CN111320717A - Method for catalyzing vinyl monomer polymerization by using hindered Lewis acid-base pair based on binuclear aluminum Lewis acid - Google Patents

Abstract

The invention discloses a method for catalyzing the polymerization of vinyl monomers by a hindered Lewis acid-base pair based on a dinuclear aluminum Lewis acid, and belongs to the technical field of polymer synthesis. The invention realizes efficient catalysis of vinyl monomers under mild conditions and controllable molecular weight and molecular weight distribution of polymers, and provides a new strategy and method for controllable synthesis of polymers. The polymerization mechanism in the present invention involves the synergistic catalysis of binuclear aluminum for conjugate addition. The dual-core aluminum catalytic system of the invention has the advantages of cheap and easy to obtain, convenient operation, mild reaction conditions, wide adaptability of monomers and the like. In addition, the efficient conversion of different monomers can be achieved by adjusting the pKa of Lewis acid/base, and the molecular weight and molecular weight distribution of the polymer can be precisely regulated, and the initiation efficiency is close to 100%. This type of catalytic system can efficiently catalyze the homopolymerization and copolymerization of methyl methacrylate and butyl acrylate, and also provides a new synthesis strategy and approach for the two copolymer thermoplastic elastomers.

Description

A Hindered Lewis Acid-Base Pair Catalyzed Vinyl Monomer Based on Dinuclear Aluminum Lewis Acids method of bulk polymerization

technical field

The invention relates to a method for catalyzing the polymerization of vinyl monomers based on a hindered Lewis acid-base pair of a dinuclear aluminum Lewis acid, belonging to the technical field of polymer synthesis, in particular to a preparation method of a dinuclear organometallic aluminum Lewis acid and a catalytic vinyl polar mono A living polymerization system for in vivo synthesis of high molecular weight polymers.

Background technique

Polymethyl methacrylate, or PMMA, commonly known as plexiglass, is a transparent organic polymer material. Because of its unique physical and chemical properties, it has the advantages of light texture, easy processing, good light transmittance and resistance, and is widely used in automobile, construction, medicine and other fields. At present, China's demand for PMMA is increasing, but PMMA production technology is mainly mastered by enterprises in developed countries such as the United States and Japan, and China's demand for high-quality PMMA depends on imports. Therefore, in order to get rid of the foreign monopoly of high-end quality PMMA and meet the domestic demand for PMMA, it is necessary to develop technologies to improve the performance of PMMA. At the same time, thermoplastic elastomers based on PMMA are also the best substitutes for styrene elastomers.

The Lewis acid-base pair in the current catalyst for catalyzing the polymerization of polar vinyl monomers can obtain a narrow molecular weight distribution under mild conditions, and the region of non-polar diene can be selectively catalyzed to polymerize, and the obtained polymer The double bond of the monomer can be completely retained. However, most of the existing Lewis acid-base pairs have low initiation efficiency in the polymerization of polar vinyl monomers, complete conversion of monomers cannot be achieved, polymers with high molecular weight and narrow molecular weight distribution cannot be obtained at the same time, and chains are accompanied during the polymerization process. Transfer and chain termination side reactions. In addition, most of the current research is on the mononuclear aluminum Lewis acid system, and there is no report on the catalyst system based on the dinuclear aluminum Lewis acid. Based on the design and synthesis of dinuclear aluminum Lewis acids and the design of Lewis acid-base pairs, the present application provides a new polymerization strategy and method for vinyl polar monomers. At the same time, the di-Lewis acid center can effectively inhibit side reactions, which is a good solution for polar monomers. Homopolymerization and copolymerization experiments provide the possibility, and also provide new strategies and approaches for the synthesis of PMMA-based thermoplastic elastomers under mild conditions.

SUMMARY OF THE INVENTION

The present invention introduces a dinuclear Lewis acid, improves the initiation efficiency of MMA and nBA monomers and suppresses side reactions to achieve efficient and controllable synthesis of PMMA and PnBA, and provides a new strategy and approach for the synthesis of PMMA thermoplastic elastomer under mild conditions. A method for polymerizing other vinyl monomers with hindered Lewis acids and bases based on dinuclear aluminum Lewis acids is also provided.

