CN111303325B - Efficient controllable preparation method of polyisoprene - Google Patents

Abstract

An efficient and controllable method for preparing polyisoprene. The invention belongs to the field of conjugated diene catalytic polymerization. The present invention solves the technical problems of low activity, uncontrollable selectivity and sensitive and easy deactivation of the existing iron-based catalyst. The method of the present invention is as follows: under an inert gas atmosphere, the isoprene monomer, the rigid framework iron complex, the co-catalyst and the solvent are added to the reactor, and the reaction is stirred at ‑40 to 100 ° C for 12s to 120min, and the reaction is completed. After adding hydrochloric acid methanol solution for quenching, filtering, washing and vacuum drying in turn, polyisoprene is obtained; wherein the reactivity can be up to 10 ⁸ g/mol(Fe)/h, cis-1,4/trans- The selectivity of 1,4 is (99:1) to (1:99). The method of the invention can be suitable for the preparation of rubber materials with different properties; the method and application are constructed for the development of high-performance and special-performance polymer materials. In addition, the catalytic system provided by the invention has strong heat resistance, and can maintain high activity even at a high temperature of 100° C., so that the industrial application prospect of this type of catalyst is better.

Description

A kind of high-efficiency and controllable method for preparing polyisoprene

technical field

The invention belongs to the field of conjugated diene catalytic polymerization, in particular to a method for efficiently and controllably preparing polyisoprene.

Background technique

Polyisoprene, which is formed by the polymerization of isoprene monomer under the action of a catalyst, is an important synthetic rubber. According to different unit structures, polyisoprene can be divided into polyisoprene with cis-1,4 structure, polyisoprene with trans-1,4 structure, 1,2- and 3,4- Polyisoprene, the specific structure is as follows:

Polymers with different selectivity have different applications. In isoprene polymerization, titanium-based catalysis and rare-earth catalysis systems have been studied most deeply. However, titanium-based catalysts have wide molecular weight distribution and complex active species; rare earth metals are expensive, and catalyst costs are high. This series of factors limit its further application. As an emerging cheap green catalyst, Fe catalyst has great potential in regulating the molecular weight, molecular weight distribution and selectivity of polymerization. However, the problems faced by iron-based catalysts are low activity, uncontrollable selectivity, sensitive main catalyst and short life. , easily deactivated.

SUMMARY OF THE INVENTION

In order to solve the technical problems of low activity of the existing iron-based catalyst, uncontrollable selectivity and sensitive and easy deactivation of the catalyst, the present invention provides a method for preparing polyisoprene with high efficiency and controllability.

An efficient and controllable method for preparing polyisoprene of the present invention is carried out according to the following steps:

Under an inert gas atmosphere, the isoprene monomer, rigid framework iron complex, cocatalyst and solvent were added to the reactor, and the reaction was stirred at -40 to 100 ° C for 12 s to 120 min. After the reaction, a methanol solution of hydrochloric acid was added to quench it. After filtration, washing and vacuum drying, polyisoprene was obtained; the reactivity was up to 10 ⁸ g/mol(Fe)/h, and the selectivity of cis-1,4/trans-1,4 It is (99:1)～(1:99).

Further limited, the structural formula of the rigid framework iron complex is:

Further defined, the co-catalyst is MAO, Cl ₂ AlEt, ClAlEt ₂ , EASC, Al(i-Bu) ₃ or AlEt ₃ .

Further limited, the inert gas is nitrogen or argon.

Further limited, the solvent is toluene, petroleum ether, n-hexane, cyclohexane, dichloromethane, tetrahydrofuran or hydrogenated gasoline.

It is further defined that the molar ratio of the isoprene monomer to the iron complex with a rigid framework is (2500-20000):1.

Further limited, the molar ratio of the cocatalyst to the rigid framework iron complex is (5-1000):1.

Further limited, the molar ratio of the cocatalyst to the rigid framework iron complex is 500:1.

