Methylaluminoxane‐activated neodymium chloride tributylphosphate catalyst for isoprene polymerization

The polymerization of isoprene was examined by using a novel binary catalyst system composed of neodymium chloride tributylphosphate (NdCl₃·3TBP) and methylaluminoxane (MAO). The NdCl₃·3TBP/MAO catalyst worked effectively in a low MAO level ([Al]/[Nd] = 50) to afford polymers with high molecular weight (M_n ～10⁵), narrow molecular weight distribution (M_w/M_n = 1.4–1.6), and high cis‐1,4 stereoregularity (> 96%). The catalytic activity increased with an increasing [Al]/[Nd] ratio from 30 to 100 and polymerization temperature from 0 to 50°C, while the M_n of polymer decreased. The presence of free TBP resulted in low polymer yield. Polymerization solvent remarkably affected the polymerization behaviors; the polymerizations in aliphatic solvents (cyclohexane and hexane) gave polymer in higher yield than that in toluene. The M_w/M_n ratio of the producing polymer remained around 1.5 and the gel permeation chromatographic curve was always unimodal, indicating the presence of a single active site in the polymerization system. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40153.     

Reversible coordinative chain transfer polymerization of isoprene and copolymerization with ε-caprolactone by neodymium-based catalyst

Coordinative chain transfer polymerization (CCTP) of isoprene was investigated by using the typical Ziegler–Natta catalytic system [Nd(Oi-Pr)₃/Al(i-Bu)₂H/Me₂SiCl₂] with Al(i-Bu)₂H as cocatalyst and chain transfer agent (CTA). The catalyst system exhibited high catalytic efficiency for the reversible CCTP of isoprene and yielded 6–8 polymer chains per Nd atom due to the high chain transfer ability of Al(i-Bu)₂H. The narrow molecular weight distribution (M_w/M_n = 1.22–1.45) of the polymers, the good linear relationship between the M_n and yield of the polymer, and the feasible seeding polymerization of isoprene indicated the living natures of the catalyst species. Moreover, the living Nd-polyisoprene active species could further initiate the ring-opening polymerization of polar monomer (ε-caprolactone) to afford an amphiphilic block copolymer consisting of cis-1,4-polyisoprene and poly(ε-caprolactone) with controllable molecular weight and narrow molecular weight distribution.     

Homogeneous neodymium iso-propoxide/modified methylaluminoxane catalyst for isoprene polymerization

The neodymium iso-propoxide [Nd(Oi-Pr)₃] catalyst activated by modified methylaluminoxane (MMAO) is homogeneous and effective in isoprene polymerization in heptane to provide polymers with high molecular weight (M_n∼10⁵), narrow molecular weight distribution (M_w/M_n=1.1-2.0) and mainly cis-1,4 structure (82-93%). The polymer yield increased with increasing [Al]/[Nd] ratio (50-300 mole ratio) and polymerization temperature (0-60 °C), while the molecular weight and cis-1,4 content decreased. On the other hand, the same catalyst resulted in relatively low polymer yield and low molecular weight in toluene. The cyclized polyisoprene was formed in dichloromethane, which is attributable to the cationic active species derived from MMAO alone. When chlorine sources (Et₂AlCl, t-BuCl, Me₃SiCl) were added, the cis-1,4 stereoregularity of polymer improved up to 95% even at a high temperature of 60 °C, though the polymer yield decreased.     

Living polymerization of 1,3-butadiene by a Ziegler-Natta type catalyst composed of iron(III) 2-ethylhexanoate, triisobutylaluminum and diethyl phosphite

Living characteristics of facilely prepared Ziegler-Natta type catalyst system consisting of iron(III) 2-ethylhexanoate, triisobutylaluminum and diethyl phosphite have been found in the polymerization of 1,3-butadiene in hexane at 40 °C. The characteristics have been well demonstrated by: a first-order kinetics with respect to monomer conversion, a narrow molecular weight distribution (M_w/M_n = 1.48-1.52) of polybutadiene in the entire range of polymerization conversion and a good linearity between M_n and the yield of polymer. Feasible post-polymerization of 1,3-butadiene and block co-polymerization of 1,3-butadiene and isoprene further support the living natures of the catalyst bestowed with. The current catalyst system is highly active (yield > 80%, 35 min), providing polybutadiene with 1,2, cis-1,4 and trans-1,4 units about 44.0%, 51.0% and 5.0%, respectively.     

