A method for preparing syndiotactic polystyrene

Abstract

The application discloses a preparation method of syndiotactic polystyrene, and the preparation method comprises the following steps: under the action of a rare earth complex with a structure of formula I, a cocatalyst and an organic solvent, styrene monomers are subjected to a polymerization reaction to obtain the syndiotactic polystyrene; and the preparation method of the syndiotactic polystyrene can realize high activity and high syndiotactic polymerization of the styrene.

Description

Technical Field

[0001] This invention relates to a method for preparing polystyrene, and more particularly to a method for preparing syndiotactic polystyrene, belonging to the field of polymer materials technology. Background Technology

[0002] In 1985, Ishihara et al. in Japan successfully synthesized syndiotactic polystyrene for the first time. Its melting point is as high as 270℃, and its crystallization rate is extremely fast (two orders of magnitude faster than isotactic polystyrene). In addition to possessing all the advantages of atactic polystyrene, syndiotactic polystyrene also exhibits high elastic modulus, high heat resistance, strong solvent resistance, and chemical resistance, comparable to engineering plastics. Furthermore, it possesses properties not found in other engineering plastics, such as low density and low dielectric constant. It has broad application prospects in automotive electrical components, consumer electronics, and industrial films. Therefore, the preparation of syndiotactic polystyrene has attracted widespread research interest.

[0003] In 2004, Professor Hou Zhaomin's research group first used monoceramic rare earth metal complexes to catalyze the polymerization of styrene to prepare syndiotactic polystyrene. In 2012, Professor Cui Dongmei's research group developed rare earth metal complexes with restricted geometric configurations containing coordinating nitrogen and carbon atom side arms, successfully achieving highly syndiotactic selective polymerization of styrene. Numerous past studies have shown that Lewis bases containing coordinating oxygen atoms in the catalytic system, such as tetrahydrofuran, significantly reduce or even deactivate the activity of rare earth metal complexes in syndiotactic polymerization of styrene (Organometallics 2013, 32, 5, 1445; ACS Catal. 2016, 6, 176). Therefore, when preparing rare earth metal complexes, ligands with high coordination numbers and large steric hindrance should be selected to avoid coordination with Lewis bases containing oxygen atoms.

[0004] Organometallics (2013, 32, 5, 1445) prepared a series of semi-cenotropic rare-earth metal catalysts with Lewis bases containing coordinating oxygen atoms, such as amino and tetrahydrofurans. A drawback of this technique, or relative to the present invention, is that the presence of Lewis bases with coordinating oxygen atoms in the catalytic system leads to a significant reduction, or even deactivation, of the activity of rare-earth metal complexes in catalyzing the syndiotactic polymerization of styrene.

[0005] ACS Catal. 2016, 6, 176 synthesized a series of rare earth metal catalysts with restricted geometries, and found that the catalytic activity gradually increased as the size of the rare earth metal atoms decreased. A drawback of this technique, or a limitation of this invention, is that the presence of Lewis bases with coordinated oxygen atoms in the catalytic system leads to a significant decrease, or even deactivation, of the activity of rare earth metal complexes in catalyzing the syndiotactic polymerization of styrene.

[0006] CN201711172220.2 discloses a binuclear rare earth catalyst and its preparation method, as well as a polymerization method for syndiotactic polystyrene. The catalyst contains the general formula [(R2LnLLnR2)(S). n The reaction mixture is a trivalent dinuclear rare earth complex; wherein L is a cyclopentadienyl derivative, indenyl, indenyl derivative, fluorenyl, fluorenyl derivative, or amidyl derivative bridged with ferrocene; Ln is a rare earth metal; R is an alkyl, amino, or halogen group connected to a rare earth metal; S is selected from diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, or tetramethylethylenediamine; 0≤n≤4. Styrene monomer and solvent are added to a reactor under an inert atmosphere and heated to 0℃~80℃; the dinuclear rare earth catalyst is dissolved in the solvent to prepare a catalyst solution with a concentration of 0.01~0.05mol / L, and added to the reaction system together with an organoboron salt compound. The polymerization reaction is carried out at 0℃~80℃ for 1~10min. After the reaction is completed, the precipitate is filtered and dried to obtain syndiotactic polystyrene.

[0007] CN201810478634.6 discloses a rare earth catalyst and its preparation method, as well as a syndiotactic polymerization method for styrene. The catalyst has the following structural formula: where Ln is a rare earth metal; R is an alkyl, amino, or halogen group connected to the rare earth metal; B is an alkyl group having 1-10 carbon atoms, an alkyl group having 1-10 carbon atoms and several silicon atoms, or an alkyl group having 1-10 carbon atoms and several halogen atoms; D is N, P, or As; R' is hydrogen, methyl, ethyl, isopropyl, or tert-butyl; R" is an aryl or alkyl group containing various substituents. Styrene monomer and a third solvent are added to a reactor under an inert atmosphere, and the temperature is controlled between 0℃ and 80℃. The rare earth catalyst is dissolved in the solvent to prepare a catalyst solution with a concentration of 0.01-0.1 mol / L, which is then added to the reaction system along with an organoboron salt compound. The polymerization reaction is carried out at 0℃ to 80℃ for 2-20 hours. After the reaction is complete, the precipitate is filtered and dried to obtain syndiotactic polystyrene.

[0008]

[0009] CN200310108170.3 discloses a catalyst for the preparation of syndiotactic polystyrene. The technical solution effectively solves this problem by employing a metallocene titanium compound with the general structural formula R1Ti(O-C6H4-NO2)3, where R1 is cyclopentadienyl or pentamethylcyclopentadienyl, C6H4 is phenyl, and Ti is bonded to the phenyl group by an oxygen atom, along with alkylaluminoxanes and alkylaluminum compounds, to form a syndiotactic polymerization catalyst for styrene. This catalyst can be used in the industrial production of syndiotactic polymerization of styrene. A sealed 100 mL two-necked flask with a feeding port and a gas inlet tube is vacuum-dried to remove oxygen. Under nitrogen protection, MAO, styrene, triisobutylaluminum, and the titanium compound are added sequentially. The mixture is magnetically stirred at 30°C for 10 minutes, then the temperature is raised to 90°C for polymerization for 2 hours. The reaction is terminated with a 10% HCl ethanol solution to obtain the polymer. Summary of the Invention

[0010] The purpose of this invention is to provide a method for preparing syndiotactic polystyrene, which can achieve highly active and highly syndiotactic polymerization of styrene.

[0011] To achieve the above objectives, the present invention provides a method for preparing syndiotactic polystyrene, the method comprising: under anhydrous and oxygen-free conditions, in the presence of a rare earth complex having the structure of Formula I, a co-catalyst, and an organic solvent, polymerizing styrene monomer to obtain syndiotactic polystyrene;

[0012]

[0013] Wherein, R1 is a cyclopentadienyl group having the structure of formula II and its derivatives, an indenyl group having the structure of formula III and its derivatives, or a fluorenyl group having the structure of formula IV and its derivatives.

[0014]

[0015] R2 and R3 are independently selected from hydrogen, methyl, ethyl, isopropyl, tert-butyl, phenyl, 2,6-dimethylphenyl, 4-methylphenyl, mestrimethylphenyl, 2,6-diisopropylphenyl, 2,4,6-triisopropylphenyl or 2,6-di-tert-butylphenyl, more preferably hydrogen, methyl, ethyl, isopropyl, tert-butyl, phenyl, 2,6-dimethylphenyl, 2,6-diisopropylphenyl, 2,4,6-triisopropylphenyl or 2,6-di-tert-butylphenyl;

[0016] Ln is Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb or Lu; more preferably Sc, Y, La, Nd, Gd, Tb, Dy, Ho, Er, Tm, Yb or Lu, and most preferably Sc, Y, La, Nd, Gd, Er, Tm or Lu.

[0017] R4 is a C1-C20 alkyl, C1-C20 alkylsilyl, C1-C20 alkylamino, borohydride or allyl; more preferably it is a C1-C20 alkyl, C1-C20 alkylsilyl, borohydride or allyl, and most preferably it is a C1-C20 alkylsilyl, borohydride or allyl.

