间规聚苯乙烯催化剂研究进展

间规聚苯乙烯是一种高熔点的高分子材料,具有多方面优异特性,在多个领域有广泛的应用前景。综述用于苯乙烯间规聚合的单中心过渡金属催化剂的研究进展,总结各类催化剂用于聚合的特点。简单的单茂钛催化剂(Cp’Ti X3)是最早用于有效催化苯乙烯间规聚合的催化剂,但活性和间规聚合物含量都有待提高;结构如Cp’Ti Xn L的单茂钛催化剂,通过引进非茂给电子配体,可以大大提高聚合活性,提高间规聚合物比例,某些催化剂还可以实现活性聚合;ⅢB过渡金属(钪和稀土元素)化合物作为间规聚苯乙烯聚合催化剂的研究,有助于理解苯乙烯间规聚合,乃至烯烃配位聚合机理。对间规聚苯乙烯催化剂工业现状和研发需求进行分析。     

Syndiotactic polymerization of styrene: Study of catalyst components and polymerization conditions

Syndiotactic polystyrene (s‐PS) was prepared using monotitanocene catalyst of cyclopentadienyl titanium trichloride (CpTiCl₃) activated by methylaluminoxane (MAO). Solution polymerization was carried out in toluene using different polymerization conditions. Syndiotacticity index (SI) between 68 and 91.6% was obtained. Increasing Al/Ti molar ratio shows an increase in both conversion percentage and SI. The conversion increased linearly with increasing Al/Ti molar ratio in the range studied. The conversion reached to an optimum value of about 65% at styrene/Al molar ratio of 2.83, while no regular behavior of SI was observed with changing the ratio. Effect of temperature of the range 50–80°C on polymerization was studied. The most favorable temperature for the polymerization regarding activity is 70°C; however SI decreased with temperature up to 80°C. H₂ value to 140 mL/100 mL solvent increased the productivity of the catalyst, however further increase of H₂ reduced the activity of the catalyst. Polymerization time of 15 to 125 min shows a decrease in activity. The decrease was sharper for about 30 min of polymerization than longer time. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2216–2221, 2006     

A kinetic study of novel bimetallic titanocene catalyst for syndiospecific styrene polymerization

A kinetic study of a syndiospecific polymerization was performed with two kinds of catalysts: Cp*Ti(O(C₆H₄)CMe₂(C₆H₄)O)TiCp* [bimetallic system] and Cp*Ti(OMe)₃ [monometallic system]. The purpose of this study was to determine the reasons behind the high activity of a bimetallic catalyst system. The active site structures of the two kinds of catalysts appears to be similar to the cationic Ti [III] species having η⁵‐pentamethylcyclopentadienyl ligand, while the rate of the activation process of the bimetallic catalyst was found to be higher than that of the monometallic catalyst. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Syndiospecific styrene polymerization with CpTiCl3/MAO: Effects of the order of reactant addition on polymerization and polymer properties

Syndiospecific styrene (St) polymerization, catalyzed by the CpTiCl₃/methylaluminoxane (MAO) system, was investigated using two different activation procedures. The polymerization parameters included polymerization time, temperature (～25–100°C), ratio of [Al]/[Ti] (～100–1000), and catalyst precursor concentration (～0.5–10.0 × 10^?4 mol Ti/L). It was found that adding reactants in the order of (CpTiCl₃ + MAO) + St (Injection of Styrene mode) gave much higher monomer conversion rates, higher weight‐average molecular weights, and narrower molecular weight distributions than for the (St + MAO) + CpTiCl₃ (Injection of Catalyst mode). The former also yielded significantly higher syndiotacticity fractions. Differential scanning calorimetry measurements showed multiple peaks exhibiting polymorphism in crystalline syndiotactic polystyrene samples. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1449–1455, 2004     

Synthesis and characterization of polybutadiene with monotitanocene/methylaluminoxane catalyst