Technical scheme of the present invention:

A method for catalyzing the polymerization of vinyl monomers by a hindered Lewis acid-base pair based on a dinuclear aluminum Lewis acid. Conjugate addition polymerization reaction is carried out under the catalysis of hindered Lewis acid-base pair composed of Lewis base, the polymerization time is 1s-2h, and the reaction is quenched after the end of the reaction.

Further limited, the structural formula of the dinuclear aluminum Lewis acid is as follows:

In the formula, R ¹ is tert-butyl or 1-methylcyclohexyl, R ² is methyl or tert-butyl, and R ³ is methyl, ethyl or Cl.

Further defined, the Lewis base is an organophosphorus, carbene, carbene or phosphine base.

To be further limited, the structural formula of carbene is:

wherein R is methyl, ethyl, isopropyl, tert-butyl or 2,4,6-trimethylphenyl.

To be further limited, the structural formula of organophosphorus is:

Wherein, R ₁ is methyl, ethyl, phenyl, cyclohexyl, 4-methoxyphenyl, 4-methylphenyl, tert-butyl or n-butyl.

To further define, the structural formula of vinyl polar monomer is:

Wherein, R ₁ is an alkyl group, an aryl group, an alkenyl group, an alkylsilyl group or an alkenylsilyl group, and R ₂ is an alkyl group, an aryl group, an alkenyl group, an alkylsilyl group or an alkenylsilyl group.

Further limited, the organic solvent is one or more of toluene, tetrahydrofuran, hexane, and dichloromethane mixed in any proportion, and the concentration of vinyl monomer in the organic solvent is 1mol/L-10mol/L.

To further define, the molar ratio of vinyl polar monomer, dinuclear aluminum Lewis acid and Lewis base is (200-3200):(1-5):(1-5).

Further limitation: the quencher is a methanol solution containing BHT, and the mass fraction of BHT is 5%-10%.

More specifically, the molar ratio of the quenching agent to the hindered Lewis acid-base pair is 1:1.

The present invention has the following beneficial effects: the present invention utilizes the dinuclear organoaluminum metal complex as the Lewis acid, under the synergistic action of the Lewis base, forms an active species with the polar vinyl monomer, and retains another Lewis acid center, which improves the Catalytic activity and inhibition of kickback phenomenon. During the polymerization process, the active species can not only realize homopolymerization and living polymerization quickly, but also realize block copolymerization between different vinyl polar monomers, especially block copolymerization or random copolymerization between methacrylates. Copolymerization to obtain polymer materials with different properties. The molecular weight of the obtained polymer is proportional to the molar ratio (monomer to catalyst). By adjusting the molar ratio of monomer to catalyst, polymers of different molecular weights can be obtained, and even ultra-high molecular weight polymers can be obtained with a molecular weight of 2×10 ⁶ Above g/mol level, the measured molecular weight of the obtained polymer is consistent with the theoretical value, and the molecular weight distribution is narrow.

To sum up, the beneficial technical effects obtained by the present invention are summarized as follows:

(1) The raw materials of the dual-nuclear catalytic system of the present invention are cheap and free of precious metals.

(2) The design of the present invention takes aluminum as the center of the dinuclear Lewis acid, and forms a large sterically hindered Lewis acid with the ligand, which improves the

Catalytic activity, when the polymerization is accelerated, the complete conversion of the monomer can be completed within 2 minutes (the friction between the monomer and the catalyst).

Albi can reach 3200:1).

(3) The catalytic system of the present invention can precisely regulate the molecular weight of the polymer, and the molecular weight distribution is narrow (<1.2),

The initiation efficiency is close to 100%, and the actual molecular weight is close to the theoretical molecular weight.

(4) the catalytic system of the present invention can not only realize methyl methacrylate, butyl acrylate and other polar vinyl

The active controllable polymerization of monomers, and can also realize the block copolymerization of methyl methacrylate, butyl acrylate and

Homopolymerization and copolymerization of other polar vinyl monomers.

Detailed ways

The experimental methods used in the following examples are conventional methods unless otherwise specified. The used materials, reagents, methods and instruments, unless otherwise specified, are conventional materials, reagents, methods and instruments in the art, which can be obtained by those skilled in the art through commercial channels.