It is further limited that the ratio of the molar amount of the isoprene monomer to the volume of the solvent is (0.05-2) mol: 1L.

Further limited, the reaction was stirred at 25 °C for 10 min.

Further limited, the concentration of the methanol solution of hydrochloric acid is 1 mol/L.

Further limited, the feeding sequence is any one of the following three:

(1) dissolving cocatalyst, rigid framework iron complex and isoprene monomer into solvent successively;

(2) cocatalyst, isoprene monomer, rigid framework iron complex are dissolved in solvent successively;

(3) The rigid framework iron complex, the isoprene monomer and the cocatalyst are dissolved in the solvent in turn.

The remarkable effect that the present invention has compared with the prior art:

1) The main catalyst of the rigid pyridineimide iron complex catalyst system provided by the present invention is insensitive to air, and the catalytic system has extremely high activity [up to 10 ⁸ g·(mol of Fe) ^-1 ·h ^-1 ], and A polymer with high molecular weight (number average molecular weight is 30000-500000 g/mol, >10 ⁴ ), wide molecular weight distribution (PDI=1.8-7.0) and controllable microstructure are obtained. The selectivity of this type of system is not sensitive to the reaction temperature.

2) The preparation method of the present invention is easy to operate, and the selectivity can be adjusted (the selectivity of cis-1,4 can be well controlled at 0%-60% or the selectivity of trans-1,4 is 0-82%, and the selectivity of 1,2- The polymerization is controlled below 1%, and the 3,4-polymerization is controlled at 18-55%).

3) The method of the present invention is suitable for the preparation of rubber materials with different properties; the method and application are constructed for the development of high-performance and special-performance polymer materials.

4) The catalytic system provided by the present invention has strong heat resistance, and can maintain high activity even at a high temperature of 100° C., so that the industrial application prospect of this type of catalyst is better.

Detailed ways

Embodiment 1: The structural formula of the rigid framework iron complex 1a of this embodiment is:

Its specific synthesis method is as follows: add FeCl ₂ (146.4mg, 1.2mmol, 1.0equiv) to the single-necked flask of 100mL, then dissolve with 2mL glacial acetic acid, then add 6,7-dihydro-5H-quinoline-8- A solution of ketone (170.0 mg, 1.2 mmol, 1.0 equiv) and aniline (107.6 mg, 1.2 mmol, 1.0 equiv) in glacial acetic acid (8 mL) was refluxed at 130 °C for 12 hours, cooled to room temperature, and ether (50 mL) was added, A purple solid was precipitated; filtered and washed three times with 30 mL of diethyl ether to obtain a purple solid, the rigid framework iron complex 1a.

Result: Yield 53.9%.

Infrared analysis: FT-IR (KBr, disk, cm ^-1 ): 3060, 2948, 1623, 1585 (ν, C=N), 1486, 1450, 1335, 1202, 1130, 790,698.

Elemental Analysis: Anal. Calcd for C ₃₀ H ₂₈ Cl ₄ Fe ₂ N ₄ : C, 51.62%; H, 4.04%; N, 8.03%. Found: C, 51.24%; H, 3.65%; N, 7.83%.

High resolution mass spectrum: HRMS (TOF MS ES+): [M—FeCl ₃ ] ⁺ calcd for [C ₃₀ H ₂₈ ClFeN ₄ ] ⁺ m/z 535.1353, found m/z 535.1367.

Embodiment 2: The structural formula of the rigid framework iron complex 2a of this embodiment is:

Its specific synthesis method is as follows: add FeCl ₂ (86.1mg, 0.7mmol, 1.0equiv) to the single-necked flask of 100mL, then dissolve with 2mL glacial acetic acid; then add 6,7-dihydro-5H-quinoline-8- A solution of ketone (100.0 mg, 0.7 mmol, 1.0 equiv) and p-toluidine (72.8 mg, 0.7 mmol, 1.0 equiv) in glacial acetic acid (8 mL) was refluxed at 130 ° C for 12 hours, cooled to room temperature, and a large amount of ether ( 50 mL), a dark brown solid was precipitated; filtered, and washed with 30 mL of ether for 3 times to obtain a dark brown solid, that is, the rigid framework iron complex 2a.