Butadiene was polymerized using a monotitanocene complex of η⁵‐pentamethylcyclopentadienyltribenzyloxy titanium [Cp*Ti(OBz)₃] in the presence of four types of modified methylaluminoxanes (mMAO), which contained different amounts of residual trimethylaluminum (TMA). The titanium oxidation states in Cp*Ti(OBz)₃/mMAO and Cp*Ti(OBz)₃/mMAO/triisobutylaluminum (TIBA) catalytic systems were determined by redox titration method. The effects of various oxidation states of titanium active species on butadiene polymerization were investigated. It was found that Ti(III) active species is more effective for preparing polybutadiene with high molecular weight. The addition of TIBA to the Cp*Ti(OBz)₃/mMAO system could reduce a greater number of Ti(IV) complexes to Ti(III) species and lead to significant increases of polymerization activity and molecular weight of polymer, whereas the polybutadiene microstructure was only slightly changed. On the basis of microstructure and property characterization by FTIR, ¹³C‐NMR, DSC, and WAXD, all resultant polymers were proved to be amorphous polybutadiene with mixed 1,2; cis‐1,4; and trans‐1,4 structures. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2494–2500, 2004     

Effects of residual and external alkylaluminum on the synthesis of syndiotactic polystyrene with cyclopentadienyltitanium tribenzyloxide–methylaluminoxane catalyst

The effects of residual trimethylaluminum (TMA) in methylaluminoxane (MAO) and external alkylaluminum (AlR₃) on styrene syndiotactic polymerization with CpTi(OBz)₃ as a catalyst precursor have been investigated by comparison of the polymerizations using a series of MAOs containing various amounts of residual TMA. The results indicated that the residual TMA plays a deciding role in the reduction of Ti and promotes formation of the active centers for styrene polymerization. The variations in the catalytic activity and molecular weight of the polymer caused by additions of external AlR₃, AlMe₃, AlEt₃, Al(i-Bu)₃, and AlEt₂Cl, into the catalyst systems are quite different, depending the properties of MAO used and the type of the external AlR₃. It was found that there is an optimum range of concentration ratio of the free AlR₃, including the residual TMA and external AlR₃, to the total Al compounds, 25–35 mol %, for maximum catalytic activities. The catalytic activities decrease at the ratios either above or below the range. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 765–770, 1998     

Syndiospecific polymerization of styrene based on dichlorobis(1,3‐diketonato)titanium/methylaluminoxane catalyst system: effects of substituents on catalyst activity

Dichlorobis(substituted‐1,3‐diketonato)titanium complexes 4a–e have been synthesized and were combined with methylaluminoxane as cocatalyst to be employed in the polymerization of styrene. The polystyrenes produced have high syndiotacticities of 94.0–98.2%. The substituents at either 2‐ or 1,3‐positions of 1,3‐diketones can noticeably influence catalyst activities. The catalytic activities of 4a–c bearing 2‐substituents and 4e bearing 1,3‐diphenyl groups are tenfold higher than that of 4d bearing 1,3‐dimethyl groups. The effects of polymerization conditions on the catalyst activities and the syndiotacticities of the polystyrene produced have been examined. © 2000 Society of Chemical Industry     

Preparation of syndiotactic polystyrene/montmorillonite nanocomposites via in situ intercalative polymerization of styrene with monotitanocene catalyst

Syndiotactic polystyrene (sPS)/montmorillonite nanocomposites were prepared via in situ intercalative coordination polymerization using mono‐(η⁵‐pentamethylcyclopenta‐ dienyl) tribenzyloxy titanium [Cp*Ti(OBz)₃] complex activated by methylaluminoxanes (MAO) and triisobutylaluminum (TIBA). The influences of polymerization conditions, such as the weight ratio of montmorillonite and styrene, temperature, and monomer concentration, on the preparation of sPS/montmorillonite nanocomposites was investigated. The intercalation spacing in the nanocomposites, as well as the exfoliation of the montmorillonite interlayers, was characterized with wide angle X‐ray diffraction (WAXD) and transmission electron microscopy (TEM). The dispersibility of the nanoscale elements depended on the polymerization conditions and the surfactant treatment. The crystallizability and thermal properties of these nanocomposites were determined by differential scanning calorimetry (DSC) analysis and thermogravimetric analysis (TGA). Experimental results indicated that the degree of crystallinity of the sPS nanocomposite increased with increasing montmorillonite content and with higher T_g and thermal decomposition temperature than pure sPS. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1412–1417, 2005     

