Homo- and copolymerizations of ethylene and α-olefins in <Emphasis Type="Italic">n</Emphasis>-hexane catalyzed by Ni(ii)-α-diimine catalyst

Ni(II)-α-diimine catalyst [(2,6-i-Pr)₂C₆H₃-DAB(An)]NiBr₂ plus methylaluminoxane was successfully used in the homopolymerization of ethylene, 1-hexene, and 1-octene and the copolymerization of ethylene with 1-hexene and 1-octene in n-hexane. The polymerization of 1-octene was conducted in a controlled manner with a narrow molecular weight distribution (M _w/M _n = 1.2–1.5) and with the weight-average molecular weight increasing linearly with the monomer conversion. The molecular weights, T _g, T _m, branching degree, and density of the obtained (co)polymers were greatly controlled by ethylene pressure and polymerization temperature. Compared with that of ethylene homopolymer, the branching degree of the copolymers prepared by the copolymerization of ethylene with 1-hexene or 1-octene increased, whereas the molecular weight, density, T _m, and catalyst activity decreased. However, compared with those of the homopolymer of 1-hexene or 1-octene, the copolymer density, T _m, and catalyst activity increased, whereas the branching degree declined.     

Polymerization of olefins and polar monomers catalyzed by bis(imino)Ni(II)/dibutylmagnesium/alkylaluminium halide systems

[Bis(N,N′‐dimesitylimino)acenaphthene]dibromonickel ( 1 ) when activated with diethylaluminium chloride (DEAC) is a very active catalyst for ethylene homopolymerization. The activity (A_E) of 1 /100 DEAC is twenty times greater than that of 1 /100 MAO and of the same order of magnitude as 1 /2000 MAO. In the case of homopolymerization of propylene the highest activity (A_P) was obtained at a ratio of 25/15 for Al_DEAC/Ni. Trialkylaluminium compounds were also found to act as cocatalysts for 1 . The PE synthesized with four different cocatalysts was found by ¹³C NMR to have dissimilar branching distributions. 1 /DEAC shows no activity for the polymerization of proximately substituted polar monomers. The introduction of dibutylmagnesium, (DBM) activates the 1 /DEAC system to copolymerize ethylene and a number of proximately substituted polar monomers. Compared with the 1 /MAO/monomer.AlR₃ catalyst system the former is three times more active for copolymerization of 5‐hexene‐1‐ol or 10‐undecen‐1‐oic acid with ethylene. The activity of copolymerization is 1 /24, 1 /5 and 1 /2 as active as homopolymerization, respectively, in the case of methyl vinyl ketone, vinyl acetate and ?‐caprolactam. In the case of tetrahydrofuran/ethylene, the 1 /MAO catalyst produced copolymers using AlR₃ pretreated THF whereas the 1 /DEAC/DBM catalyst produces homopolyethylene only. No polymerization occurred with an acrylonitrile/ethylene mixture in the presence of 1 /DBM/DEAC catalyst. © 2002 Society of Chemical Industry     

Effect of nano-SiO2 particle size on the formation of LLDPE/SiO2 nanocomposite synthesized via the in situ polymerization with metallocene catalyst

Here, we revealed the effect of particle size of the nanoscale SiO₂ on catalytic and characteristic properties of LLDPE/nano-SiO₂ composites synthesized via the in situ polymerization with a zirconocene/MAO catalyst. In the experiment, SiO₂ (10 and 15 nm) was first impregnated with MAO. Then, copolymerization of ethylene/1-hexene was performed in the presence of nano-SiO₂/MAO to produce LLDPE/nano-SiO₂ composites. It was found that the larger particle exhibited higher polymerization activity due to fewer interactions between SiO₂ and MAO. The larger particle also rendered higher insertion of 1-hexene leading to decreased melting temperature (T_m). There was no significant change in the LLDPE molecular structure by means of ¹³C NMR.     