The structure and numbering of the dinuclear aluminum Lewis acid used in the following examples are as follows:

其中，R¹为叔丁基，R²为甲基，R³为甲基。[Al(mbmp)Me] ₂ is

Wherein, R ¹ is tert-butyl, R ² is methyl, and R ³ is methyl.

The structures and numbers of Lewis bases are as follows:

^MesI_m：

^iPrI_m：

^tBuIm _:

^{Mes Im} _:

^iPrIm _:

Wherein, R ₁ is cyclohexyl, ethyl, phenyl, 4-methoxyphenyl or 4-methylphenyl.

Example 1

In the glove box, add the specified amount of Lewis acid ([Al(mbmp)Me] ₂ ) and the specified amount of MMA to the Schlenk bottle, then add 2 mL of the toluene solution, stir well, and then add the specified amount of Lewis to the bottle The base ( ^iPrIm ) was _added , and the reaction started timing. After the reaction, the Schlenk bottle was taken out from the glove box, and the methanol solution containing 5% BHT was added to quench it. The remaining liquid was extracted with a large amount of methanol, the solid was taken out, dried in a vacuum drying oven at 40°C to constant weight, the conversion rate was calculated according to the NMR results, and the molecular weight and molecular weight distribution of the obtained polymer were measured by gel permeation chromatography. The reaction conditions and test results are as follows:

The polymerization results obtained under different reaction conditions with alkali ( ^iPrIm ) as _Lewis base in table 1 are as follows

By designing the ratio of different monomers and catalysts, observing the linear increase of the conversion rate with time and the linear increase of molecular weight with the conversion rate, while the molecular weight distribution PDI keeps a narrow distribution, it can effectively prove that the reaction is a controllable living polymerization. Example 2

The reaction was carried out in a glove box, and 0.024 mmol of Lewis acid ([Al(mbmp)Me] ₂ ), 2 mL of toluene and 0.5 mL (4.8 mmol) of MMA were sequentially added to the Schlenk flask, and 0.024 mmol of Lewis acid was added after stirring evenly. Alkali, after the addition of materials, the reaction starts timing. After the reaction is completed, take the schlenk bottle out of the glove box, add methanol solution containing 5% BHT to quench, take 0.2 mL of it in 0.4 mL of deuterated chloroform to measure its NMR, and then put the remaining The liquid was extracted with a large amount of methanol, the solid was taken out, dried in a vacuum drying oven at 40°C to constant weight, the conversion rate was calculated according to the NMR results, and the molecular weight and molecular weight distribution of the obtained polymer were measured by gel permeation chromatography. The reaction conditions and test results are as follows:

Table 2 Synergistic catalysis of MMA polymerization by [Al(mbmp)Me] ₂ and different Lewis bases

Through this set of experiments, it is proved that the initiation efficiency of the MMA monomer based on the dinuclear aluminum Lewis acid and the Lewis base used is 100%. The superiority of the dinuclear aluminum Lewis acid can be drawn.

Example 3

The reaction was carried out in a glove box, and the specified Lewis acid ([Al( _mbmp )Me] ₂ ), 2 mL of solvent and quantitative MMA were successively added to the Schlenk bottle, and the Lewis base ( ^iPrIm ) was added after stirring, and the addition was completed, The timing of the reaction starts. After the reaction is over, take the schlenk bottle out of the glove box, add methanol solution containing 5% BHT to quench it, take 0.2 mL of it in 0.4 mL of deuterated chloroform to measure its NMR, and then add a large amount of methanol to the remaining liquid. Extract the solid, take out the solid, and dry it in a vacuum drying oven at 40°C to constant weight, calculate the conversion rate according to the NMR results, and measure the molecular weight and molecular weight distribution of the obtained polymer by gel permeation chromatography. The reaction conditions and test results are as follows:

Table 3 Polymerization of MMA in different solvents

Through the above experiments with different solvents, it can be concluded that the dinuclear Lewis acid-base pair can exhibit excellent catalytic activity in different reagents.

