 75%.

Example 2

Differs from example 1 using 7.5 mg of n-nitroiodobenzene as co-catalyst (3×10 ^-2 mmol, 3 molar equivalents).

The ratio of norbornene/palladium is 100/1 and palladium/cocatalyst is 1/3.

Get polynorbornene structural formula:

characterized by the following molecular weight distribution: M _w =5.9×10 ³ and M _n =3.5×10 ³

The yield of polynorbornene is 68%.

Example 3

0.307 ml of a solution of norbornene in toluene (2.1 mmol, 1000 mol equivalents) and 0.355 ml of absolute chloroform are placed in a 4 ml glass vial. Then 0.4 ml of 0.0053 M catalytic mixture of Pd(0) - bis(dibenzylideneacetone)palladium (0) complex (Pd(dba) ₂ , 2.1×10 ^-3 mmol, 1 molar equivalent) with p-nitrobenzenediazonium tetrafluoroborate (6.3× 10 ^-3 mmol, 3 molar equivalents). The reaction is carried out with stirring at a temperature of 25°C for 15 minutes in air.

The ratio of norbornene/palladium is 1000/1 and palladium/cocatalyst is 1/3.

The resulting polynorbornene in its pure form is isolated as follows. The reaction mass is poured into methanol (20 ml). The precipitate formed is filtered off and washed with two portions of methanol (5 ml). The precipitate is then dried under reduced pressure for 6 hours. The product is twice reprecipitated from chloroform into methanol and dried to constant weight.

Get polynorbornene structural formula:

characterized by molecular weight distribution: M _w =55×10 ³ and M _n =42×10 ³ and solubility in chloroform and toluene.

The yield of polynorbornene is 72%.

Example 4

Differs from example 3 using a catalyst mixture based on Pd(dba) ₂ and tetrafluoroborate n-(trifluoromethyl)benzenediazonium as co-catalyst (6.3×10 ^-3 mmol, 3 molar equivalents).

The ratio of norbornene/palladium is 1000/1 and palladium/cocatalyst is 1/3.

Get polynorbornene structural formula:

characterized by molecular weight distribution: M _w =59×10 ³ and M _p =37×1 ³ and solubility in chloroform and toluene.

The yield of polynorbornene is 76%.

Example 5

Into a 4 ml glass vial are placed 2.4 mg of palladium acetate (1×10 ^-2 mmol, 1 mole equivalent), 8 mg of p-nitroiodobenzene (3×10 ^-2 mmol, 3 mole equivalents) and 0.17 ml of absolute toluene. The mixture is stirred for 5 minutes. With stirring, 0.157 ml of a solution of norbornene in toluene (1.1 mmol, 100 mole equivalents) is added. The reaction is carried out with stirring at a temperature of 25°C for 18 hours.

A norbornene/palladium ratio of 100/1 and a palladium/cocatalyst ratio of 3/1 are used.

Polynorbornene in its pure form is isolated as follows. The reaction mass is poured into methanol (15 ml). The precipitate formed is filtered off and washed with two portions of methanol (5 ml). The precipitate is then dried under reduced pressure for 6 hours. The product is precipitated twice from toluene into methanol and dried to constant weight.

Get polynorbornene structural formula:

characterized by molecular weight distribution: M _w =4.8×10 ³ and M _n =2.5×10 ³ and solubility in chloroform and toluene.

The yield of polynorbornene is 87%.

Example 6

0.2 g of 5-n-hexyl-2-norbornene (1.2 mmol, 250 mol equivalents) and 0.481 ml of absolute chloroform are placed in a 4 ml glass vial. Then, 0.5 ml of 0.0094 M catalytic mixture of Pd(dba) ₂ (4.8×10 ^-3 mmol, 1 mole equivalent) with p-nitrobenzenediazonium tetrafluoroborate (1.4×10 ^-2 mmol, 3 mole equivalents) is added with stirring. The reaction is carried out with stirring at a temperature of 25°C for 30 minutes in air.

The ratio of norbornene/palladium is 250/1 and palladium/cocatalyst is 1/3.

Additive poly(5-n-hexylnorbornene) in pure form is isolated as follows. The reaction mass is poured into methanol (20 ml). The precipitate formed is filtered off and washed with two portions of methanol (5 ml). The precipitate is then dried under reduced pressure for 6 hours. The product is twice reprecipitated from chloroform into methanol and dried to constant weight.

Get additive poly(5-n-hexylnorbornene) structural formula:

characterized by M _w =42×10 ³ and M _n =20×10 ³ and solubility in chloroform.