Result: Yield 60.6%.

Infrared analysis: FT-IR (KBr, disk, cm ^-1 ): 2943, 1578 (ν, C=N), 1505, 14551357, 1337, 1219, 1110, 837, 791,770.

Elemental Analysis: Anal. Calcd for [C ₃₂ H ₃₂ Cl ₄ Fe ₂ N ₄ ][CH ₃ COOH][H ₂ O]: C, 50.78%; H, 4.76%; N, 6.97%. Found: C, 50.03 %; H, 3.85%; N, 6.96%.

High resolution mass spectrum: HRMS (TOF MS ES+): [M—FeCl ₃ ] ⁺ calcd for [C ₃₂ H ₃₂ ClFeN ₄ ] ⁺ m/z 563.1666, found m/z 563.1669.

Embodiment 3: The structural formula of the rigid framework iron complex 3a of this embodiment is:

Its specific synthesis method is as follows: add FeCl ₂ (99.0mg, 0.8mmol, 1.0equiv) to the single-necked flask of 100mL, then dissolve with 2mL glacial acetic acid; then add 6,7-dihydro-5H-quinoline-8- A solution of ketone (115.0 mg, 0.8 mmol, 1.0 equiv) and 1-naphthylamine (111.9 mg, 0.8 mmol, 1.0 equiv) in glacial acetic acid (8 mL) was refluxed at 130 ° C for 12 hours, cooled to room temperature, and a large amount of ether was added (50 mL), a gray-brown solid was precipitated; filtered, and washed three times with 30 mL of ether to obtain a gray-brown solid, ie, the rigid framework iron complex 3a.

Result: Yield 51.6%.

Infrared analysis: FT-IR (KBr, disk, cm ^-1 ): 3054, 2942, 1626, 1583 (ν, C=N), 1452, 1390, 1333, 1285, 1216, 1130, 781.

Elemental Analysis: Anal. Calcd for [C ₃₈ H ₃₂ Cl ₄ Fe ₂ N ₄ ][3H ₂ O]: C, 53.56%; H, 4.49%; N, 6.57%. Found: C, 52.87%; H, 3.80 %; N, 6.56%.

High resolution mass spectrum: HRMS (TOF MS ES+): [M—FeCl ₃ ] ⁺ calcd for [C ₃₈ H ₃₂ ClFeN ₄ ] ⁺ m/z 635.1666, found m/z 635.1671.

Embodiment 4: The structural formula of the rigid framework iron complex 4a of this embodiment is:

Its specific synthesis method is as follows: add FeCl ₂ (86.1mg, 0.7mmol, 1.0equiv) to the single-necked flask of 100mL, then dissolve with 2mL glacial acetic acid; then add 6,7-dihydro-5H-quinoline-8- A solution of ketone (100.0mg, 0.7mmol, 1.0equiv) and 2,6-diisopropylaniline (87.8mg, 0.7mmol, 1.0equiv) in glacial acetic acid (8mL) was refluxed at 130°C for 12 hours, cooled to At room temperature, a large amount of diethyl ether (50 mL) was added, and an orange-red solid was precipitated; filtered, and washed with 30 mL of diethyl ether for three times to obtain an orange-red solid, ie, the rigid framework iron complex 4a.

Result: Yield 57.9%.

Infrared analysis: FT-IR (KBr, disk, cm ^-1 ): 2961, 2868, 1618, 1582 (ν, C=N), 1460, 1215, 1129, 1044, 926, 778, 770, 661.

Elemental analysis: Anal.Calcd for [C ₄₂ H ₅₂ ClFeN ₄ ·FeCl ₄ ]: C, 55.94%; H, 5.81%; N, 6.21%. Found: C, 55.50%; H, 5.56%; N, 6.38% .