[0018] E is C, Si, or Ge;

[0019] X is tetrahydrofuran, diethyl ether, ethylene glycol dimethyl ether, or toluene;

[0020] m = 1 or 2; n = 0, 1 or 2, more preferably n = 0 or 1. In the method for preparing syndiotactic polystyrene of the present invention, the co-catalyst is an aluminoxane compound, a combination of an aluminoxane compound and an alkylaluminum compound, or a combination of an organoboron salt and an alkylaluminum compound.

[0021] Preferably, the aluminum oxane compound is at least one of methylaluminoxane, trimethylaluminoxane, ethylaluminoxane, n-propylaluminoxane, and n-butylaluminoxane; the alkylaluminum compound is at least one of alkylaluminum, hydrogenated alkylaluminum, and alkylaluminum chloride; and the organoboron salt is [Ph3C][B(C6F5)4], [Ph3C][BPh4], [PhNMe2H][BPh4], [PhNMe2H][B(C6F5)4], BPh3, or B(C6F5)3.

[0022] Preferably, the molar ratio of the styrene monomer to the rare earth complex is (200-10000):1.

[0023] Preferably, the molar ratio of the organoboron salt to the rare earth complex is (0.5 to 10.0):1.

[0024] Preferably, the molar ratio of the alkylaluminum compound to the rare earth complex is (1-2000):1.

[0025] Preferably, the molar ratio of the aluminoxane compound to the rare earth complex is (1-2000):1.

[0026] In the preparation method of syndiotactic polystyrene of the present invention, the organic solvent is tetrahydrofuran, pyridine, n-hexane or ethylene glycol dimethyl ether, more preferably tetrahydrofuran.

[0027] The method for preparing syndiotactic polystyrene of the present invention involves a polymerization reaction at a temperature of -60 to 80°C for a time of 1 to 30 minutes.

[0028] The present invention also provides a rare earth complex having the structure of Formula I.

[0029]

[0030] Wherein, R1 is a cyclopentadienyl group having the structure of formula II and its derivatives, an indenyl group having the structure of formula III and its derivatives, or a fluorenyl group having the structure of formula IV and its derivatives.

[0031]

[0032] R2 and R3 are independently selected from hydrogen, methyl, ethyl, isopropyl, tert-butyl, phenyl, 2,6-dimethylphenyl, 4-methylphenyl, mestrimethylphenyl, 2,6-diisopropylphenyl, 2,4,6-triisopropylphenyl or 2,6-ditert-butylphenyl;

[0033] Ln can be Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, or Lu;

[0034] R4 is a C1-C20 alkyl, C1-C20 alkylsilyl, C1-C20 alkylamino, borohydride, or allyl group;

[0035] E is C, Si, or Ge;

[0036] X is tetrahydrofuran, diethyl ether, ethylene glycol dimethyl ether or toluene, more preferably tetrahydrofuran;

[0037] m = 1 or 2; n = 0, 1 or 2.

[0038] This invention also provides a method for preparing rare earth complexes having the structure of Formula I, comprising the following steps:

[0039] A1) Under anhydrous and oxygen-free conditions, a ligand having the structure of formula V, an alkyl lithium and an organic solvent are mixed and reacted to obtain the first reaction mixture;

[0040] A2) The first reaction mixture above and the rare earth halide undergo a second reaction to obtain a second reaction mixture;

[0041] A3) The above second reaction mixture is reacted with a substituent-containing compound to obtain a rare earth complex having the structure of Formula I.

[0042]

[0043] Wherein, R1 is a cyclopentadienyl group having the structure of formula II and its derivatives, an indenyl group having the structure of formula III and its derivatives, or a fluorenyl group having the structure of formula IV and its derivatives.

[0044]

[0045] R2 and R3 are independently selected from hydrogen, methyl, ethyl, isopropyl, tert-butyl, phenyl, 2,6-dimethylphenyl, 4-methylphenyl, mestrimethylphenyl, 2,6-diisopropylphenyl, 2,4,6-triisopropylphenyl or 2,6-ditert-butylphenyl;

[0046] E is C, Si, or Ge;

[0047] m = 1 or 2;

[0048] The present invention relates to a method for preparing rare earth complexes having a structure of Formula I, wherein the substituent compound is a rare earth compound containing an alkyl group, a compound containing an allyl group, or a compound containing a borohydride group.

[0049] The present invention relates to a method for preparing rare earth complexes having a structure of Formula I, wherein the rare earth element in the rare earth halide is Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, or Lu, and the halogen is chlorine.

[0050] In the preferred embodiment of the method for preparing rare earth complexes having the structure of Formula I of the present invention, the alkyl group in the alkyl lithium is methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, silanylamino, dimethylamino, diethylamino, dipropylamino, N,N-dimethylaminophenyl, trimethylsilylmethyl, bistrimethylsilylmethyl, o-methylmercaptophenyl, o-dimethylphosphinophenyl, tetrahydroboryl, methoxy, ethoxy, isopropoxy, n-propoxy, n-butoxy, sec-butoxy, or tert-butoxy.

[0051] In the method for preparing rare earth complexes having the structure of Formula I of the present invention, preferably, the organic solvent is tetrahydrofuran, pyridine, n-hexane or ethylene glycol dimethyl ether, more preferably tetrahydrofuran.

[0052] The method for preparing rare earth complexes having the structure of Formula I of the present invention, wherein the molar ratio of alkyl lithium to ligand having the structure of Formula V is (1-1.2):1.

[0053] The method for preparing rare earth complexes with Formula I of the present invention, wherein the molar ratio of the rare earth halide to the ligand with Formula V is (1-1.2):1.

[0054] The method for preparing rare earth complexes having the structure of Formula I of the present invention, wherein the molar ratio of the substituent compound to the ligand having the structure of Formula V is (2-2.4):1.

[0055] The present invention relates to a rare earth complex having a structure of Formula I and a method for its preparation. The synthesis method of the rare earth complex is simple, and the yield is as high as 50-95%. The polymerization catalytic system catalyzes the syndiotactic polymerization of styrene, exhibiting the characteristic of controlled polymerization.

[0056] The method for preparing syndiotactic styrene provided by this invention employs a catalyst combination comprising an eta5-coordinated rare earth complex and one or more co-catalysts. The rare earth complex exhibits eta5 coordination of cyclopentadienyl (cyclopentadienyl and its derivatives, indene and its derivatives, and fluorenyl and its derivatives) and electron-withdrawing effects of nitrogen-containing aromatic rings, as well as oxygen atoms coordinating to the central metal, thus restricting the space of the central metal. Therefore, during the catalytic polymerization of syndiotactic styrene, selective insertion of styrene monomers can be achieved, and syndiotactic polystyrene with different molecular weights can be obtained by changing the feed ratio. In the preparation of syndiotactic styrene provided by this invention, the monomer conversion rate can reach up to 100%, the degree of syndiotacticity (rrrr) can reach up to 100%, the number-average molecular weight of the polymer is adjustable between 84,000 and 935,000 depending on the styrene-to-catalyst feed ratio, the molecular weight distribution can reach as low as 1.21, and the melting point is in the range of 266–273°C. Attached Figure Description

[0057] Figure 1 The 1H NMR spectrum of the rare earth complex with the structure of Formula 5 prepared in this invention. Detailed Implementation

[0058] The following provides a detailed description of the embodiments of the present invention: These embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and processes. However, the scope of protection of the present invention is not limited to the following embodiments. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions.

[0059] In this invention, there are no other special restrictions on the selection of substituents; R1 to R4 can all be selected independently, and R2 and R3 can be the same or different. This invention does not particularly limit the use of cyclopentadienyl groups and their derivatives having the structure of Formula II, indenyl groups and their derivatives having the structure of Formula III, or fluorenyl groups and their derivatives having the structure of Formula IV; any cyclopentadienyl groups and their derivatives, indenyl groups and their derivatives, or fluorenyl groups and their derivatives well known to those skilled in the art can be used. The solvent molecule described in this invention is coordinated to a rare earth complex.