A convenient route to high molecular weight highly isotactic polystyrene using Ziegler-Natta catalysts and ultrasound

Ziegler-Natta (TiCl₄/AlEt₃) catalysts and ultrasound were used to prepare highly isotactic polystyrene (ca. 99%) with a molecular weight of 4.7×10⁶ mol g⁻¹ and low molecular weight distribution (M_w/M_n=1.6) via a convenient method. Ultrasound was most effective if applied only during an initial stage in the polymerisation, most likely permitting dispersion of catalyst particles which were subsequently coated and separated by growing polymer chains. Yields could be improved by varying the amount of catalyst and reaction time.     

Bulk polymerization of vinyl chloride with half-titanocene/MAO catalyst

Bulk polymerization of vinyl chloride (VC) with Cp^∗Ti(OPh)₃/MAO catalyst was investigated. The bulk polymerization of VC with Cp^∗Ti(OPh)₃/MAO catalyst proceeded to give poly(vinyl chloride) (PVC) with high molecular weight in good yields. The M_n of the polymer increased in direct proportion to polymer yields and the line passed through the origin. The M_w/M_n of the polymer decreased with an increase of polymer yield. The GPC elution curves were unimodal and the whole curves shifted clearly to the higher molecular weight as a function of reaction time. This indicates that the control of molecular weight can be achieved in the polymerization of VC with Cp^∗Ti(OPh)₃/MAO catalyst even in bulk. The structure of PVC obtained from the bulk polymerization of VC with Cp^∗Ti(OPh)₃/MAO catalyst consists of a regular structure. The thermal stability of the polymer obtained with Cp^∗Ti(OPh)/MAO catalyst was higher than that of PVC obtained from radical polymerization and depended on the molecular weight of the polymer. In contrast to that, the initial decomposition temperature of the polymer obtained from a radical polymerization did not depend on the molecular weight. We presumed that the decomposition of the polymer obtained with Cp^∗Ti(OPh)₃/MAO catalyst initiated at the chain end.     

Novel Neodymium-Based Ternary Catalyst, Nd(Oi-Pr)3/[HNMe2Ph]+[B(C6F5)4]-/i-Bu3Al, for Isoprene Polymerization

Summary Polymerization of isoprene was investigated by using a novel ternary catalyst system composed of neodymium(III) isopropoxide (Nd(OiPr)₃), dimethylphenylammonium tetrakis(pentafluorophenyl)borate ([HNMe₂Ph]⁺[B(C₆F₅)₄]^-; borate), and triisobutylaluminum (i-Bu₃Al). The mole ratios of borate and aluminum compounds to Nd catalyst significantly affected the polymerization behavior. Both yield and cis-1,4 content of polyisoprene decreased in the case of [borate]/[Nd] < 1.0, while at [borate]/[Nd] > 1.0 the formation of multiple active species resulted in the polymer showing bimodal peaks in GPC. When the [Al]/[Nd] ratio was lower than 30, the polymer yield sharply decreased, whereas the cis-1,4 content became relatively low with use of a large excess of Al ([Al]/[Nd] > 50). Thus, the optimal catalyst composition was [Nd]/[borate]/[Al] = 1/1/30, which gave in > 97% yield polyisoprene with high molecular weight (M_n2×10⁵) and relatively narrow molecular weight distribution (M_w/M_n2.0) and mainly cis-1,4 structure (90%).     

Polymerization of n-Hexyl Isocyanate with Rare Earth Catalyst Composed of Nd(P204)3/Al(i-Bu)3

Summary Rare earth catalyst system: lanthanide phosphonate/tri-i-butyl aluminum (Nd(P₂₀₄)₃/Al(i-Bu)₃) has been found for the first time as a novel catalyst for the polymerization of n-hexyl isocyanate (HNCO). Nd(P₂₀₄)₃ and Nd(P₅₀₇)₃ are the commercial names of neodymium 2-ethylhexyl phosphonates, their formulas are shown in table 1. The catalyst can be prepared easily by mixing Nd(P₂₀₄)₃ and Al(i-Bu)₃. The effects of catalyst, solvent, reaction temperature and time on the polymerization of HNCO were studied. The obtained poly (n-hexyl isocyanate) (PHNCO) was characterized by GPC, FT-IR, ¹H-NMR and TGA. The resulting PHNCO had molecular weight (Mn=39.6×10⁴, Mv=67.2×10⁴), molecular weight distribution (MWD=2.44) and yield (82.7%) under the moderate reaction conditions: catalyst concentration [Nd]=6.65×10^-2mol/L, Al/Nd=10 molar ratio, [HNCO]/[Nd]=100 molar ratio, at -10^oC for 10h in bulk. Relatively high reaction temperature (-10^oC) is the most distinct virtue. The IR and NMR analyses show that the polymer obtained is not polyether but polyisocyanate.     