High resolution mass spectrum: HRMS (TOF MS ES+): (M—FeCl ₄ ) ⁺ calcd for [C ₄₂ H ₅₂ Cl ₅ Fe ₂ N ₄ ] ⁺ m/z 703.3231, found m/z 703.3227.

Embodiment 5: The structural formula of the rigid framework iron complex 5a of this embodiment is:

Its specific synthesis method is as follows: add FeCl ₂ (56.0mg, 0.4mmol, 1.0equiv) to the single-necked flask of 100mL, then dissolve with 2mL glacial acetic acid; then add 6,7-dihydro-5H-quinoline-8- A solution of ketone (65.0 mg, 0.4 mmol, 1.0 equiv) and 2,4,6-triphenylaniline (142.0 mg, 0.4 mmol, 1.0 equiv) in glacial acetic acid (8 mL) was refluxed at 130 °C for 12 hours, cooled After reaching room temperature, a large amount of ether (50 mL) was added, and a brown solid was precipitated; it was filtered, and washed with 30 mL of ether three times to obtain a brown solid, ie, the rigid framework iron complex 5a.

Result: Yield 70.2%.

Infrared analysis: FT-IR (KBr, disk, cm ^-1 ): 2923, 1659, 1588 (ν, C=N), 1456, 1429, 1356, 1207, 1112, 826, 759, 702.

Elemental Analysis: Anal. Calcd for _{C33H26Cl2FeN2 :} C, _{68.65 ;} H, 4.54; N, 4.85%. Found: C, 68.93; H, 4.28; N, 4.59%.

High resolution mass spectrum: HRMS (TOF MS ES+): [M-Cl] ⁺ calcd for [C ₃₃ H ₂₆ ClFeN ₂ ] ⁺ m/z 541.1135, found 541.1149.

Embodiment 6: The structural formula of the rigid framework iron complex 6a of this embodiment is:

Its specific synthesis method is as follows: add FeCl ₂ (86.1mg, 0.7mmol, 1.0equiv) to the single-necked flask of 100mL, then dissolve with 2mL glacial acetic acid; then add 6,7-dihydro-5H-quinoline-8- A solution of ketone (100.0 mg, 0.7 mmol, 1.0 equiv) and 2,6-xylyl-4-methylaniline (289.2 mg, 0.7 mmol, 1.0 equiv) in glacial acetic acid (8 mL) was refluxed at 130 °C for 12 hours, cooled to room temperature, added a large amount of ether (50 mL), a dark brown solid was precipitated; filtered, and washed with 30 mL of ether three times to obtain a dark brown solid, ie, the rigid framework iron complex 6a.

Result: Yield 71.0%.

Infrared analysis: FT-IR (KBr, disk, cm ^-1 ): 3028, 2926, 2030, 1589 (ν, C=N), 1571, 1445, 1206, 1022, 834,726.

Elemental Analysis: Anal. Calcd for _{C42H36Cl2FeN2 :} C, _{72.53 ;} H, 5.22; N, 4.03%. Found: C, 72.61; H, 5.37; N, 4.16%.

High resolution mass spectrum: HRMS (TOF MS ES+): [M-Cl] ⁺ calcd for [C ₄₂ H ₃₆ ClFeN ₂ ] ⁺ m/z 659.1911, found 659.1909.

Embodiment 7: The specific steps of a method for efficiently and controllably preparing polyisoprene of the present embodiment are as follows:

Under an argon atmosphere, MAO (4 mmol, 500 equiv.), 5 mL of toluene, isoprene monomer (20 mmol, 2500 equiv.), and rigid framework iron complex 1a (8 μmol, 1 equiv.) were sequentially added to a 25 mL Schlenk tube. The reaction was stirred at 25°C for 10 min. After the reaction was completed, 1M hydrochloric acid methanol solution was added to quench it. The viscous polymer solution was poured into 50 mL of ethanol to allow the polymer to settle out. The filtrate was removed by filtration, and the obtained solid matter was washed three times with ethanol. , and then placed in a vacuum drying oven to dry to constant weight at 40 °C to obtain polyisoprene.