The yield of additive poly(5-n-hexylnorbornene) is 95%.

¹ H NMR spectrum. The spectrum contains broadened proton signals of the norbornane and hexyl fragments in the region of 0.4–2.7 ppm. with a total integral of 22H, which indicates the formation of a polymer. In the spectrum, there are no signals from the protons of the norbornene double bond (range 6.0-6.2 ppm), which indicates that the resulting polymer has a saturated main chain.

Example 7

0.2 g of 5-n-decyl-2-norbornene (8.6×10 ^-1 mmol, 250 molar equivalents) and 0.479 ml of absolute chloroform are placed in a 4 ml glass vial. Then, with stirring, 0.5 ml of 0.0068 M Pd(dba) ₂ catalytic mixture (3.4×10 ^-3 mol, 1 mole equivalent) with p-nitrobenzenediazonium tetrafluoroborate (1×10 ^-2 mol, 3 mole equivalents) is added. The reaction is carried out with stirring at a temperature 25°C for 30 minutes.

The ratio of norbornene/palladium is 250/1 and palladium/cocatalyst is 1/3.

Additive poly(5-n-decylnorbornene) in its pure form is isolated as follows. The reaction mass is poured into methanol (20 ml). The precipitate formed is filtered off and washed with two portions of methanol (5 ml). The precipitate is then dried under reduced pressure for 6 hours. The product is twice reprecipitated from chloroform into methanol and dried to constant weight.

Get additive poly(5-n-decylnorbornene) structural formula:

characterized by M _w =44×10 ³ and M _n =20×10 ³ and solubility in chloroform.

The yield of additive poly(5-n-decyl norbornene) is 80%.

¹ H NMR spectrum. The spectrum contains broadened proton signals of the norbornane and decyl fragments in the region of 0.45–2.55 ppm. with a total integral of 30H, which indicates the formation of a polymer. In the spectrum, there are no signals from the protons of the norbornene double bond (range 6.0-6.2 ppm), which indicates that the resulting polymer has a saturated main chain.

The process is based on the use of available organic reagents as activators and can proceed not only in an inert atmosphere, but also in air.

Varying the concentration of the monomer in the reaction mixture makes it possible to determine the optimal conditions for polymerization in terms of yields and molecular weight characteristics of the polymers.

In FIG. 1 shows the dependence of polynorbornene yields on the monomer concentration in the reaction mixture in the presence of the catalytic system - Pd(dba) ₂ /4-NO ₂ C ₆ H ₄ N ₂ ⁺ BF ₄ ^- ; molar ratio norbornene/Pd=1000/1; molar ratio Pd(dba) ₂ /NO ₂ PhN ₂ ⁺ BF ₄ ^- =1/3; the solvent is chloroform; reaction time - 15 minutes, temperature - 25°C; on air. Polymerizations are performed analogously to example 3, but at different concentrations of norbornene in the mixture. The nature of the dependence indicates that the presented catalytic systems have a noticeable activity in a fairly wide range of concentrations. In this case, an increase in the concentration of norbornene above 2 M does not lead to a significant change in the yields of the polymer.

The type of catalytic systems described in this application makes it possible to involve in additive polymerization not only unsubstituted norbornene, but also its derivatives - 5-n-hexyl-2-norbornene or 5-n-decyl-2-norbornene (examples 6 and 7).

Claims (4)

1. A method for producing an addition polymer of a norbornene-based compound by mixing a norbornene-based compound with an organic solvent, adding a precatalyst containing a Pd(0) or Pd(2+) palladium compound and an organic co-catalyst, carrying out an addition polymerization reaction, and isolating the resulting polymer, characterized in that norbornene is used as said monomer, n-nitroiodobenzene or arenediazonium salt is used as cocatalyst at norbornene/palladium molar ratio within 100/1-1000/1. 2. The method according to p. 1, characterized in that palladium acetate is used as the palladium compound. 3. The method according to claim 1, characterized in that when an arenediazonium salt is used as the co-catalyst, the addition polymerization reaction is carried out in air. 4. A method for producing an addition polymer of a norbornene-based compound by mixing a norbornene-based compound monomer with an organic solvent, adding a precatalyst containing a Pd(0) palladium compound and an organic cocatalyst, carrying out an addition polymerization reaction, and isolating the resulting polymer, characterized in that as poly(5-n-hexyl-2-norbornene) or poly(5-n-decyl-2-norbornene) is used as a monomer; the molar ratio monomer/palladium is 250/1, and the addition polymerization reaction is carried out in air.

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