Stereocontrolled styrene-isoprene copolymerization and styrene-ethylene-isoprene terpolymerization with a single-component allyl ansa-neodymocene catalyst

The ansa-metallocene complex (CpCMe₂Flu)Nd(C₃H₅)(THF) (1) is an effective single-component catalyst for the production of syndiotactic styrene-rich polymer materials modified by isoprene and/or ethylene. The recovered copolymers have high molecular weights (M_n = 12,000-91,000 g/mol) and unimodal, relatively narrow molecular weight distributions (M_w/M_n = 1.3-2.8). The comonomer feeds can be easily manipulated to tune the respective amounts of monomers incorporated in the copolymer and eventually modify the final properties (T_m, T_g) of the obtained materials.     

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     

Kinetic study on propylene polymerization with MgCl2/TiCl4-AlEt3/PhCO2Et System — the role of ethyl benzoate

Summary A kinetic study on propylene polymerization with the catalyst system of MgCl₂-supported TiCl₄ catalyst(MgCl₂/TiCl₄) in conjunction with AlEt₃ and PhCO₂Et (EB) has been made to elucidate the role of ethyl benzoate (EB) which is known to increase stereospecificity of produced polypropylene. It has been found that a part of added EB was fixed on the supported Ti catalyst and that EB modified the isotactic specific centers to increase the k_p (iso) value. Thus the productivity of isotactic polymer and the molecular weight of the isotactic polymer(2·10⁴(¯Mn) to 6·10⁴ at 60°C) were increased.     

Effect of immobilization of titanocene catalyst in aralkyl imidazolium chloroaluminate media on performance of biphasic ethylene polymerization and polyethylene properties

1-(2-Phenylethyl)-3-methylimidazolium and 1-benzyl-3-methylimidazolium chloroaluminates, [Ph-C₂mim][AlCl₄] and [Bzlmim][AlCl₄], were applied as media of the Cp₂TiCl₂ catalyst for biphasic ethylene polymerization. The studied aralkyl ionic liquids ensure greater stability of the catalyst at higher temperatures and more regular morphology of the produced polyethylene than analogous 1-n-alkyl-3-methylimidazolium chloroaluminates. The alkylaluminium compound participates in the termination reaction of the polymer chain. The catalyst is stable and enables recycling of the ionic liquid phase in the consecutive polymerization reactions. The [Ph-C₂mim][AlCl₄] ionic liquid and AlEt₂Cl alkylaluminium compound turned out to be the most suitable for the biphasic process. The influence of the kind of ionic liquid, alkylaluminium compound (AlEt₂Cl and AlEtCl₂), activator/catalyst molar ratio, reaction temperature, reaction time and catalyst recycling on the polymerization performance as well as polyethylene properties such as molecular weight (M _w ), polydispersity, melting temperature, crystallinity degree, bulk density and particle size is presented.     

Morphology and activity of nanosized NdCl3 catalyst for 1,3‐butadiene polymerization

The binary lanthanide catalyst for 1,3‐butadiene was invented for 40 years ago. However, it has not been employed in commercial application due to its poor solubility and low activity. Nanosized neodymium chloride (NdCl₃) was prepared in tetrahydrofuran (THF) medium through dissolution, chelation, and colloidal formation steps. Anhydrous NdCl₃ was dissolved in THF, and ca. 1.5 THF molecules were coordinated. In the colloidal formation step, THF was slowly replaced with the addition of cyclohexane, and pale blue nuclei, nanosize below 200 nm, were formed. The structural studies for NdCl₃ · xTHF using X‐ray powder diffraction (XRD) and scanning electron microscope (SEM) indicate that high ordered crystallinity is decreased with reduced particle size from trigonal prismatic to porous sphere structure. Nano NdCl₃, obtained as colloidal state in cyclohexane, was activated with Al(iBu)₃ and Al(iBu)₂H at room temperature and employed for 1,3‐butadiene solution polymerization. The nanosized Nd catalysts showed high activity (1.0 ～ 1.3 × 10⁵ g/Nd mol · h), which is comparable to that of the ternary neodymium catalyst Nd(neodecanoate)₃/AlEt₂Cl/Al(iBu)₃. The microstructures of polybutadiene, cis, trans, and vinyl, are about 96.0, 3.5, and 0.5%, respectively. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1279–1283, 2005     