Result: Yield >99.0%. The reaction selectivity was 52% cis-1,4,3% trans-1,4 and 45% 3,4-polyisoprene, _Mn was 127,000 g/mol, and PDI was 2.6.

Embodiment 8: The specific steps of a method for efficiently and controllably preparing polyisoprene of the present embodiment are as follows:

Under an argon atmosphere, MAO (0.4 mmol, 50 equiv.), 5 mL of toluene, isoprene monomer (20 mmol, 2500 equiv.), and a rigid framework iron complex 1a (8 μmol, 1 equiv.) were sequentially added to a 25 mL Schlenk tube. ), stirred and reacted at 25°C for 10min, added 1M hydrochloric acid methanol solution to quench after the reaction, poured the viscous polymer solution into 50mL of ethanol, allowed the polymer to settle out, filtered to remove the filtrate, and the obtained solid matter was washed with ethanol three times, and then placed in a vacuum drying oven at 40° C. to dry to constant weight to obtain polyisoprene. Result: Yield >99.0%. The reaction selectivity was 53% cis-1,4 and 47% 3,4-polyisoprene, _Mn was 32,000 g/mol, and PDI was 2.3.

Specific embodiment nine: a kind of efficient and controllable method for preparing polyisoprene of the present embodiment The specific steps are as follows:

Under an argon atmosphere, MAO (0.04 mmol, 5 equiv.), 5 mL of toluene, isoprene monomer (20 mmol, 2500 equiv.), and a rigid framework iron complex 1a (8 μmol, 1 equiv.) were sequentially added to a 25 mL Schlenk tube. ), stirred and reacted at 25°C for 10min, added 1M hydrochloric acid methanol solution to quench after the reaction, poured the viscous polymer solution into 50mL of ethanol, allowed the polymer to settle out, filtered to remove the filtrate, and the obtained solid matter was washed with ethanol three times, and then placed in a vacuum drying oven at 40° C. to dry to constant weight to obtain polyisoprene.

Result: Yield >99.0%. The selectivity of the reaction was 52% cis-1,4 and 48% 3,4-polyisoprene, _Mn was 93,000 g/mol, and PDI was 1.9.

Specific embodiment ten: a kind of efficient and controllable method for preparing polyisoprene of the present embodiment The specific steps are as follows:

Under an argon atmosphere, MAO (100 μmol, 50 equiv.), 5 mL of toluene, isoprene monomer (20 mmol, 10000 equiv.), and rigid framework iron complex 1a (2 μmol, 1 equiv.) were sequentially added to a 25 mL Schlenk tube. The reaction was stirred at 25°C for 10 min. After the reaction was completed, 1M hydrochloric acid methanol solution was added to quench it. The viscous polymer solution was poured into 50 mL of ethanol to allow the polymer to settle out. The filtrate was removed by filtration, and the obtained solid matter was washed three times with ethanol. , and then placed in a vacuum drying oven to dry to constant weight at 40 °C to obtain polyisoprene.

Result: Yield >99.0%. The reaction selectivity was 52% cis-1,4 and 48% 3,4-polyisoprene, _Mn was 130,000 g/mol, and PDI was 2.1.

Embodiment 11: The specific steps of a method for efficiently and controllably preparing polyisoprene of the present embodiment are as follows:

Under an argon atmosphere, MAO (100 μmol, 100 equiv.), 5 mL of toluene, isoprene monomer (20 mmol, 20000 equiv.), and rigid framework iron complex 1a (1 μmol, 1 equiv.) were sequentially added to a 25 mL Schlenk tube. , stirred and reacted at 25°C for 60min, after the reaction was completed, 1M hydrochloric acid methanol solution was added to quench, the viscous polymer solution was poured into 50mL of ethanol, the polymer was allowed to settle out, the filtrate was removed by filtration, and the obtained solid matter was washed three times with ethanol , and then placed in a vacuum drying oven to dry to constant weight at 40 °C to obtain polyisoprene.