[0060] The present invention does not impose any particular restrictions on the selection and combination of substituents in the rare earth complexes having the structure of Formula I. The selection and combination methods known to those skilled in the art are acceptable. The present invention preferably has rare earth complexes having Formulas 1 to 20, wherein the complexes shown in Formulas 1 to 12 are rare earth complexes in which R4 is alkylsilyl or alkylamine, the complexes shown in Formulas 13 to 17 are rare earth complexes in which R4 is allyl, and the complexes shown in Formulas 18 to 20 are rare earth complexes in which R4 is borohydride.

[0061]

[0062] This invention first involves reacting a ligand having a V-structure, alkyllithium, and an organic solvent under anhydrous and oxygen-free conditions to obtain a first reaction mixture. The alkyllithium is preferably composed of methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, silanylamino, dimethylamino, diethylamino, dipropylamino, N,N-dimethylaminophenyl, trimethylsilylmethyl, bis(trimethylsilylmethyl), o-methylmercaptophenyl, o-dimethylphosphinophenyl, tetrahydroboryl, methoxy, ethoxy, isopropoxy, n-propoxy, n-butoxy, sec-butoxy, or tert-butoxy, more preferably n-butyl, N,N-dimethylaminophenyl, or trimethylsilyl. The methyl group, bis(trimethylsilyl)methyl group, and most preferably n-butyl group are used. The molar ratio of the alkyllithium to the ligand having the V structure is preferably (1-1.2):1, more preferably (1:1.15):1. The volume ratio of the organic solvent to the ligand having the V structure is preferably (4-6) L:1 mol, more preferably (4.5-5.5) L:1 mol. The reaction time is preferably 0.8-1.5 hours, more preferably 0.8-1.2 hours, and most preferably 1 hour. The reaction temperature is preferably -78℃ to 40℃, more preferably -50℃ to 30℃, and most preferably -10℃ to 20℃.

[0063] In order to stabilize the reaction temperature, the present invention preferably dissolves alkyllithium in a second organic solvent first. In order to enable the ligand to participate in the reaction better, the ligand having the V structure is preferably dissolved in the organic solvent first, and then the second organic solvent containing alkyllithium is added to carry out the reaction, and finally the first reaction mixture is obtained. In the second organic solvent containing alkyllithium, the concentration of alkyllithium is preferably 1.0 to 2.0 mol / L, more preferably 1.2 to 1.8 mol / L.

[0064] This invention does not impose any particular limitation on the organic solvent; any organic solvent well known to those skilled in the art is acceptable, preferably tetrahydrofuran, pyridine, n-hexane, or ethylene glycol dimethyl ether, more preferably tetrahydrofuran. This invention also does not impose any particular limitation on the second organic solvent; any organic solvent well known to those skilled in the art is acceptable, preferably tetrahydrofuran, pyridine, n-hexane, or ethylene glycol dimethyl ether, more preferably n-hexane. The organic solvent and the second organic solvent in this invention can be the same or different, without any particular limitation. This invention does not impose any particular limitation on the anhydrous and oxygen-free conditions; any anhydrous and oxygen-free conditions well known to those skilled in the art are acceptable. In this invention, it is preferred to obtain oxygen-free conditions by introducing an inert gas or nitrogen gas, more preferably by introducing nitrogen gas. This invention does not impose any particular limitation on other reaction conditions; any reaction conditions of this type well known to those skilled in the art are acceptable.

[0065] The present invention does not particularly limit the source of the ligands having the above-mentioned V-structure, and they can be prepared by synthetic methods well known to those skilled in the art. Preferably, the preparation is carried out in accordance with the following literature (H.Miao, S.Wang, S.Zhou, Y.Wei, Z.Zhou, H.Zhu, S.Wu, H.Wang, Inorganica Chimica Acta, 2010, 363, 1325-1331).

[0066] The present invention involves reacting the first reaction mixture obtained in the above steps with a rare earth halide to obtain a second reaction mixture. The rare earth element in the rare earth halide is preferably Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, or Lu, more preferably Y, La, Gd, Er, or Lu. The molar ratio of the rare earth halide to the ligand shown in Formula V is preferably (1–1.2):1, more preferably (1.05–1.15):1. The reaction time for the second reaction is preferably 3–5 hours, more preferably 3.5–4.5 hours, and most preferably 4 hours. The present invention does not impose any particular limitation on the rare earth halide; any rare earth halide well known to those skilled in the art is acceptable, preferably a rare earth trichloride. The present invention does not impose any particular limitation on other reaction conditions; any reaction conditions of this type well known to those skilled in the art are acceptable.

[0067] Finally, the second reaction mixture obtained in the above steps is reacted with a substituent-containing compound in a third reaction to obtain a rare earth complex having the structure of Formula I.

[0068] The substituent in the substituent-containing compound of the present invention is substituent R4 in the rare earth complex having the structure of Formula I; the molar ratio of the substituent-containing compound to the ligand having the structure of Formula V is preferably (2-2.4):1, more preferably (2-2.2):1; the temperature of the third reaction is preferably room temperature; the reaction time is preferably 10-14 hours, more preferably 11-13 hours, and most preferably 12 hours; the substituent-containing compound is preferably a rare earth compound containing an alkyl group, an allyl compound, or a borohydride compound; in the rare earth compound containing an alkyl group, the alkyl group is preferably a C1-C20 alkyl group, a C1-C20 alkylsilyl group, or a C1-C20 alkylamine group; the allyl compound is preferably an allyl Grignard reagent or an allyl derivative Grignard reagent, wherein the allyl Grignard reagent is more preferably C3H5MgCl, and the allyl derivative Grignard reagent is preferably C3H5MgCl. nR5MgCl; n is preferably 3 or 4; R5 is preferably an aliphatic group, an alicyclic group, a phenyl group, or a substituted phenyl group of C1 to C20; the substituted phenyl group is preferably an aliphatic group, an alicyclic group, or an aromatic group substituted with a phenyl group of C1 to C20; the present invention does not have a particular limitation on room temperature, and any room temperature known to those skilled in the art is acceptable, preferably 20 to 30°C; the present invention does not have a particular limitation on the definition of the above-mentioned rare earth compounds containing alkyl groups, allyl compounds, and borohydride compounds, and any concept known to those skilled in the art is acceptable, namely rare earth alkyl compounds, allyl compounds, and borohydride compounds.

[0069] After the third reaction is completed, the present invention preferably removes the solvent and extracts and concentrates the product with toluene to obtain a rare earth complex having the structure of Formula I. The present invention does not particularly limit the method of solvent removal, and any solvent removal method known to those skilled in the art is acceptable. The present invention does not particularly limit the conditions of toluene extraction, and any toluene extraction conditions known to those skilled in the art are acceptable. The present invention does not particularly limit the method of concentration, and any concentration method known to those skilled in the art is acceptable.

[0070] The present invention also preferably provides a method for preparing a rare earth complex having the structure of Formula I, comprising:

[0071] Under anhydrous and oxygen-free conditions, a ligand having the structure of formula V, a rare earth alkyl compound, and an organic solvent are mixed and reacted to obtain a rare earth complex having the structure of formula I.

[0072]

[0073] Wherein, R1 is a cyclopentadienyl group having the structure of formula II and its derivatives, an indenyl group having the structure of formula III and its derivatives, or a fluorenyl group having the structure of formula IV and its derivatives.

[0074]

[0075] R2 and R3 are independently selected from hydrogen, methyl, ethyl, isopropyl, tert-butyl, phenyl, 2,6-dimethylphenyl, 4-methylphenyl, mestrimethylphenyl, 2,6-diisopropylphenyl, 2,4,6-triisopropylphenyl or 2,6-ditert-butylphenyl;

[0076] E is C, Si, or Ge;

[0077] m = 1 or 2;

[0078] In the rare earth alkyl compound, the rare earth element is Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb or Lu;

[0079] The rare earth alkyl compounds include C1-C20 alkyl compounds, C1-C20 alkylsilyl compounds, and C1-C20 alkylamine compounds;

[0080] The organic solvent is tetrahydrofuran, diethyl ether, pyridine, or ethylene glycol dimethyl ether.