Example 4

The reaction was carried out in a glove box, and 0.024 mmol of Lewis acid ([Al(mbmp)Me] ₂ ), 2 mL of dichloromethane and 0.68 mL (4.8 mmol) of nBA were sequentially added to the Schlenk flask, and 0.024 mmol was added after stirring evenly. After the reaction was completed, the Schlenk bottle was taken out from the glove box, quenched by adding methanol solution containing 5% BHT, and 0.2 mL was taken in 0.4 mL deuterated chloroform to measure its NMR, and then The remaining liquid was extracted with a large amount of methanol, the solid was taken out, dried in a vacuum drying oven at 40°C to constant weight, the conversion rate was calculated according to the NMR results, and the molecular weight and molecular weight distribution of the obtained polymer were measured by gel permeation chromatography. The reaction conditions and test results are as follows:

Table 4 [Al(mbmp)Me] ₂ and different Lewis bases synergistically catalyze nBA polymerization

Through this set of experiments, it is proved that the Lewis acid-base pair composed of the dinuclear aluminum Lewis acid and organophosphorus has excellent catalytic activity for nBA monomer, and the molecular weight distribution is controllable.

Example 5

In the glove box, add the specified amount of Lewis acid ([Al(mbmp)Me] ₂ ), the specified amount of nBA to the Schlenk bottle, then add 2 mL of the toluene solution, stir well, and then add the specified amount to the bottle Lewis base ( ^{Mes Im} ₎ . After the addition of materials, the reaction starts to time. After the reaction, the Schlenk bottle was taken out of the glove box, quenched by adding methanol solution containing 5% BHT, and 0.2 mL was taken in 0.4 mL deuterochloroform to measure its NMR, and then the remaining liquid was quenched. Extract it with a large amount of methanol, take out the solid, dry it in a vacuum drying oven at 40°C to constant weight, calculate the conversion rate according to the NMR results, and measure the molecular weight and molecular weight distribution of the obtained polymer by gel permeation chromatography. The reaction conditions and test results are as follows:

The polymerization result that table 5 _obtains under different reaction conditions with alkali ( ^MesIm ) as Lewis base is as follows

Through this set of experiments, it is proved that the Lewis acid-base pair composed of the dinuclear aluminum Lewis acid and carbene ^Mes _Im has excellent catalytic activity for nBA monomers, and the molecular weight distribution is controllable. At the same time, with the linear increase of the monomer amount, the polymer The molecular weight also increased linearly, demonstrating controlled polymerization.

Example 6

The reaction was carried out in a glove box, and the specified Lewis acid ([Al( _mbmp )Me] ₂ ), 2 mL of solvent and quantitative nBA were successively added to the Schlenk bottle, and the Lewis base ( ^iPrIm ) was added after stirring, and the addition was completed, The timing of the reaction started. After the reaction was over, the Schlenk bottle was taken out of the glove box, quenched by adding methanol solution containing 5% BHT, taking 0.2 mL in 0.4 mL deuterochloroform to measure its NMR, and then adding a large amount of methanol to the remaining liquid. Extract the solid, take out the solid, and dry it in a vacuum drying oven at 40°C to constant weight, calculate the conversion rate according to the NMR results, and measure the molecular weight and molecular weight distribution of the obtained polymer by gel permeation chromatography. The reaction conditions and test results are as follows:

Table 6 Polymerization of nBA in different solvents

Through this set of experiments, it is proved that the Lewis acid-base pair composed of the _dinuclear aluminum Lewis acid and carbene ^iPrIm has excellent catalytic activity for nBA monomer in different solvents, and the molecular weight distribution is controllable. Linearly increased, the polymer molecular weight also increased linearly, demonstrating controlled polymerization.