Titanium precatalysts bearing N-substituted β-amino alcohols for 1-hexene polymerization: The effect of steric crowding

A series of titanium-based non-metallocene precatalysts [2-(2,6-dialkylphenylamino)-1-phenylethoxy TiCl₂ were prepared by reacting lithium salts of the corresponding amino alcohols with TiCl₄(THF)₂. Upon activation with methylaluminoxane (MAO), these precatalysts polymerized 1-hexene in isotactic manner. The catalyst activity and polymer properties depended on the steric features in the ortho positions of the aniline moiety of the ligands. As the bulkiness of the alkyl group in ortho positions of the aniline moiety increased, the catalyst showed better activity with high molecular weight and greater tacticity control. For 1-hexene polymerization, precatalyst 1ATiCl₂ showed activity of 3.05 kg of PH/mol-Ti.h at room temperature and the resulting polyhexene had molecular weight of 403,600 (M_w/M_n=1.40) with 80% isotacticity (mmmm). The dibenzylic titanium complexes 1ATi(CH₂Ph)₂ and 3ATi(CH₂Ph)₂, upon activation with MAO or Ph₃CB(C₆F₅)₄, showed relatively lower activities towards 1-hexene polymerization, yielding polymers of lower molecular weights but with narrow molecular weight distribution.     

Organic Nanoparticles with Polypropyleneoxide Chains as Support for Metallocene Catalysts: Ethylene Homopolymerization and Ethylene/α-olefin Copolymerization

Summary Novel organic nanoparticles functionalized with nucleophilic polypropyleneoxide (PPO) chains on their surfaces for supporting metallocene catalysts in heterogeneous olefin polymerization are presented. The nanoparticles (60–100 nm) were obtained by miniemulsion polymerization of styrene, divinylbenzene and PPO functionalized styrene. It is demonstrated that Me₂Si(2MeBenzlnd)₂ZrCl₂/MAO supported on these nanoparticles is suitable for the homopolymerization of ethylene, resulting in excellent product morphologies and high activities. lt is shown that by varying the MAO/Zr ratios and Zr concentrations the activities and productivities of the catalysts as well as the qualities of the polyethylene products can be tuned. These new supported catalysts are also suitable for the copolymerization of ethylene with several comonomers (1-hexene, 1-octene, 1-decene or norbornene). As the obtained product properties like crystallinity, melting temperature or bulk density match the results of silica supported systems, these organic nanoparticles can be considered as alternative carriers in comparison to the established inorganic ones.     

Syndioselective propylene polymerization: Comparison of Me2C(Cp)(Flu)ZrMe2 with Et(Cp)(Flu)ZrMe2

The kinetics and stereochemical control of propylene polymerization initiated by syndiospecific isopropylidene(1-η⁵-cyclopentadienyl)(1-η⁵-fluorenyl)-dimethylzirconium–methyl aluminoxane (1/MAO) and (1-fluorenyl-2-cyclopentadienylethane)-dimethylzirconium–MAO (2/MAO) were investigated. The influence of MAO concentration and polymerization temperature (T_p) on polymerization kinetics and polypropylene properties, such as molecular weight, molecular weight distribution (MWD), and stereoselectivity, have been studied in detail. The activity of both catalytic systems is very sensitive to the concentration of MAO. The 1/MAO and 2/MAO catalysts record maximum activity when [Al]/[Zr] ratio is around 1300 and 2500, respectively. The activity and the degree of stereochemical control are also sensitive to T_p. The 2/MAO catalyst is much more thermally stable than 1/MAO catalyst; the former shows maximum activity at 80°C, whereas the latter shows maximum activity at 20°C. The cationic active species generated by 2/MAO is not so stereorigid as those by 1/MAO so that 2/MAO catalyst produces sPP of broad MWD (4.43–6.38) and low syndiospecificity at high T_p. When T_p is above 50°C, 2/MAO catalyst produces completely atactic polypropylene. The results of fractionation of sPP samples produced by 1/MAO and 2/MAO demonstrate that 1/MAO catalyst is characterized by uniform active sites, but 2/MAO is characterized by multiple active sites. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 973–983, 1998     

Synthesis of linear low density polyethylene with a nano-sized silica supported Cp2ZrCl2/MAO catalyst

A nano-sized silica supported Cp₂ZrCl₂/MAO catalyst was used to catalyze the copolymerization of ethylene/1-hexene and ethylene/1-octene to produce linear low-density polyethylene (LLDPE) in a batch reactor. Under identical reaction conditions, the nano-sized catalyst exhibited significantly higher polymerization activity, and produced copolymer with greater molecular weight and smaller polydispersity index than a corresponding micro-sized catalyst, which was ascribed to the much lower internal diffusion resistance of the nano-sized catalyst. Copolymer density decreased with the increase of polymerization temperature, probably due to the decrease of reactivity ratio r ₁ and ethylene solubility with increasing temperature. Polymerization activity of the nano-sized catalyst increased rapidly with increasing comonomer concentration. Ethylene/1-octene exhibited higher polymerization activity and had a stronger comonomer effect than ethylene/1-hexene.     