[0081] The substituent in the substituent-containing compound of the present invention is R4 in the rare earth complex of formula I; the molar ratio of the rare earth alkyl compound to the ligand having the formula V structure is preferably (2-2.4):1, more preferably (2-2.2):1; the reaction temperature is preferably room temperature; the reaction time is preferably 10-14 h, more preferably 11-13 h, and most preferably 12 h; the alkyl group is preferably a C1-C20 alkyl group, a C1-C20 alkylsilyl group, or a C1-C20 alkylamine group, more preferably CH3, CH2CH3, CH(CH3)2, C(CH3)3, CH2SiMe2, CH(SiMe3)2, or CH2(o-C6H4(NMe2)).

[0082] In the preparation method of the rare earth complex with Formula I provided by the present invention, the meanings of R1 to R3, Z, and m, as well as the preferred principles, are consistent with those in the rare earth complex with Formula I provided by the present invention, and will not be repeated here. In the preparation method of the rare earth complex with Formula I provided by the present invention, the preferred schemes related to the preparation method of the rare earth complex with Formula I provided by the present invention are consistent with those in the previous preparation method of the rare earth complex with Formula I, and will not be repeated here.

[0083] This invention also provides a method for preparing syndiotactic polystyrene, characterized by comprising:

[0084] Under anhydrous and oxygen-free conditions, styrene monomers are polymerized in the presence of rare earth complexes with Formula I, co-catalysts, and organic solvents to obtain syndiotactic polystyrene.

[0085] The cocatalyst is an aluminoxane compound, a combination of an aluminoxane compound and an alkylaluminum compound, or a combination of an organoboron salt and an alkylaluminum compound.

[0086] This invention provides a method for preparing syndiotactic polystyrene. The method employs a catalyst combination comprising an eta5-coordinated rare earth complex and one or more co-catalysts. The rare earth complex, due to the eta5 coordination of cyclopentadienyl (cyclopentadienyl and its derivatives, indenyl and its derivatives, and fluorenyl and its derivatives) and the electron-withdrawing effect of the nitrogen-containing aromatic ring, as well as the presence of oxygen atoms coordinating to the central metal, restricts the space of the central metal. Therefore, during the catalytic polymerization of syndiotactic polystyrene, selective insertion of styrene monomers can be achieved, and by changing the feed amount, syndiotactic polystyrene with different molecular weights can be obtained.

[0087] This invention describes a polymerization reaction of styrene monomers under anhydrous and oxygen-free conditions, in the presence of a rare earth complex having the structure of Formula I, a co-catalyst, and an organic solvent, to obtain syndiotactic polystyrene.

[0088] The co-catalyst is preferably a combination of an aluminum oxane compound, an aluminum oxane compound, and an alkyl aluminum compound, or a combination of an organoboron salt and an alkyl aluminum compound; the alkyl aluminum compound is preferably an alkyl aluminum, a hydrogenated alkyl aluminum, or an alkyl aluminum chloride, more preferably trimethylaluminum, triethylaluminum, tri-n-propylaluminum, tri-n-butylaluminum, triisopropylaluminum, triisobutylaluminum, tripentylaluminum, trihexylaluminum, tricyclohexylaluminum, trioctylaluminum, triphenylaluminum, tri-p-tolylaluminum, tribenzylaluminum, ethyl dibenzylaluminum, ethyl di-p-tolylaluminum, diethylbenzylaluminum, dimethylaluminum hydride, diethylaluminum hydride, di-n-propylaluminum hydride, di- n-Butylaluminum hydride, diisopropylaluminum hydride, diisobutylaluminum hydride, dipentylaluminum hydride, dihexylaluminum hydride, dicyclohexylaluminum hydride, dioctylaluminum hydride, diphenylaluminum hydride, di-p-tolylaluminum hydride, dibenzylaluminum hydride, ethylbenzylaluminum hydride, ethyl-p-tolylaluminum hydride, dimethylaluminum chloride, diethylaluminum chloride, di-n-propylaluminum chloride, di-n-butylaluminum chloride, diisopropylaluminum chloride, diisobutylaluminum chloride, dipentylaluminum chloride, dihexylaluminum chloride, dicyclohexylaluminum chloride, dioctylaluminum chloride, diphenylaluminum chloride, di-p-tolylaluminum chloride, dibenzylaluminum chloride, ethylbenzylaluminum chloride The organoboron salt is preferably methylaluminum, trimethylaluminum, triethylaluminum, triisobutylaluminum, diisobutylaluminum hydride, or diethylaluminum chloride; the organoboron salt is preferably [Ph3C][B(C6F5)4], [Ph3C][BPh4], [PhNMe2H][BPh4], [PhNMe2H][B(C6F5)4], BPh3, or B(C6F5)3, more preferably [Ph3C][B(C6F5)4], BPh3, or [P [h3C][BPh4]; the aluminum oxane compound is preferably an alkyl aluminum oxane, more preferably a methyl aluminum oxane, dried methyl aluminum oxane, or modified methyl aluminum oxane, and most preferably a methyl aluminum oxane or modified methyl aluminum oxane; the present invention does not particularly limit the dried methyl aluminum oxane, and the definition of dried methyl aluminum oxane known to those skilled in the art is sufficient, that is, methyl aluminum oxane does not contain methyl aluminum; the present invention does not particularly limit the modified methyl aluminum oxane, and the definition of modified methyl aluminum oxane known to those skilled in the art is sufficient, that is, methyl aluminum oxane contains isobutyl aluminum.

[0089] The molar ratio of the organoboron salt to the rare earth complex having Formula I is preferably (0.5–10.0):1, more preferably (1.0–5.0):1, and most preferably (1.0–3.0):1; the molar ratio of the alkylaluminum compound to the rare earth complex having Formula I is preferably (1–2000):1, more preferably (1–100):1, and most preferably (5–50):1; the molar ratio of the methylaluminoxane to the rare earth complex having Formula I is (1–2000):1, more preferably (1–100):1, and most preferably (5–50):1; the molar ratio of the styrene monomer to the rare earth complex having Formula I is (200–10000):1, more preferably (500–8000):1.

[0090] The preferred temperature for the polymerization reaction is -60 to 80°C, more preferably -30 to 50°C. The present invention does not impose any particular limitation on the organic solvent, and any organic solvent known to those skilled in the art for such reactions may be used, preferably a C5 to C8 hydrocarbon solvent, more preferably pentane, hexane, toluene or xylene.

[0091] To ensure the stable progress of the polymerization reaction, this invention preferably first mixes a rare earth complex with the structure of Formula I, a co-catalyst, and an organic solvent to form a catalyst combination, and then adds a monomer to carry out the polymerization reaction. In the catalyst combination, the molar concentration of the rare earth complex with the structure of Formula I is preferably 0.2 mmol / L to 2.0 mmol / L, more preferably 0.5 mmol / L to 1.8 mmol / L. The catalyst combination of this invention comprises three forms: (1) a rare earth complex, an organoboron salt, and an alkylaluminum compound; (2) a rare earth complex, an aluminum oxane, and an alkylaluminum compound; (3) a rare earth complex and an aluminum oxane. The catalyst is a coordination catalytic system containing multiple compounds. The rare earth complex is a rare earth complex with the structure of Formula I, which is a compound with a restricted geometric configuration.

[0092] The present invention does not impose any particular restrictions on the order of feeding in the above-mentioned preparation method of syndiotactic polystyrene; the order of feeding in copolymer polymerization reactions known to those skilled in the art can be used.

[0093] Under anhydrous and oxygen-free conditions, styrene monomer is added to a catalyst combination formed by a rare earth complex having the structure of Formula I, a co-catalyst, and an organic solvent, and syndiotactic polystyrene is obtained after a set time. The polymerization reaction time is 1 to 30 minutes, more preferably 1 to 10 minutes; the polymerization reaction temperature is preferably -60 to 80°C, more preferably -30 to 50°C; the present invention does not particularly limit other conditions of the above polymerization reaction, and conditions of catalytic polymerization reactions well known to those skilled in the art can be used.

[0094] To further understand the present invention, the preparation method of syndiotactic polystyrene provided by the present invention will be described in detail below with reference to embodiments.