甲基铝氧烷对稀土催化体系催化异戊二烯聚合的影响

考察了甲基铝氧烷(MAO)作为助催化剂对稀土催化体系催化异戊二烯聚合的影响,结果表明MAO可极大地提高体系的催化活性,获得顺-1,4结构含量95%(质量分数)以上的聚异戊二烯,并且调节n(MAO)/n(Nd)和n(Al)/n(Nd)的值可有效地提高聚合产物的相对分子质量.     

An activated neodymium‐based catalyst for styrene polymerization

Coordination polymerization of styrene with a ternary catalyst system composed of catalyst neodymium tricarboxylate (Nd), co‐catalyst Al(i‐Bu)₃ (Al) and chlorinating agent trichloroethane (Cl) was carried out in cyclohexane. The effects of the catalyst system preparation procedure and of the reaction conditions on catalytic activity, molecular weight and molecular weight distribution of the resultant polymers were investigated. The catalytic activity depended mainly on the molar ratios of Al/Nd and of Cl/Nd and on the ageing temperature and polymerization temperature. High polymerization conversion and high catalytic activity could be obtained at high Al/Nd ratios and/or at high ageing temperature. The catalyst system exhibited high activity of 8.32 × 10⁴ g polystyrene (mol Nd h)^?1 at 50 °C. The molecular weight of the polymers obtained reached high weight‐average (M_w) values (M_w = 4.35 × 10⁵ g mol^?1) when Al/Nd = 8, but relatively low values (6000–11 000 g mol^?1) at high Al/Nd ratios. Copyright © 2005 Society of Chemical Industry     

Synthesis and characterization of elastoplastic poly(styrene‐co‐ethylene) using novel mono(η5‐cyclopentadienyl) titanium and modified methylaluminoxane catalysts

Elastoplastic poly(styrene‐co‐ethylene) with high molecular weight was synthesized using novel mono(η⁵‐pentamethylcyclopentadienyl)tribenzyloxy titanium [Cp*Ti(OBz)₃] complex activated with four types of modified methylaluminoxanes (mMAO) containing different amounts of residual trimethylaluminum (TMA). The ideal mMAO, used as a cocatalyst for the copolymerization of styrene with ethylene, contains TMA approaching to 17.8 wt %. The oxidation states of the titanium‐active species in different Cp*Ti(OBz)₃/mMAO catalytic systems were determined by the redox titration method. The results show that both active species may exist in the current system, where one [Ti(IV)] gives a copolymer of styrene and ethylene, and the second one [Ti(III)] only produces syndiotactic polystyrene (sPS). Catalytic activity, compositions of copolymerization products, styrene incorporation, and copolymer microstructure depend on copolymerization conditions, including polymerization temperature, Al/Ti, molar ratio, and comonomers feed ratio. The copolymerization products were fractionated by successive solvent extractions with boiling butanone and tetrahydrofuran (THF). The copolymer, chiefly existing in THF‐soluble fractions, was confirmed by ¹³C‐NMR, GPC, DSC, and WAXD to be an elastoplastic copolymer with a single glass transition temperature. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1851–1857, 1999     

Rate and molecular weight distribution modeling of syndiospecific styrene polymerization over silica-supported metallocene catalyst

The kinetics of syndiospecific polymerization of styrene over silica-supported Cp^∗Ti(OCH₃)₃/MAO catalyst has been investigated through experimentation and theoretical modeling. At low monomer concentrations, the polymerization rate increases almost linearly with monomer conversion, but the reaction rate becomes independent of monomer concentration at high bulk phase monomer concentrations. A kinetic model that incorporates the monomer partition effect between the solid and the liquid phases has been proposed. The model simulations show that the observed non-linear kinetics can be adequately modeled by the monomer partition model. The polymer molecular weight has also been found to increase with the monomer concentration and the polymer molecular weight distribution (MWD) is quite broad, suggesting that the catalytic behavior deviates from the single site catalytic polymerization model. The MWD broadening is modeled by a two-site kinetic model and a good agreement between the model and the experimental data has been obtained.     