RAFT synthesis of poly(N‐isopropylacrylamide) and poly(methacrylic acid) homopolymers and block copolymers: Kinetics and characterization

Reversible addition‐fragmentation chain transfer (RAFT) polymerization was used successfully to synthesize temperature‐responsive poly(N‐isopropylacrylamide) (PNIPAAm), poly(methacrylic acid) (PMAA), and their temperature‐responsive block copolymers. Detailed RAFT polymerization kinetics of the homopolymers was studied. PNIPAAm and PMAA homopolymerization showed living characteristics that include a linear relationship between M _n and conversion, controlled molecular weights, and relatively narrow molecular weight distribution (PDI < 1.3). Furthermore, the homopolymers can be reactivated to produce block copolymers. The RAFT agent, carboxymethyl dithiobenzoate (CMDB), proved to control molecular weight and PDI. As the RAFT agent concentration increases, molecular weight and PDI decreased. However, CMDB showed evidence of having a relatively low chain transfer constant as well as degradation during polymerization. Solution of the block copolymers in phosphate buffered saline displayed temperature reversible characteristics at a lower critical solution temperature (LCST) transition of 31°C. A 5 wt % solution of the block copolymers form thermoreversible gels by a self‐assembly mechanism above the LCST. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1191–1201, 2006     

Living and block polymerization of α-olefins using a Ni(II)-α-diimine catalyst containing OSiPh2Bu groups

A new siloxy-substituted α-diimine compound and its corresponding Ni(II) complex, {bis[N,N′-(4-tert-butyl-diphenylsiloxy-2,6-dimethylphenyl)imino]acenaphthene}dibromonickel (6), were successfully synthesized and the molecular structure of 6 characterized by X-ray crystallography. The precatalyst 6 activated by methylaluminoxane (MAO) or diethylaluminum chloride (DEAC) was tested in the polymerization of ethylene, showed to be highly active (e.g. 2.2×10⁷ and 1.8×10⁷ g polymer (mol Ni.h.bar)⁻¹, respectively) and led to a branched polyethylene (ca. 35-55 branches/1000 C). The catalyst system 6/methylaluminoxane (MAO) catalyzes, at −11 °C, living polymerization of propylene, to a polypropylene showing a syndiotactic-rich microstructure (P_r=0.74). 1-Hexene was also successfully polymerized via a living process, both at −11 and +16 °C. The ¹³C NMR spectra of the poly(1-hexene)s obtained at room temperature show a microstructure almost exclusively composed by n-butyl and methyl branches, the latter being present in a much higher number. Diblock polypropylene-block-poly(1-hexene) and triblock poly(1-hexene)-block-poly(propylene-ran-1-hexene)-block-poly(1-hexene) copolymers have also been synthesized and characterized by GPC/SEC, DSC and NMR.     

Copolymerization of propene and 1-hexene with isospecific and syndiospecific metallocene catalysts

SUMMARY SUMMARY Copolymerization of propene and 1-hexene has been carried out in toluene at 30°C in the presence of homogeneous methylaluminoxane (MAO)-activated 3 ansa-metallocenes, highly syndiospecific iPr(Cp)(Flu)ZrMe₂ ( 1 ), lower syndiospecific Et(Cp)(Flu)ZrMe₂ ( 2 ), and isospecific rac-(EBTHI)ZrMe₂ ( 3 ), in order to study the role of catalyst stereospecificity on comonomer incorporation. The incorporation of 1-hexene decreases in the following order: highly syndiospecific 1 /MAO catalyst > lower syndiospecific 2 /MAO catalyst > isospecific 3 /MAO catalyst. All copolymer chains contain the comonomer in nearly random distribution. The copolymers produced by 1 /MAO and 3 /MAO catalysts were composed of uniform chains, but that by 2 /MAO was fractionated into many fractions in the solvent extraction. Considerable rate enhancements were recorded in the copolymerization when the feed ratio of 1-hexene to propene is around 0.6 for all catalysts. Received: 16 December 1997/Revised version: 9 February 1998/Accepted: 19 February 1998     