Controlled radical polymerization of n-hexadecyl methacrylate mediated by tris(2,2′-bipyridine)iron(III) complexes

Poly(n-hexadecyl methacrylate) (PHMA) with narrow molecular weight distribution has been synthesized by atom transfer radical polymerization (ATRP) and reverse ATRP of n-hexadecyl methacrylate (HMA) at 80 °C in N, N-dimethylformamide (DMF) using the CBr₄/tris(2,2′-bipyridine)iron(III) complex initiation system in the presence of 2,2′-azobisisobutyronitrile (AIBN). From the kinetic studies and molecular weight data, it reveals the controlled nature of polymerization. The effect of various reaction parameters on number-average molecular weight (M _n ) and molecular weight distribution (M _w /M _n ) have been investigated. For the reverse ATRP, the catalyst tris(2,2′-bipyridine)iron(III)complex, [Fe(bpy)₃]³⁺, played an important role in polymerization rate and M _w /M _n . The resulting PHMA that obtained by reverse ATRP shows the best control of molecular weights and its distribution as compared to normal ATRP system. PHMA has been characterized by different techniques such as GPC, XRD and NMR spectroscopy.     

Synthesis of ultra‐high molecular weight polystyrene with rare earth–magnesium alkyl catalyst system: general features of bulk polymerization

Bulk polymerization of styrene (St) with an in‐situ‐activated Ziegler‐catalyst containing neodymium 2‐ethylhexyl phosphonate [Nd(P₂₀₄)₃], magnesium–aluminum alkyls and hexamethyl phosphoramide (HMPA) was studied. The new rare‐earth catalyst exhibited high activity for polymerization of styrene, and its catalytic efficiency reached 14 730 g PSt/g Nd. The influence of reaction parameters, such as Mg/Nd, Mg/Al, St/Nd molar ratios, temperature, etc, on the catalyst performance was examined in detail. The molecular weight of the resulting polystyrene is ultra‐high (M_W = 40 × 10⁴ ∼ 120 × 10⁴ g mol⁻¹) and the distribution of molecular weight is broad (M_W/M_n = 2.1 ∼ 2.8). The microstructure of the polystyrene was characterized by IR and ¹³C NMR spectroscopies and found to be atactic. © 2001 Society of Chemical Industry     

<Emphasis Type="Italic">m</Emphasis>-Cresol-substituted triethyl aluminum/MoCl<Subscript>5</Subscript>/TBP catalytic system for coordination polymerization of butadiene

Coordination polymerization of butadiene was initiated by a catalyst system consisting of tributyl phosphate (TBP) as ligand, molybdenum pentachloride as primary catalyst and triethyl aluminum substituted by m-cresol as co-catalyst. The effects of the substitution of m-cresol on the activity of the catalyst system, molecular weight and molecular weight distribution, intrinsic viscosity and microstructures of the resulting polymers were investigated in details. The molecular weight and molecular weight distribution of the polymerization products were determined by GPC. The microstructure of the polymerization products was characterized by FTIR, ¹³C NMR and DSC techniques. The experimental results indicated that the polymerization activity of the reaction system and the molecular weight of the polymerization products gradually increased with the increase of the substitution content of m-cresol, namely, Al(OPhCH₃)₂Et?>?Al(OPhCH₃)Et₂?>?Al(OPhCH₃)_0.5Et_2.5>AlEt₃. The 1,2-structure contents of the polymerization products could be adjusted between 89 and 91% through the control of the substitution of m-cresol, and there was minute quantities of crystalline structures in the resulting polymers due to the increasing content of the syndiotactic 1,2-polybutadiene. In a word, the existence and increase of steric hindrance of m-cresol made it easier for polymerization products to form interdisciplinary 1,2-structure.     

Polymerization of isoprene in n-heptane with triethylaluminum–titanium tetrachloride catalyst. I. Effect of Al/Ti ratio on stereoregularity,conversion, molecular weight,and molecular weight distribution

The influence of the Al/Ti ratio of the heterogeneous Ziegler–Natta catalyst system AlEt₃–TiCl₄ on the isoprene polymerization in n-heptane at 30°C in a bench scale reactor was investigated. Each batch run consisted of 50 mL isoprene, 200 mL n-heptane with 0.45 and 0.5g catalyst. Conversion of isoprene and molecular weights of polyisoprene increased with increasing Al/Ti ratio, reaching their maxima values at 1.0 and 1.2, respectively. Conversion and molecular weights decreased remarkably at a higher ratio of Al/Ti. As this ratio decreases from the value of 1.2 to 0.4, the cis1,4 content in polyisoprene decreased from 97 to 25%. When the ratio of Al/Ti increased from 1.2 to 2.2 the cis-1,4 structure of polyisoprene decreased from 97 to 85%.     