Example 7

In the glove box, add a certain amount of Lewis acid ([Al(mbmp)Me] ₂ ) to the Schlenk bottle, then add 5 mL of toluene solvent to fully dissolve it, and then add 1.5 mL (mmol) of MMA to it, The Lewis base ( ^iPrIm ) of the specified amount was added after it was fully _reacted , and the feeding was completed, and the reaction started timing. After the monomer was completely transformed, 0.2 mL was taken in a 5mL glass bottle for subsequent use, and then the same amount of MMA was added, repeated three times. After the reaction, the Schlenk bottle was taken out of the glove box, quenched by adding methanol solution containing 5% BHT, and 0.2 mL was taken into a 5 mL glass bottle for later use, and then the remaining liquid was extracted with a large amount of methanol, and the solid was taken out. It was dried in a vacuum drying oven at 40°C to constant weight, and the molecular weight and molecular weight distribution of the obtained polymer were measured by gel permeation chromatography. The reaction conditions and test results are as follows:

Table 7 Experimental results of chain growth of MMA polymerization

Through the above chain addition experiments, it is proved that the above system is a living polymerization for MMA.

Example 8

In the glove box, add a certain amount of Lewis acid ([Al(mbmp)Me] ₂ ) to the Schlenk bottle, then add 5 mL of dichloromethane solvent to make it fully dissolved, and then add 0.8 mL (mmol) of nBA, add the Lewis base ( ^iPrIm ) of the specified amount after it is fully reacted, the addition is completed, the reaction starts timing, after the monomer is completely converted, _0.2mL is taken in a 5mL glass bottle for subsequent use, and then the same amount of nBA is added, so Repeat three times. After the reaction, take the schlenk bottle out of the glove box, add methanol solution containing 5% BHT to quench, take 0.2 mL in a 5 mL glass bottle for later use, and then extract the remaining liquid with a large amount of methanol, take out the solid , dried at 40°C in a vacuum drying oven to constant weight, and the molecular weight and molecular weight distribution of the obtained polymer were measured by gel permeation chromatography. The reaction conditions and test results are as follows:

Table 8 Experimental results of chain growth of nBA polymerization

Through the above chain addition experiments, it is proved that the above system is a living polymerization for nBA.

Claims (10)

1. A method for catalyzing vinyl monomer polymerization by a hindered Lewis acid-base pair based on binuclear aluminum Lewis acid is characterized in that vinyl polar monomers are used as raw materials in an organic solvent at room temperature, conjugate addition polymerization reaction is carried out under the catalysis of the hindered Lewis acid-base pair consisting of binuclear aluminum Lewis acid and Lewis base, the polymerization time is 1s-2h, and methanol is used for quenching after the reaction is finished.

2. The method of claim 1, wherein said binuclear aluminum Lewis acid has the following structural formula:

in the formula, R¹Is tert-butyl or 1-methylcyclohexyl, R²Is methyl or tert-butyl, R³Is methyl, ethyl or Cl.

3. The method of claim 1, wherein the Lewis base is an organophosphorus, carbene or phosphine base.

4. The method of claim 3, wherein the carbene has the following structural formula:

wherein R is methyl, ethyl, isopropyl, tert-butyl or 2,4, 6-trimethylphenyl.

5. The method of claim 3, wherein the organophosphorus ligand has a formula of:

wherein R is₁Is methyl, ethyl, phenyl, cyclohexyl, 4-methoxyphenyl, 4-methylphenyl, tert-butyl or n-butyl.

6. The method of claim 1, wherein the vinyl polar monomer has a formula of:

wherein R is₁Is alkyl, aryl, alkenyl, alkylsilyl or alkenylsilyl, R₂Is alkyl, aryl, alkenyl, alkylsilyl or alkenylsilyl.

7. The method according to claim 1, wherein the organic solvent is one or more of toluene, tetrahydrofuran, hexane and dichloromethane, and the concentration of the vinyl monomer in the organic solvent is 1mol/L-10 mol/L.

8. The method of claim 1, wherein the molar ratio of the vinyl polar monomer, the dialuminum Lewis acid and the Lewis base is (200-3200): (1-5): 1-5).

9. The method for catalyzing vinyl monomer polymerization by using hindered lewis acid-base pair based on binuclear aluminum lewis acid as claimed in claim 1, wherein the quenching agent is a methanol solution containing BHT with a mass fraction of 5% -10%.

10. The method for catalyzing vinyl monomer polymerization by using hindered lewis acid-base pair based on binuclear aluminum lewis acid according to claim 1 or 9, wherein the molar ratio of the amount of the quencher used to the hindered lewis acid-base pair is 1: 1.