Ethylene polymerization using fluorinated FI Zr-based catalyst

A fluorinated FI Zr-based catalyst of bis[N-(3,5-dicumylsalicylidene)-2′,6′-flouroanilinato]zirconium(IV) dichloride was prepared and used for polymerization of ethylene. It was revealed that ortho-F-substituted phenyl ring on the N electronically plays a key role in the suppression of chain transfer reactions especially β-hydride transfer which resulted in an increase in the molecular weight of the obtained polymer and moderation of the catalyst activity as well. Methylaluminoxane (MAO) and triisobuthylaluminum (TIBA) were used as a cocatalyst and a scavenger, respectively. The catalyst showed the maximum activity at about [Al]:[Zr] = 32000:1 M ratio and further addition of MAO did not affect the activity of the catalyst. Ortho-F not only impressed the activity, but also reduced the [Al]:[Zr] molar ratio needed to reach the highest activity in comparison with the similar non-fluorinated FI catalysts. The highest activity of the prepared catalyst was obtained at 35 °C. At the monomer pressure of 3 bars polyethylene was obtained with the viscosity average molecular weight (M _v) of 1.3 × 10⁶ indicating the dramatic effect of ortho-F substitution on the polymerization mechanism. The polymerization was carried out using different amounts of hydrogen. Neither the activity of the catalyst nor the viscosity average molecular weight (M _v) of the obtained polymer was sensitive to the hydrogen concentration. However, higher amount of hydrogen could slightly increase the activity of the catalyst.     

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.     

Polymerization of styrene using bis(β‐ketoamino)nickel(II)/methylaluminoxane catalytic systems

Styrene (St) was polymerized in toluene solution by using bis(β‐ketoamino)nickel(II) complex as the catalyst precursor and methylaluminoxane (MAO) as the cocatalyst. The polymerization conditions, such as Al : Ni ratio, monomer concentration, reaction temperature, and polymerization time, were studied in detail. Both of the bis(β‐ketoamino)nickel(II)/MAO catalytic systems exhibited higher activity for polymerization of styrene, and polymerization gave moderate molecular weight of polystyrene with relatively narrow molecular weight distribution (M_w/M_n < 1.6). The obtained polymer was confirmed to be atactic polystyrene by analyzing the stereo‐triad distributions mm, mr, and rr of aromatic carbon C¹ in NMR spectrum of the polymer. The mechanism of the polymerization was also discussed and a metal–carbon coordination mechanism was proposed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

New fluorine‐containing bissalicylidenimine–titanium complexes for olefin polymerization

Three new titanium complexes bearing salicylidenimine ligands—bis[(salicylidene)‐2,3,5,6‐tetrafluoroanilinato]titanium(IV) dichloride ( 1 ), bis[(3,5‐di‐tert‐butylsalicylidene)‐2,3,5,6‐tetrafluoroanilinato]titanium(IV) dichloride ( 2 ), and bis[(3,5‐di‐tert‐butylsalicylidene)‐4‐trifluoromethyl‐2,3,5,6‐tetrafluoroanilinato]titanium(IV) dichloride ( 3 )—were synthesized. The catalytic activities of 1 – 3 for ethylene polymerization were studied with poly(methylaluminoxane) (MAO) as a cocatalyst. Complex 1 was inactive in ethylene polymerization. Complex 2 at a molar ratio of cocatalyst to pre catalyst of Al_MAO/Ti = 400–1600 showed very high activity in ethylene polymerization comparable to that of the most efficient metallocene complexes and titanium compounds with phenoxy imine and indolide imine chelating ligands. It gave linear high‐molecular‐weight polyethylene [weight‐average molecular weight (M_w) ≥ 1,700,000. weight‐average molecular weight/number‐average molecular weight (M_w/M_n) = 4–5] with a melting point of 142°C. The ability of the 2 /MAO system to copolymerize ethylene with hexene‐1 in toluene was analyzed. No measurable incorporation of the comonomer was observed at 1:1 and 2:1 hexene‐1/ethylene molar ratios. However, the addition of hexene‐1 had a considerable stabilizing effect on the ethylene consumption rate and lowered the melting point of the resultant polymer to 132°C. The 2 /MAO system exhibited low activity for propylene polymerization in a medium of the liquid monomer. The polymer that formed was high‐molecular‐weight atactic polypropylene (M_w ～ 870,000, M_w/M_n = 9–10) showing elastomeric behavior. The activity of 3 /MAO in ethylene polymerization was approximately 70 times lower than that of the 2 /MAO system. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1040–1049, 2005     