苯乙烯间规空间定向聚合

综述国外近年来苯乙烯间规定向聚合的进展,包括高活性催化剂和聚合规律的研究;介绍间规聚苯乙烯(s-PS)主要特性、应用和结构表征情况。     

Preliminary investigations on polymerization catalysts composed of lanthanocene and methylaluminoxane

Summary The polymerization of butadiene(Bd), isoprene(Ip) and styrene(St) has been examined using the six catalyst systems composed of lanthanocene, (C₅H₉Cp)₂NdCl(I), (C₅H₉Cp)₂SmCl(II), (MeCp)₂Sm OAr'(III), (Ind)₂NdCl(IV), Me₂Si(Ind)₂NdCl(V) and (Flu)₂NdCl(VI), and methylaluminoxane(MAO) respectively. All of them can be used to form the polyisoprene with molecular weights of 1 to 10 thousand and cis-1,4-unit contents of 41 to 47%. (I), (II) and (III) of them can be also used to form the polybutadiene with molecular weights of 10 to 20 thousand and cis-1,4-unit contents of 62 to 78%. In addition, the catalysts from (II) to (V) are still active for St polymerization and (II) of them gives a syndio -rich random polystyrene. It is noteworthy that (II) and (III) are active for homopolymerization of Bd, Ip and St in the same polymerization condition. Received: 16 December 1997/Revised version: 17 March 1998/Accepted: 24 March 1998     

Syndiotactic-specific polymerization of styrene: catalyst structure and polymerization mechanism

The mechanistic investigation of syndiotactic-specific polymerization of styrene is reviewed, mainly with reference to the research work carried out at the University of Salerno. NMR analysis of the stereochemical structure of s-PS macromolecules, in some cases suitably labelled, provided valuable information concerning the regiochemistry of polyinsertion, the type of addition to the monomer double bond, and the model of stereospecific propagation. Kinetic studies and spectroscopic investigation of the catalytic systems suggested a cationic Ti(III) complex with a strongly π-co-ordinated benzyl-type growing chain as the true active species. This revised version was published online in June 2006 with corrections to the Cover Date.     

Kinetics of slurry phase polymerization of styrene to syndiotactic polystyrene with pentamethyl cyclopentadienyl titanium trimethoxide and methyl aluminoxane. I. Reaction rate analysis

The kinetics of syndiospecific slurry polymerization of styrene in heptane has been investigated with pentamethyl cyclopentadienyl titanium trimethoxide [Cp??Ti(OMe)₃] catalyst with methylalmuninoxane. The experimental studies at different styrene/heptane ratios indicate that no global gelation occurs at low styrene/heptane ratios even at high styrene conversion. The effective propagation rate constant tends to decrease as polymerization rate is increased at higher initial styrene concentrations. To analyze the effect of catalyst deactivation, a novel three‐stage polymerization experiment has been designed and carried out where monomer is added during the polymerization. The experimental results show that the catalyst activity is very high at the beginning of polymerization but it decreases significantly as catalyst sites are occluded in the solid phase. We also observe that the catalyst remains active for more than 3 h and the rate decay is not solely due to intrinsic catalyst deactivation. Our experimental data suggests that physical transport effects cause the decay in the polymerization rate. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2132–2137, 2003     

Polymerization of styrene using pyrazolylimine nickel (II)/methylaluminoxane catalytic systems