[0095] Preparation of rare earth complexes shown in Formulas 1 to 20

[0096] Preparation of rare earth complexes shown in Formula 1

[0097] Under anhydrous and oxygen-free conditions, a ligand (0.5 mmol) with R1 being indene, E being C, R2 and R3 being hydrogen, and m=1, as shown in Formula V, was stirred with Y(CH2SiMe3)2(THF)2 in tetrahydrofuran for 12 hours. The solvent was then removed to obtain a rare earth complex (0.22 g) with the structure of Formula 1.

[0098] Preparation of rare earth complexes as shown in Formula 2

[0099] Under anhydrous and oxygen-free conditions, a rare earth complex (0.26 g) with the structure of Formula 2 was obtained by preparing a rare earth complex with the structure shown in Formula 1 using the method of preparing Lu(CH2SiMe3)2(THF)2 (0.5 mmol) with R1 being indanyl, E being C, R2 and R3 being hydrogen and m=1.

[0100] Preparation of rare earth complexes as shown in Formula 3

[0101] Under anhydrous and oxygen-free conditions, a rare earth complex (0.26 g) with the structure of Formula 3 was obtained by preparing a rare earth complex with R1 as indanyl, E as C, R2 and R3 as hydrogen and m=1, and Er(CH2SiMe3)2(THF)2 (0.5 mmol) as shown in Formula V.

[0102] Preparation of rare earth complexes as shown in Formula 4

[0103] Under anhydrous and oxygen-free conditions, a rare earth complex with the structure of Formula 4 (0.23 g, Yield: 75%) was prepared by reacting a ligand (R1 = indenyl, E = C, R2 and R3 = hydrogen, m = 1) shown in Formula V with Gd(CH2SiMe3)2(THF)2 (0.5 mmol) and Gd(CH2SiMe3)2(THF)2 (0.5 mmol).

[0104] Preparation of rare earth complexes as shown in Formula 5

[0105] Under anhydrous and oxygen-free conditions, a rare earth complex (0.25 g) with the structure of Formula 5 was prepared by reacting a ligand (0.5 mmol) of Formula V (where R1 is fluorenyl, E is C, R2 and R3 are hydrogen, and m=1) with Y(CH2SiMe3)2(THF)2 (0.5 mmol).

[0106] The rare earth complexes with the structure of Formula 5 were subjected to proton nuclear magnetic resonance spectroscopy analysis, such as... Figure 1 As shown.

[0107] Preparation of rare earth complexes as shown in Formula 6

[0108] Under anhydrous and oxygen-free conditions, a rare earth complex (0.27 g) with the structure of Formula 6 was obtained by preparing a rare earth complex with Lu(CH2SiMe3)2(THF)2 (0.5 mmol) with R1 being fluorenyl, E being C, R2 and R3 being hydrogen and m=1.

[0109] Preparation of rare earth complexes as shown in Formula 7

[0110] Under anhydrous and oxygen-free conditions, a tetrahydrofuran solution of a ligand (0.5 mmol) of a ligand with R1 being indenyl, E being C, R2 and R3 being methyl, and m=1 as shown in Formula V was reacted with n-butyllithium (0.32 mL, 1.6 M n-hexane solution) at 0 °C for 1 hour to obtain a lithium salt of the first reaction mixture ligand. At room temperature, a tetrahydrofuran solution of the above lithium salt was added dropwise to a tetrahydrofuran suspension of LaCl3 (0.5 mmol) and reacted for 4 hours to obtain a rare earth chloride of the second reaction mixture. Li(o-CH2C6H4NMe2) (1.0 mmol) was added to the above rare earth chloride and reacted for 12 hours. After removing the solvent and extracting and concentrating with toluene, a rare earth complex (0.24 g) with the structure of Formula 7 was obtained.

[0111] Preparation of rare earth complexes as shown in Formula 8

[0112] Under anhydrous and oxygen-free conditions, a rare earth complex (0.27 g) with the structure shown in Formula 7 was prepared by reacting a ligand (0.5 mmol) of Formula V (where R1 is indenyl, E is C, R2 and R3 are hydrogen, and m=1) with n-butyllithium (0.32 mL, 1.6 M n-hexane solution), LaCl3 (0.5 mmol), and Li(o-CH2C6H4NMe2) (1.0 mmol).

[0113] Preparation of rare earth complexes as shown in Formula 9

[0114] Under anhydrous and oxygen-free conditions, a rare earth complex (0.25 g) with the structure of Formula 9 was prepared by reacting a ligand (0.5 mmol) of Formula V (R1 being 3,6-di-tert-butylfluorenyl, E being C, R2 and R3 being hydrogen, m=1) with n-butyllithium (0.32 mL, 1.6 M n-hexane solution), LaCl3 (0.5 mmol), and Li(o-CH2C6H4NMe2) (1.0 mmol).

[0115] Preparation of rare earth complexes as shown in Formula 10

[0116] Under anhydrous and oxygen-free conditions, a rare earth complex (0.24 g) with the structure of Formula 10 was prepared by reacting a ligand (0.5 mmol) of Formula V (R1 being fluorenyl, E being Si, R2 and R3 being methyl, m=1) with n-butyllithium (0.32 mL, 1.6 M n-hexane solution), YCl3 (0.5 mmol), and Li(o-CH2C6H4NMe2) (1.0 mmol) with the ligand of Formula V (R1 being fluorenyl, E being Si, R2 and R3 being methyl) with the ligand of Formula V (R1 being fluorenyl, E being Si, R2 and R3 being methyl) with the ligand of Formula V (R1 being fluorenyl, E being Si, R2 and R3 being methyl) with the ligand of Formula V (R1 being fluorenyl, E being methyl) with the ligand of Formula V (R2 ...

[0117] Preparation of rare earth complexes as shown in Formula 11

[0118] Under anhydrous and oxygen-free conditions, a rare earth complex (0.25 g) with the structure of Formula 11 was prepared by reacting a ligand (0.5 mmol) of Formula V (R1 being fluorenyl, E being C, R2 and R3 being hydrogen, m=1) with n-butyllithium (0.32 mL, 1.6 M n-hexane solution), YCl3 (0.5 mmol), and Li(o-CH2C6H4NMe2) (1.0 mmol).

[0119] Preparation of rare earth complexes as shown in Formula 12

[0120] Under anhydrous and oxygen-free conditions, a rare earth complex (0.27 g) with the structure of Formula 12 was prepared by reacting a ligand (0.5 mmol) of Formula V (R1 being fluorenyl, E being C, R2 and R3 being hydrogen, m=1) with n-butyllithium (0.32 mL, 1.6 M n-hexane solution), LuCl3 (0.5 mmol), and Li(o-CH2C6H4NMe2) (1.0 mmol) as shown in Formula 7.

[0121] Preparation of rare earth complexes as shown in Formula 13

[0122] Under anhydrous and oxygen-free conditions, a rare earth complex with the structure of Formula 13 (0.16 g, Yield: 69%) was prepared by reacting a ligand (0.5 mmol) of Formula V (where R1 is fluorenyl, E is C, R2 and R3 are hydrogen, and m=1) with n-butyllithium (0.32 mL, 1.6 M n-hexane solution), YCl3 (0.5 mmol), and CH2CHCH2MgBr (1.0 mmol).

[0123] Preparation of rare earth complexes as shown in Formula 14

[0124] Under anhydrous and oxygen-free conditions, a rare earth complex (0.11 g) with the structure of Formula 14 was prepared by reacting a ligand (0.5 mmol) of Formula V (R1 being indenyl, E being C, R2 and R3 being hydrogen, m=1) with n-butyllithium (0.32 mL, 1.6 M n-hexane solution), GdCl3 (0.5 mmol), and CH2CHCH2MgBr (1.0 mmol) with indole (R1 being indole, E being C, R2 and R3 being hydrogen) with m=1.

[0125] Preparation of rare earth complexes as shown in Formula 15

[0126] Under anhydrous and oxygen-free conditions, a rare earth complex (0.19 g) with the structure of Formula 15 was prepared by reacting a ligand (0.5 mmol) of Formula V (R1 being indenyl, E being C, R2 and R3 being hydrogen, m=1) with n-butyllithium (0.32 mL, 1.6 M n-hexane solution), LaCl3 (0.5 mmol), and CH2CHCH2MgBr (1.0 mmol) with indole (R1 being indole, E being C, R2 and R3 being hydrogen) with m=1.