Reverse atom‐transfer radical polymerization of acrylonitrile catalyzed by FeCl3/iminodiacetic acid

FeCl₃ coordinated by iminodiacetic acid (IMA) was Changed used for the first time as the catalyst in azobisisobutyronitrile‐initiated reverse atom‐transfer radical polymerization (ATRP) of acrylonitrile (AN). An FeCl₃ to IMA ratio of 1:2 not only gave the best control of molecular weight and its distribution but also provided a rather rapid reaction rate. The effects of solvents on the polymerization of AN were also investigated. The rate of the polymerization in N,N‐dimethylformamide (DMF) was faster than in propylene carbonate or toluene. The molecular weight of polyacrylonitrile agreed reasonably well with the theoretical molecular weight in DMF. The rate of polymerization increased with increasing polymerization temperature and the apparent activation energy was calculated to be 54.8 kJ mol⁻¹. The reverse ATRP of AN did not show obvious living characteristics with CuCl₂ instead of FeCl₃. Copyright © 2005 Society of Chemical Industry     

Polymerization of ethylene to branched poly(ethylene)s using <Emphasis Type="Italic">ansa</Emphasis>-η<Superscript>5</Superscript>-monofluorenyl cyclohexanolato zirconium(IV) complex/methylaluminoxane

ansa-η⁵-Monofluorenyl cyclohexanolato zirconium complex 3 was shown to be active for the polymerization of ethylene when activated with methylaluminoxane (MAO) at 5 bar. Up to a polymerization temperature of 40 °C, 3/MAO resulted in linear poly(ethylene)s with saturated chain ends. However, at polymerization temperatures of 60, 80, and 100 °C, a mixture of branched poly(ethylene)s, linear α-olefins and long chain alkanes was obtained. The poly(ethylene)s produced at 80 and 100 °C exhibited a bimodal molecular weight distribution indicative of multiple active species. Very high molecular weight (M _v > 5 × 10⁵) linear poly(ethylene)s were obtained using 3/MAO at 25 °C.     

Catalytic Behavior of Bis(Pyrrolide-Imine) and Bis(Phenoxy-Imine) Titanium Complexes for the Copolymerization of Ethylene with Propylene, 1-Hexene,or Norbornene

This contribution reports the catalytic behavior of bis(pyrrolide-imine)Ti complexes 1 and 2 , [2-(RNCH)-C₄H₃N]₂TiCl₂ ( 1 , R = Ph; 2 , R = cyclohexyl), and bis(phenoxy-imine)Ti complex 3 , [2-(Ph-NCH)-3-t Bu-C₆H₃O]₂TiCl₂ for the copolymerization of ethylene with propylene, 1-hexene, or norbornene. An inspection of the X-ray structures of complexes 1–3 suggested that complexes 1 and 2 with pyrrolide-imine ligands would provide more space for olefin polymerization than complex 3 with phenoxy-imine ligands. In addition, DFT calculations also showed that active species derived from complexes 1 and 2 possess higher electrophilicity of the Ti center compared to that from complex 3 . Complexes 1 and 2 on activation with methylalumoxane (MAO) had higher affinity for propylene and 1-hexene and incorporated higher amounts of propylene ( 1 ; 30.5 mol%, 2 ; 23.4 mol%) and 1-hexene ( 1 ; 1.9 mol%, 2 ; 1.7 mol%) than complex 3 (propylene; 4.5 mol%, 1-hexene; 0.4 mol%). The incorporation levels of propylene and 1-hexene displayed by complexes 1 and 2 were lower than those for Cp₂TiCl₂ (propylene; 41.6 mol%, 1-hexene; 5.1 mol%) under identical conditions. In contrast, complexes 1 and 2 exhibited higher incorporation ability for norbornene and produced copolymers with much higher norbornene contents ( 1 ; 32.0 mol%, 2 ; 26.5 mol%) than Cp₂TiCl₂ (1.2 mol%) under the same conditions. Additionally, complex 3 also promoted higher norbornene incorporation (4.3 mol%) than Cp₂TiCl₂ and provided a copolymer with extremely narrow molecular weight distribution (M_w/M_n 1.14). A correlation exists between electrophilicity of the Ti center in active species and norbornene incorporation.     