The polymerization of styrene with two pyrazolylimine nickel (II) complexes of (2-(C₃HN₂Me₂-3, 5)(C(Ph) = N(4-R₂C₆H₂(R₁)₂-2, 6)NiBr₂ (Complex 1 , R₁ = ⁱPr, R₂ = H; Complex 2 , R₁ = H, R₂ = NO₂)) activated by methylaluminoxane was studied. The influences of polymerization parameters such as polymerization temperature, Al/Ni molar ratio, and reaction time on catalytic activity and molecular weight of the polystyrene (PS) were investigated in detail. The electron-withdrawing of nitro group in Complex 2 could not enhance the catalytic activity for styrene polymerization; however, the molecular weights of polymers were increased. Both of the two catalytic systems exhibited high activity [up to 8.45 × 10⁵ gPS/(mol Ni h)] for styrene polymerization and provide PS with moderate to low-molecular weights (M_w = 2.21 × 10⁴∼ 5.71 × 10³ g/mol) and narrower molecular weight distributions about 2.0. The obtained PS were characterized by means of IR, ¹H NMR, and ¹³C NMR techniques. The results indicated that the PS was atactic polymer. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Polymerization of styrene using novel bispyrazolylimine dinickel (II)/methylaluminoxane catalytic systems

The polymerization of styrene with a series of bispyrazolylimine dinickel (II) complexes of bis‐2‐(C₃HN₂(R₁)₂‐3,5)(C(R₂) = N(C₆H₃(CH₃)₂‐2,6)Ni₂Br₄ (complex 1 : R₁ = CH₃, R₂ = Ph; complex 2 : R₁ = CH₃, R₂ = 2,4,6‐trimethylphenyl; complex 3 : R₁ = R₂ = Ph; complex 4 : R₁ = Ph, R₂ = 2,4,6‐trimethylphenyl) in the presence of methylaluminoxane (MAO) was studied. The influences of polymerization parameters such as polymerization temperature, Al/Ni molar ratio, reaction time, and catalyst concentration on catalytic activity and molecular weight of the polystyrene were investigated in detail. The influence of the bulkiness of the substituents on polymerization activity was also studied. All of the four catalytic systems exhibited high activity (up to 10.50 × 10⁵ gPS/(mol Ni h)) for styrene polymerization and provide polystyrene with moderate to low molecular weights (M_w = 4.76 × 10⁴–0.71 × 10⁴ g/mol) and narrower molecular weight distributions about 2. The obtained polystyrene was characterized by means of FTIR, ¹H‐NMR, and ¹³C‐NMR techniques. The results indicated that the polystyrene was atactic polymer. The analysis of the end groups of polystyrene indicated that styrene polymerization with bispyrazolylimine dinickel complexes/MAO catalytic systems proceeded through a coordination mechanism. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

酸性膦酸酯钕盐催化丁二烯在苯乙烯溶剂中的选择性聚合

以酸性膦酸酯钕盐Nd(P507)3(简称Nd)、氢化二异丁基铝(简称Al)和倍半乙基铝(简称Cl)为催化剂体系,研究了丁二烯在苯乙烯溶剂中的选择性聚合,考察了溶剂种类、Al/Nd、Cl/Nd及温度对聚合的影响。结果表明,该催化剂体系可在苯乙烯溶剂中实现丁二烯的选择性聚合,在Al/Nd(摩尔比)为10、Cl/Nd(摩尔比)为2.0及聚合温度为50℃的条件下,丁二烯的转化率可达90%以上;聚合物中苯乙烯链节的摩尔分数在4%以下,丁二烯链节的顺式-1,4-结构摩尔分数为90%左右,1,2-结构摩尔分数为4%左右。     

Effect of additives and solvents on polymerization of styrene using CuCl2 + AlEt2Cl catalyst system

The effect of additives and solvents is reported on the rate of polymerization of styrene by the catalyst system (CuCl₂ + AlEt₂Cl). The electron donating additives triphenylphosphine, anisole and diphenyl ether decreases the rate but hydroquinone has no effect on the rate. Increasing dielectric constant of solvents decreases the percentage conversion but chlorinated hydrocarbons do not obey the trend.