Synthesis of star polymer by means of the living polymerization of [(o-trifluoromethyl)phenyl]acetylene using a MoOCl4-based catalyst and the linking method

A star polymer was synthesized by addition of 1,4-diethynyl-2,5-dimethylbenzene as linking agent (30 °C, 24 h) after living polymerization of [(o-trifluoromethyl)phenyl]acetylene (o-CF₃PA) with MoOCl₄-n-Bu₄Sn-EtOH catalyst (in anisole, 30 °C, 20 min; [Mo]=10 mM, [P^∗]/[Mo]=40%, [o-CF₃PA]₀=200 mM). The M_n values of the living and star polymers were 8.1×10³ and 5.3×10⁴, respectively, according to gel permeation chromatography, while these values determined by multi-angle laser light scattering (MALLS) were 7.8×10³ and 2.5×10⁵. The M_w/M_n and arm number of the star polymer were 1.04 and 29, respectively, according to MALLS. The molecular weight and arm number of star polymer increased with increasing linking agent concentration and polymerization temperature.     

A single active site metal center of neodymocene chloride for the ring‐opening polymerization of ε‐caprolactone

A germyl‐bridged lanthanocene chloride, Me₂Ge(^tBu‐C₅H₃)₂LnCl (Ln = Nd; (Cat‐ Nd ), was prepared and successfully used as single catalyst to initiate the ring‐opening polymerization of ε‐caprolactone (ε‐CL) for the first time. Under mild conditions (60°C,[ε‐CL]/[Ln] = 200, 4 h), Cat‐ Nd efficiently catalyzes the polymerization of ε‐CL, giving poly(ε‐caprolactone) (PCL) with high molecular weight (MW) (>2.5 × 10⁴) in high yield (>95%). The effects of molar ratio of [ε‐CL]/Cat‐Nd, polymerization temperature and time, as well as solvent were determined in detail. When the polymerization is carried out in bulk or in petroleum ether, it gives PCL with higher MW and perfect conversion (100%). The higher catalytic activity of this neodymocene chloride could be ascribed to the bigger atom in the bridge of bridged ring ligands. Some activators, such as NaBPh₄, KBH₄, AlEt_3, and Al(i‐Bu)₃, can promote the polymerization of ε‐CL by Cat‐ Nd, which leads to an increase both in the polymerization conversion and in the MW of PCL. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci 123: 1212–1217, 2012     

Polymerization of vinyl ethers using titanium catalysts containing tridentate triamine ligand of the type N[CH2CH(Ph)(Ts)N]2

Titanium complexes having tridentate triamine of the type N[CH₂CH(Ph)(Ts)N]₂²⁻ in combination with methylaluminoxane (MAO) was able to polymerize ethyl vinyl ether in good yields. The polymers obtained in general were having molecular weight in the order of 10⁵ with narrow molecular weight distributions. Polymerization conditions had an impact on the molecular weight and the polydispersity index (PDI). Using chlorobenzene as the solvent the polymer had an M_n of 350?000 and PDI of 1.21, where as under neat conditions the M_n was 255?000 with PDI of 1.21. The type of solvent and the temperature dictated the polymerization rate and the polymer stereo regularity. The molecular weight of the polymer is distinctly governed by the polymerization temperature. Temperature ranging between −50 and ambient (30 °C) resulted in high molecular weight polymers and vice versa at a temperature of 60-70 °C resulted in low molecular weight polymers in moderate yields. The polymers obtained below 30 °C are highly stereo-regular compared to that of the ones produced at and above ambient temperature. The polymerization of iso-butyl vinyl ether (IBVE) was faster than that of linearly substituted n-butyl vinyl ether (BVE) and less bulky ethyl vinyl ether (EVE). The order of isotacticities of the polymers obtained are polyIBVE > polyBVE > polyEVE. The use of borate cocatalyst for activation generated narrow molecular weight polymers with a linear increase in the yield and molecular weight over time suggesting the living nature of the catalyst system.