Result: Yield >99.0%. The reaction selectivity was 52% cis-1,4, 2% trans-1,4 and 46% 3,4-polyisoprene, _Mn was 305,000 g/mol, and PDI was 2.2.

Specific embodiment twelve: a kind of high-efficiency and controllable method for preparing polyisoprene of the present embodiment The specific steps are as follows:

Under an argon atmosphere, MAO (50 μmol, 50 equiv.), 5 mL of toluene, isoprene monomer (20 mmol, 20000 equiv.), and rigid framework iron complex 1a (1 μmol, 1 equiv.) were sequentially added to a 25 mL Schlenk tube. , stirred and reacted at 25°C for 60min, after the reaction was completed, 1M hydrochloric acid methanol solution was added to quench, the viscous polymer solution was poured into 50mL of ethanol, the polymer was allowed to settle out, the filtrate was removed by filtration, and the obtained solid matter was washed three times with ethanol , and then placed in a vacuum drying oven to dry to constant weight at 40 °C to obtain polyisoprene.

Result: The yield was 90%. The reaction selectivity was 52% cis-1,4 and 48% 3,4-polyisoprene, _Mn was 94,000 g/mol, and PDI was 2.0.

Specific embodiment thirteen: a kind of high-efficiency and controllable method for preparing polyisoprene of the present embodiment The specific steps are as follows:

Under an argon atmosphere, MAO (4 mmol, 500 equiv.), 5 mL of toluene, isoprene monomer (20 mmol, 2500 equiv.), and rigid framework iron complex 1a (8 μmol, 1 equiv.) were sequentially added to a 25 mL Schlenk tube. The reaction was stirred at 25°C for 1 min. After the reaction was completed, 1M hydrochloric acid methanol solution was added to quench it. The viscous polymer solution was poured into 50 mL of ethanol to allow the polymer to settle out. The filtrate was removed by filtration, and the obtained solid matter was washed three times with ethanol. , and then placed in a vacuum drying oven to dry to constant weight at 40 °C to obtain polyisoprene.

Result: Yield >99.0%. The reaction selectivity was 53% cis-1,4, 2% trans-1,4 and 45% 3,4-polyisoprene, _Mn was 93,000 g/mol, and PDI was 2.5.

Specific embodiment fourteen: a kind of high-efficiency and controllable method for preparing polyisoprene of the present embodiment The specific steps are as follows:

Under an argon atmosphere, MAO (4 mmol, 1000 equiv.), 5 mL of toluene, isoprene monomer (20 mmol, 5000 equiv.), and rigid framework iron complex 1a (4 μmol, 1 equiv.) were sequentially added to a 25 mL Schlenk tube. , stir the reaction at 25°C for 12s, add 1M hydrochloric acid methanol solution to quench after the reaction, pour the viscous polymer solution into 50mL of ethanol, make the polymer settle out, remove the filtrate by filtration, and wash the obtained solid material with ethanol three times , and then placed in a vacuum drying oven to dry to constant weight at 40 °C to obtain polyisoprene.

Results: Yield >99.0%, polymerization activity was 1.02×10 ⁸ g/(mol of Fe)/h. The reaction selectivity was 54% cis-1,4 and 46% 3,4-polyisoprene, _Mn was 122,000 g/mol, and PDI was 2.7.