[0127] Preparation of rare earth complexes as shown in Formula 16

[0128] Under anhydrous and oxygen-free conditions, a rare earth complex (0.17 g) with the structure of Formula 16 was prepared by reacting a ligand (0.5 mmol) of Formula V (R1 being indenyl, E being C, R2 and R3 being hydrogen, m=1) with n-butyllithium (0.32 mL, 1.6 M n-hexane solution), YCl3 (0.5 mmol), and CH2CHCH2MgBr (1.0 mmol) with indole (R1 being indole, E being C, R2 and R3 being hydrogen) with m=1.

[0129] Preparation of rare earth complexes as shown in Formula 17

[0130] Under anhydrous and oxygen-free conditions, a rare earth complex (0.20 g) with the structure of Formula 17 was prepared by reacting a ligand (0.5 mmol) of Formula V (R1 being indenyl, E being C, R2 and R3 being hydrogen, m=1) with n-butyllithium (0.32 mL, 1.6 M n-hexane solution), LuCl3 (0.5 mmol), and CH2CHCH2MgBr (1.0 mmol) with Indene (R1 being C, E being C, R2 and R3 being hydrogen) with m=1.

[0131] Preparation of rare earth complexes as shown in Formula 18

[0132] Under anhydrous and oxygen-free conditions, a rare earth complex (0.12 g) with the structure shown in Formula 7 was prepared by reacting a ligand (0.5 mmol) of Formula V (R1 being fluorenyl, E being C, R2 and R3 being hydrogen, m=1) with n-butyllithium (0.32 mL, 1.6 M n-hexane solution), YCl3 (0.5 mmol), and NaBH4 (1.0 mmol).

[0133] Preparation of rare earth complexes as shown in Formula 19

[0134] Under anhydrous and oxygen-free conditions, a rare earth complex (0.08 g) with the structure of Formula 19 was prepared by reacting a ligand (0.5 mmol) of Formula V (where R1 is tetramethylcyclopentadienyl, E is C, R2 and R3 are hydrogen, and m=1) with n-butyllithium (0.32 mL, 1.6 M n-hexane solution), LaCl3 (0.5 mmol), and NaBH4 (1.0 mmol).

[0135] Preparation of rare earth complexes as shown in Formula 20

[0136] Under anhydrous and oxygen-free conditions, a rare earth complex (0.16 g) with the structure of Formula 20 was prepared by reacting a ligand (0.5 mmol) of Formula V (where R1 is tetramethylcyclopentadienyl, E is C, R2 and R3 are hydrogen, and m=1) with n-butyllithium (0.32 mL, 1.6 M n-hexane solution), LuCl3 (0.5 mmol), and NaBH4 (1.0 mmol).

[0137] Preparation of catalyst assemblies:

[0138] Preparation of catalyst combination 1: At 25°C, 10 μmol of the rare earth complex shown in Formula 1, 10 μmol of [Ph3C][B(C6F5)4], 50 μmol of triisobutylaluminum, and toluene solvent were added to a 25 mL polymerization container that had been treated to be anhydrous and oxygen-free. The concentration of the rare earth complex in the catalyst combination was 2.0 mmol·L⁻¹. –1 The reaction was carried out for 2 minutes to obtain catalyst combination 1.

[0139] Preparation of catalyst combination 2: At 25°C, 10 μmol of the rare earth complex shown in Formula 2, 10 μmol of [Ph3C][B(C6F5)4], 100 μmol of triisobutylaluminum, and toluene solvent were added to a 25 mL polymerization container that had been treated with anhydrous and oxygen-free methods. The concentration of the rare earth complex in the catalyst combination was 0.67 mmol·L⁻¹. –1 The reaction was carried out for 2 minutes to obtain catalyst combination 2.

[0140] Preparation of catalyst combination 3: At 0°C, 10 μmol of the rare earth complex shown in Formula 2, 10 μmol of [Ph3C][B(C6F5)4], 100 μmol of triisobutylaluminum, and toluene solvent were added to a 25 mL polymerization container that had been treated with anhydrous and oxygen-free methods. The concentration of the rare earth complex in the catalyst combination was 0.67 mmol·L⁻¹. –1 After reacting for 2 minutes, catalyst combination 3 was obtained.

[0141] Preparation of catalyst combination 4: At -60℃, 10 μmol of the rare earth complex shown in Formula 2, 10 μmol of [Ph3C][B(C6F5)4], 100 μmol of triisobutylaluminum, and toluene solvent were added to a 25 mL polymerization container that had been treated with anhydrous and oxygen-free methods. The concentration of the rare earth complex in the catalyst combination was 0.67 mmol·L⁻¹. –1 After reacting for 2 minutes, catalyst combination 4 was obtained.

[0142] Preparation of catalyst combination 5: At 40°C, 10 μmol of the rare earth complex shown in Formula 2, 10 μmol of [Ph3C][B(C6F5)4], 100 μmol of triisobutylaluminum, and toluene solvent were added to a 25 mL polymerization container that had been treated with anhydrous and oxygen-free methods. The concentration of the rare earth complex in the catalyst combination was 0.67 mmol·L⁻¹. –1 After reacting for 2 minutes, catalyst combination 5 was obtained.

[0143] Preparation of catalyst combination 6: At 80 °C, 10 μmol of the rare earth complex shown in Formula 2, 10 μmol of [Ph3C][B(C6F5)4], 100 μmol of triisobutylaluminum, and toluene solvent were added to a 25 mL polymerization container that had been treated with anhydrous and oxygen-free methods. The concentration of the rare earth complex in the catalyst combination was 0.67 mmol·L⁻¹. –1 After reacting for 2 minutes, catalyst combination 6 was obtained.

[0144] Preparation of catalyst combination 7: At 25°C, 10 μmol of the rare earth complex shown in Formula 2, 20 μmol of dry methylaluminoxane, 100 μmol of trimethylaluminum, and xylene solvent were added to a 25 mL polymerization container that had been treated with anhydrous and oxygen-free methods. The concentration of the rare earth complex in the catalyst combination was 1.0 mmol·L⁻¹.–1 After reacting for 2 minutes, catalyst combination 7 was obtained.

[0145] Preparation of catalyst combination 8: At 25°C, 10 μmol of the rare earth complex shown in Formula 3, 10 μmol of [PhNHMe2][B(C6F5)4], 200 μmol of triethylaluminum, and toluene solvent were added to a 25 mL polymerization container that had been treated with anhydrous and oxygen-free methods. The concentration of the rare earth complex in the catalyst combination was 1.0 mmol·L⁻¹. –1 After reacting for 2 minutes, catalyst combination 8 was obtained.

[0146] Preparation of catalyst combination 9: At -40℃, 10 μmol of the rare earth complex shown in Formula 4, 10 μmol of [Ph3C][B(C6F5)4], 100 μmol of triisobutylaluminum, and toluene solvent were added to a 50 mL polymerization container that had been treated with anhydrous and oxygen-free methods. The concentration of the rare earth complex in the catalyst combination was 1.0 mmol·L⁻¹. –1 After reacting for 2 minutes, catalyst combination 9 was obtained.

[0147] Preparation of catalyst combination 10: At 25°C, 10 μmol of the rare earth complex shown in Formula 5, 100 μmol of methylaluminoxane, 100 μmol of triethylaluminum, and toluene solvent were added to a 250 mL polymerization container that had been treated to be anhydrous and oxygen-free. The concentration of the rare earth complex in the catalyst combination was 1.0 mmol·L⁻¹. –1 The reaction was carried out for 2 minutes to obtain catalyst combination 10.

[0148] Preparation of catalyst combination 11: At 25°C, 10 μmol of the rare earth complex shown in Formula 5, 10 μmol of [Ph3C][B(C6F5)4], 100 μmol of triisobutylaluminum, and toluene solvent were added to a 50 mL polymerization container that had been treated with anhydrous and oxygen-free methods. The concentration of the rare earth complex in the catalyst combination was 0.5 mmol·L⁻¹. –1 The reaction was carried out for 2 minutes to obtain catalyst combination 11.