A Chiral Salen-type Schiff Base Cu<Superscript>2+</Superscript> Complex for the Vinylic-type Polymerization of Norbornene

Abstract  

The chiral Salen-type Schiff base ligand H ₂ L (H ₂ L = (s)-(+)2,2′-bis(2-hydroxy-3-methoxybenzylideneamino)-1,1′-binaphthyl), was selected to obtain the new chiral Cu²⁺ complex CuL (1), which was found to catalyze the polymerization of norbornene (NBE). The complex shows the distinctively distorted geometry from a square-planar reactive center, this feature being suggested to account for the efficient catalysis on the vinylic-type polymerization of NBE, with moderate molecular weights and narrow molecular weight distributions.     

Syntheses of well-defined poly(siloxane)-b-poly(styrene) and poly(norbornene)-b-poly(styrene) block copolymers using functional alkoxyamines

Functional alkoxyamines, 1-[4-(4-lithiobutoxy)phenyl]-1-(2,2,6,6-tetramethylpiperidinyl-N-oxyl)ethane (2) and 1-[4-(2-vinyloxyethoxy)phenyl]-1-(2,2,6,6-tetramethylpiperidinyl-N-oxyl)ethane (3) were prepared, and well-defined poly(hexamethylcyclotrisiloxane)-b-poly(styrene)[poly(D₃)-b-poly(St)] and poly(norbornene)-b-poly(St) [poly(NBE)-b-poly(St)] were prepared using the alkoxyamines. The first step was preparation of poly(D₃) and poly(NBE) macroinitiators, which were obtained by the ring-opening anionic polymerization of D₃ using 2 as an initiator and the ring-opening metathesis polymerization of NBE using 3 as a chain transfer. The radical polymerization of St by the poly(D₃) and poly(NBE) macroinitiators proceeded in the ‘living’ fashion to give well-defined poly(D₃)-b-poly(St) and poly(NBE)-b-poly(St) block copolymers.     

Polymerization of vinyl chloride with butyllithiums and metallocene catalysts

Polymerizations of vinyl chloride (VC) with butyllithium (BuLi) and metallocene catalysts were investigated. In the polymerization of VC with BuLi, the activity for polymerization decreased in the following order; t‐BuLi > n‐BuLi > s‐BuLi. A polymer controlled structurally in the main chain was found to be synthesized from the polymerization of VC with BuLi. The molecular weights of polymers obtained in bulk polymerization were higher than those of polymers obtained in solution. A linear relationship of the M_n of the polymer and the polymer yields was observed. The M_w/M_n of the polymer did not change significantly during polymerization, although the M_w/M_n was around 2. Thermal stability of the polymer obtained with BuLi was higher than that of polymer obtained with radical initiators, as determined by TGA measurements. In the polymerization of VC with Cp*TiX₃/MAO (X: Cl and OCH₃) catalysts, polymers were obtained with both catalysts, although the rate of polymerization was slow. The Cp*Ti(OCH₃)₃//MAO catalyst in CH₂Cl₂ gave higher‐molecular‐weight polymers in a better yield than in toluene. From elemental analysis and the NMR spectra of the polymers, the Cp*Ti(OCH₃)₃/MAO catalyst gave polymers consisting of repeating regular head‐to‐tail units, in contrast to the Cp*TiCl₃/MAO catalyst, which gave polymers having anomalous units.