Specific embodiment fifteen: a kind of efficient and controllable method for preparing polyisoprene of the present embodiment The specific steps are as follows:

Under an argon atmosphere, MAO (4 mmol, 500 equiv.), 5 mL of toluene, isoprene monomer (20 mmol, 2500 equiv.), and rigid framework iron complex 1a (8 μmol, 1 equiv.) were sequentially added to a 25 mL Schlenk tube. , stirred and reacted at 50 ° C for 10 min. After the reaction was completed, 1M hydrochloric acid methanol solution was added to quench, and the viscous polymer solution was poured into 50 mL of ethanol to allow the polymer to settle out. The filtrate was removed by filtration, and the obtained solid matter was washed three times with ethanol. , and then placed in a vacuum drying oven to dry to constant weight at 40 °C to obtain polyisoprene.

Result: Yield >99.0%. The reaction selectivity was 43% cis-1,4, 14% trans-1,4 and 43% 3,4-polyisoprene, _Mn was 97,000 g/mol, and PDI was 2.5.

Specific embodiment sixteen: a kind of high-efficiency and controllable method for preparing polyisoprene of the present embodiment The specific steps are as follows:

Under an argon atmosphere, MAO (4 mmol, 500 equiv.), 5 mL of toluene, isoprene monomer (20 mmol, 2500 equiv.), and rigid framework iron complex 1a (8 μmol, 1 equiv.) were sequentially added to a 25 mL Schlenk tube. , stirred and reacted at 75 ° C for 10 min, after the reaction was completed, 1M hydrochloric acid methanol solution was added to quench, the viscous polymer solution was poured into 50 mL of ethanol, the polymer was allowed to settle out, the filtrate was removed by filtration, and the obtained solid matter was washed three times with ethanol , and then placed in a vacuum drying oven to dry to constant weight at 40 °C to obtain polyisoprene.

Result: Yield >99.0%. The reaction selectivity was 42% cis-1,4, 19% trans-1,4 and 39% 3,4-polyisoprene, _Mn was 69,000 g/mol, and PDI was 2.3.

Specific embodiment seventeen: a kind of efficient and controllable method for preparing polyisoprene of the present embodiment The specific steps are as follows:

Under an argon atmosphere, MAO (4 mmol, 500 equiv.), 5 mL of toluene, isoprene monomer (20 mmol, 2500 equiv.), and rigid framework iron complex 1a (8 μmol, 1 equiv.) were sequentially added to a 25 mL Schlenk tube. , stirred and reacted at 100 ° C for 10 min. After the reaction was completed, 1M hydrochloric acid methanol solution was added for quenching. The viscous polymer solution was poured into 50 mL of ethanol to allow the polymer to settle out. The filtrate was removed by filtration, and the obtained solid matter was washed three times with ethanol. , and then placed in a vacuum drying oven to dry to constant weight at 40 °C to obtain polyisoprene.

Result: Yield >99.0%. The reaction selectivity was 40% cis-1,4, 22% trans-1,4 and 38% 3,4-polyisoprene, _Mn was 64,000 g/mol, and PDI was 2.2.

Specific embodiment eighteen: a kind of high-efficiency and controllable method for preparing polyisoprene of the present embodiment The specific steps are as follows:

Under an argon atmosphere, MAO (4 mmol, 500 equiv.), 5 mL of toluene, isoprene monomer (20 mmol, 2500 equiv.), and rigid framework iron complex 1a (8 μmol, 1 equiv.) were sequentially added to a 25 mL Schlenk tube. The reaction was stirred at 25 °C for 2 h. After the reaction was completed, 1M hydrochloric acid methanol solution was added to quench. The viscous polymer solution was poured into 50 mL of ethanol to allow the polymer to settle out. The filtrate was removed by filtration, and the obtained solid matter was washed three times with ethanol. , and then placed in a vacuum drying oven to dry to constant weight at 40 °C to obtain polyisoprene.

Result: Yield >99.0%. The reaction selectivity was 54% cis-1,4, 2% trans-1,4 and 44% 3,4-polyisoprene, _Mn was 108,000 g/mol, and PDI was 2.2.

Embodiment 19: The difference between this embodiment and Embodiment 18 is: the rigid framework iron complex 2a, and other steps and parameters are the same as those of Embodiment 18.