[0149] Preparation of catalyst combination 12: At 60 °C, 10 μmol of the rare earth complex shown in Formula 6, 10 μmol of [PhNHMe2][B(C6F5)4], 1 mmol of triisobutylaluminum, and toluene solvent were added to a 25 mL polymerization container that had been treated with anhydrous and oxygen-free methods. The concentration of the rare earth complex in the catalyst combination was 1.0 mmol·L⁻¹. –1 After reacting for 2 minutes, catalyst combination 12 was obtained.

[0150] Preparation of catalyst combination 13: At 0°C, 10 μmol of the rare earth complex shown in Formula 7, 20 μmol of methylaluminoxane, and pentane solvent were added to 100 mL of anhydrous and oxygen-free polymerization container. The concentration of the rare earth complex in the catalyst combination was 0.2 mmol·L⁻¹. –1 After reacting for 2 minutes, catalyst combination 13 was obtained.

[0151] Preparation of catalyst combination 14: At 25°C, 10 μmol of the rare earth complex shown in Formula 8, 1000 μmol of methylaluminoxane, 300 μmol of trimethylaluminum, and hexane solvent were added to a 50 mL polymerization container that had been treated to be anhydrous and oxygen-free. The concentration of the rare earth complex in the catalyst combination was 0.2 mmol·L⁻¹. –1 After reacting for 2 minutes, catalyst combination 14 was obtained.

[0152] Preparation of catalyst combination 15: At 40°C, 10 μmol of the rare earth complex shown in Formula 9, 50 μmol of trimethylaluminoxane, 10 mmol of triisobutylaluminum, and hexane solvent were added to a 50 mL polymerization container that had been treated to be anhydrous and oxygen-free. The concentration of the rare earth complex in the catalyst combination was 0.25 mmol·L⁻¹. –1 The reaction was carried out for 2 minutes to obtain catalyst combination 15.

[0153] Preparation of catalyst combination 16: At 25°C, 10 μmol of the rare earth complex shown in Formula 10, 10 μmol of [Ph3C][BPh4], 10 mmol of triisobutylaluminum, and hexane solvent were added to a 50 mL polymerization container that had been treated with anhydrous and oxygen-free methods. The concentration of the rare earth complex in the catalyst combination was 0.2 mmol·L⁻¹. –1 The reaction was carried out for 2 minutes to obtain catalyst combination 16.

[0154] Preparation of catalyst combination 17: At 0 °C, 10 μmol of the rare earth complex shown in Formula 11, 20 μmol of [PhNHMe2][BPh4], 5 mmol of triisobutylaluminum, and hexane solvent were added to a 50 mL polymerization container that had been treated with anhydrous and oxygen-free methods. The concentration of the rare earth complex in the catalyst combination was 0.25 mmol·L⁻¹. –1 After reacting for 2 minutes, catalyst combination 17 was obtained.

[0155] Preparation of catalyst combination 18: At 80 °C, 10 μmol of the rare earth complex shown in Formula 12, 10 μmol of B(C6F5)3, 100 μmol of triisobutylaluminum, and hexane solvent were added to a 50 mL polymerization container that had been treated with anhydrous and oxygen-free methods. The concentration of the rare earth complex in the catalyst combination was 0.2 mmol·L⁻¹. –1 After reacting for 2 minutes, catalyst combination 18 was obtained.

[0156] Preparation of catalyst combination 19: At 25°C, 10 μmol of the rare earth complex shown in Formula 13, 10 mmol of methylaluminoxane, 500 μmol of triethylaluminum, and xylene solvent were added to a 50 mL polymerization container that had been treated to be anhydrous and oxygen-free. The concentration of the rare earth complex in the catalyst combination was 0.33 mmol·L⁻¹. –1 After reacting for 2 minutes, catalyst combination 19 was obtained.

[0157] Preparation of catalyst combination 20: At 0 °C, 10 μmol of the rare earth complex shown in Formula 14, 10 μmol of [Ph3C][B(C6F5)4], 500 μmol of triisobutylaluminum, and xylene solvent were added to a 50 mL polymerization container that had been treated with anhydrous and oxygen-free methods. The concentration of the rare earth complex in the catalyst combination was 0.25 mmol·L⁻¹. –1 The reaction was carried out for 2 minutes to obtain catalyst combination 20.

[0158] Preparation of catalyst combination 21: At 40 °C, 10 μmol of the rare earth complex shown in Formula 15, 10 μmol of [PhNHMe2][B(C6F5)4], 1 mmol of trimethylaluminum, and toluene solvent were added to a 50 mL polymerization container that had been treated with anhydrous and oxygen-free methods. The concentration of the rare earth complex in the catalyst combination was 0.33 mmol·L⁻¹. –1 After reacting for 2 minutes, catalyst combination 21 was obtained.

[0159] Preparation of catalyst combination 22: At 25°C, 10 μmol of the rare earth complex shown in Formula 16, 10 μmol of B(C6F5)3, 10 mmol of trimethylaluminum, and xylene solvent were added to a 25 mL polymerization container that had been treated with anhydrous and oxygen-free methods. The concentration of the rare earth complex in the catalyst combination was 0.25 mmol·L⁻¹. –1 After reacting for 2 minutes, catalyst combination 22 was obtained.

[0160] Preparation of catalyst combination 23: At –60°C, 10 μmol of the rare earth complex shown in Formula 17, 10 μmol of [Ph3C][BPh4], 1 mmol of triisobutylaluminum, and hexane solvent were added to a 50 mL polymerization container that had been treated with anhydrous and oxygen-free methods. The concentration of the rare earth complex in the catalyst combination was 0.25 mmol·L⁻¹. –1 After reacting for 2 minutes, catalyst combination 23 was obtained.

[0161] Preparation of catalyst combination 24: At 80 °C, 10 μmol of the rare earth complex shown in Formula 17, 10 μmol of [Ph3C][BPh4], 1 mmol of triisobutylaluminum, and toluene solvent were added to a 100 mL polymerization container that had been treated with anhydrous and oxygen-free methods. The concentration of the rare earth complex in the catalyst combination was 0.2 mmol·L⁻¹.–1 The reaction was carried out for 2 minutes to obtain catalyst combination 24.

[0162] Preparation of catalyst combination 25: At 0 °C, 10 μmol of the rare earth complex shown in Formula 18, 100 μmol of modified methylaluminoxane, 5 mmol of trimethylaluminum, and pentane solvent were added to a 50 mL polymerization container that had been treated to be anhydrous and oxygen-free. The concentration of the rare earth complex in the catalyst combination was 0.2 mmol·L⁻¹. –1 The reaction was carried out for 2 minutes to obtain catalyst combination 25.

[0163] Preparation of catalyst combination 26: At 25°C, 10 μmol of the rare earth complex shown in Formula 18, 100 μmol of modified methylaluminoxane, 5 mmol of trimethylaluminum, and hexane solvent were added to a 50 mL polymerization container that had been treated to be anhydrous and oxygen-free. The concentration of the rare earth complex in the catalyst combination was 0.2 mmol·L⁻¹. –1 After reacting for 2 minutes, catalyst combination 26 was obtained.

[0164] Preparation of catalyst combination 27: At 80 °C, 10 μmol of the rare earth complex shown in Formula 18, 10 μmol of [Ph3C][B(C6F5)4], 20 μmol of diisobutylaluminum hydride, and toluene solvent were added to a 25 mL polymerization container that had been treated with anhydrous and oxygen-free methods. The concentration of the rare earth complex in the catalyst combination was 0.67 mmol·L⁻¹. –1 The reaction was carried out for 2 minutes to obtain catalyst combination 27.

[0165] Preparation of catalyst combination 28: At 60°C, 10 μmol of the rare earth complex shown in Formula 18, 10 μmol of BPh3, 200 μmol of diethylaluminum chloride, and toluene solvent were added to a 25 mL polymerization container that had been treated with anhydrous and oxygen-free methods. The concentration of the rare earth complex in the catalyst combination was 0.5 mmol·L⁻¹. –1 After reacting for 2 minutes, catalyst combination 28 was obtained.

[0166] Preparation of catalyst combination 29: At 25°C, 10 μmol of the rare earth complex shown in Formula 19, 20 μmol of [Ph3C][BPh4], 200 μmol of diethylaluminum chloride, and hexane solvent were added to a 25 mL polymerization container that had been treated to be anhydrous and oxygen-free. The concentration of the rare earth complex in the catalyst combination was 0.28 mmol·L⁻¹. –1 After reacting for 2 minutes, catalyst combination 29 was obtained.

[0167] Preparation of catalyst combination 30: At 40°C, 10 μmol of the rare earth complex shown in Formula 20, 100 μmol of dry methylaluminoxane, 500 μmol of diisobutylaluminum hydride, and toluene solvent were added to a 25 mL polymerization container that had been treated to be anhydrous and oxygen-free. The concentration of the rare earth complex in the catalyst combination was 0.5 mmol·L⁻¹. –1 The reaction was carried out for 2 minutes to obtain catalyst combination 30.

[0168] Preparation of catalyst combination 31: At 0 °C, 10 μmol of the rare earth complex shown in Formula 20, 10 μmol of [Ph3C][B(C6F5)4], 500 μmol of triisobutylaluminum, and pentane solvent were added to a 50 mL polymerization container that had been treated with anhydrous and oxygen-free methods. The concentration of the rare earth complex in the catalyst combination was 0.2 mmol·L⁻¹. –1 After reacting for 2 minutes, coordination catalysis system 31 was obtained.

[0169] Preparation of catalyst combination 32: At -60℃, 10 μmol of the rare earth complex shown in Formula 20, 10 μmol of [PhNHMe2][BPh4], 2 mmol of trimethylaluminum, and pentane solvent were added to a 50 mL polymerization container that had been treated with anhydrous and oxygen-free methods. The concentration of the rare earth complex in the catalyst combination was 0.25 mmol·L⁻¹. –1 After reacting for 2 minutes, catalyst combination 32 was obtained.

[0170] Examples of styrene polymerization:

[0171] Example 1

[0172] 5 mL of toluene solution of catalyst combination 1 was placed in a polymerization flask that had been treated to be anhydrous and oxygen-free. 20 mmol of styrene monomer was added, and the polymerization reaction was carried out at 25 °C for 5 minutes. The polymerization reaction was terminated by adding 2 mL of ethanol solution with a volume concentration of 10% hydrochloric acid. The reaction solution was poured into 100 mL of methanol to precipitate, yielding syndiotactic polystyrene. This polymer was then dried in a vacuum drying oven for 48 hours to obtain syndiotactic polystyrene with a constant weight of 2.08 g. The total conversion rate was 1000%. The calculated polymerization activity was 2496·(mol / L) Y ·h) –1 Using nuclear magnetic carbon spectroscopy (NMR) 1 ¹³C NMR analysis showed that the content of syndiotactic polystyrene was >99%; GPC analysis showed that the molecular weight of syndiotactic polystyrene was 465,000 and the molecular weight distribution (Mw / Mn) was 1.4; DSC analysis showed that the melting point of syndiotactic polystyrene was 272℃.

[0173] Examples 2–32

[0174] Examples of the coordination catalytic system provided by the present invention in the polymerization of syndiotactic styrene are presented. The steps are the same as in Example 1, and the specific conditions and results are shown in Table 1.

[0175] Table 1 Synthesis of syndiotactic styrene by coordination polymerization method

[0176]

[0177]

[0178] From the polymerization data of Examples 1–32, it can be concluded that: through coordination polymerization, the catalyst combination provided by this invention can achieve highly active, highly syndiotactic polymerization of styrene, with an activity range of 520 kgmol / L. Ln -1 h -1 ~19980kgmol Ln -1 h -1 The syndiotacticity ranges from 80% to 100%. The prepared polystyrene has a number-average molecular weight of 84,000 to 935,000, a narrow molecular weight distribution (1.21-1.52), and a melting point of 266-273℃. The catalytic system exhibits good adaptability within a polymerization temperature range of -20 to 60℃, and the syndiotacticity of the polystyrene can reach up to 100%, with a narrow molecular weight distribution.

[0179] The above embodiments are typical examples listed to illustrate the technical solution of the present invention in detail. The present invention shall be subject to the protection scope of the claims and the invention content, and shall not be limited by the described embodiments. Simple substitutions or modifications to the present invention shall still be within the protection scope of the present invention.

Claims

1. A method for preparing syndiotactic polystyrene, characterized in that, include: Under anhydrous and oxygen-free conditions, styrene monomers are polymerized in the presence of rare earth complexes with Formula I, co-catalysts, and organic solvents to obtain syndiotactic polystyrene. Equation I; Wherein, R1 is a cyclopentadienyl group having the structure of formula II and its derivatives, an indenyl group having the structure of formula III and its derivatives, or a fluorenyl group having the structure of formula IV and its derivatives. Formula II, Formula III, Formula IV; R2 and R3 are independently selected from hydrogen and methyl, respectively; Ln can be Y, La, Gd, Tb, Er, or Lu; R4 is a C1-C20 alkyl, C1-C20 alkylsilyl, C1-C20 alkylamino, borohydride, or allyl group; E is either C or Si; X is tetrahydrofuran; m = 1; n = 0 or 1; The cocatalyst is an aluminoxane compound, a combination of an aluminoxane compound and an alkylaluminum compound, or a combination of an organoboron salt and an alkylaluminum compound.

2. The preparation method according to claim 1, characterized in that, The aluminum oxane compound is at least one of methylaluminoxane, trimethylaluminoxane, ethylaluminoxane, n-propylaluminoxane, and n-butylaluminoxane; the alkylaluminum compound is at least one of alkylaluminum, hydrogenated alkylaluminum, and alkylaluminum chloride; the organoboron salt is: [Ph3C][B(C6F5)4], [Ph3C][BPh4], [PhNMe2H][BPh4], [PhNMe2H][B(C6F5)4], BPh3, or B(C6F5)3.

3. The preparation method according to claim 1, characterized in that, The molar ratio of the styrene monomer to the rare earth complex is (200-10000):

1.

4. The preparation method according to claim 1, characterized in that, The molar ratio of the organoboron salt to the rare earth complex is (0.5–10.0):1; the molar ratio of the alkylaluminum compound to the rare earth complex is (1–2000):1; the molar ratio of the aluminoxane compound to the rare earth complex is (1–2000):

1.

5. The preparation method according to claim 1, characterized in that, The organic solvent is tetrahydrofuran, pyridine, n-hexane, or ethylene glycol dimethyl ether; the polymerization reaction is carried out at a temperature of -60 to 80°C for 1 to 30 minutes.

6. The preparation method according to claim 1, characterized in that, The preparation method of rare earth complexes with Formula I structure includes the following steps: A1) Under anhydrous and oxygen-free conditions, a ligand having the structure of formula V, an alkyl lithium and an organic solvent are mixed and reacted to obtain the first reaction mixture; A2) The first reaction mixture above is reacted with a rare earth halide to obtain a second reaction mixture; A3) The above second reaction mixture is reacted with a substituent-containing compound to obtain a rare earth complex having the structure of Formula I. Formula V.

7. The preparation method according to claim 6, characterized in that, The substituent compound is a rare earth compound containing an alkyl group, a compound containing an allyl group, or a compound containing a borohydride group.

8. The preparation method according to claim 6, characterized in that, In the rare earth halides, the rare earth elements are Y, La, Gd, Tb, Er, or Lu, and the halogen is chlorine.

9. The preparation method according to claim 6, characterized in that, In the alkyl lithium, the alkyl group is methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, or tert-butyl.

10. The preparation method according to claim 6, characterized in that, The molar ratio of the alkyllithium to the ligand having the V structure is (1-1.2):1; the molar ratio of the rare earth halide to the ligand having the V structure is (1-1.2):1; and the molar ratio of the substituent compound to the ligand having the V structure is (2-2.4):1.

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