Result: Yield >99.0%. The reaction selectivity was 43% cis-1,4, 2% trans-1,4 and 55% 3,4-polyisoprene, _Mn was 227,000 g/mol, and PDI was 1.9.

Embodiment 20: The difference between this embodiment and the eighteenth embodiment is that the rigid framework iron complex 3a, other steps and parameters are the same as those of the eighteenth embodiment.

Result: Yield >99.0%. The reaction selectivity was 58% cis-1,4, 2% trans-1,4 and 40% 3,4-polyisoprene, _Mn was 61,000 g/mol, and PDI was 3.7.

Embodiment 21: The difference between this embodiment and the eighteenth embodiment is that the rigid framework iron complex 4a, other steps and parameters are the same as those of the eighteenth embodiment.

Result: Yield 6.1%. The reaction selectivity was 54% cis-1,4, 11% trans-1,4 and 35% 3,4-polyisoprene, _Mn was 30,000 g/mol, and PDI was 2.8.

Embodiment 22: The difference between this embodiment and the eighteenth embodiment is that the rigid framework iron complex 5a, other steps and parameters are the same as those of the eighteenth embodiment.

Result: Yield >99.0%. The reaction selectivity was 50% cis-1,4, 18% trans-1,4 and 32% 3,4-polyisoprene, _Mn was 28,000 g/mol, and PDI was 6.9.

Embodiment 23: The difference between this embodiment and the eighteenth embodiment is that the rigid framework iron complex 6a, other steps and parameters are the same as those of the eighteenth embodiment.

Result: Yield 59.7%. The reaction selectivity was 82% trans-1,4 and 18% 3,4-polyisoprene, _Mn was 23,000 g/mol, and PDI was 6.9.

Claims (9)

1. a method for controllable preparation of polyisoprene, is characterized in that, this preparation method is carried out according to the following steps: Under an inert gas atmosphere, the isoprene monomer, rigid framework iron complex, cocatalyst and solvent were added to the reactor, and the reaction was stirred at -40 to 100 ° C for 12 s to 120 min. After the reaction, a methanol solution of hydrochloric acid was added to quench it. After filtration, washing, and vacuum drying, polyisoprene was obtained; the reactivity was up to 10 ⁸ g/mol(Fe)/h, and the selectivity of cis-1,4/trans-1,4 was (99:1)～(1:99), the structural formula of the rigid framework iron complex is:

2. a kind of controllable method for preparing polyisoprene according to claim 1, is characterized in that, described cocatalyst is MAO, Cl ₂ AlEt, ClAlEt ₂ , EASC, Al(i-Bu) ₃ or AlEt ₃ . 3 . The method for controllable preparation of polyisoprene according to claim 1 , wherein the inert gas is nitrogen or argon. 4 . 4. a kind of controllable method for preparing polyisoprene according to claim 1, is characterized in that, described solvent is that solvent is toluene, petroleum ether, n-hexane, cyclohexane, methylene chloride, tetrahydrofuran or Hydrogenated gasoline. 5. a kind of method for controllable preparation of polyisoprene according to claim 1, is characterized in that, the mol ratio of described isoprene monomer and rigid skeleton iron complex is (2500～20000): 1. 6 . The method for controllable preparation of polyisoprene according to claim 1 , wherein the molar ratio of the cocatalyst to the iron complex with a rigid framework is (5-1000):1. 7 . 7 . The method for controllable preparation of polyisoprene according to claim 1 , wherein the molar ratio of the cocatalyst to the rigid framework iron complex is 500:1. 8 . 8 . The method for controllable preparation of polyisoprene according to claim 1 , wherein the ratio of the molar amount of the isoprene monomer to the volume of the solvent is (0.05～2) mol 8 . : 1L. 9 . The method for controllable preparation of polyisoprene according to claim 1 , wherein the reaction is stirred at 25° C. for 10 min. 10 .