Laboratory study of LiOH in inhibiting alkali-silica reaction at 20 °C: a contribution

At 20 °C, alkali-aggregate reaction (AAR) expansion of mortar incorporated zeolitization perlite could be long-term effectively inhibited by LiOH and the effect increased with the augment of Li/(Na+K) molar ratio. Mortar strength would decrease when LiOH was added. The more LiOH was added, the more the strength would decrease. In addition, there was more effect on 28 days' strength than 3 days', and the influence degree of LiOH to compressive strength was higher than that to flexural one. The initial and final setting times of cement were shortened when LiOH was added, and the more Li/(Na+K) molar ratio of LiOH was added, the more the setting time was cut down. Not only mortar bar expansion, the change in 20 °C, but also, the evidence of reaction and the composition of reaction products after 4-year curing was studied by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). It was found that when both Li⁺ and K⁺ (Na⁺) were added, more Li⁺ reacted to form some matter that not as the same as normal alkali-silica reaction (ASR) gel, especially for its nonexpansive property. Such might be the main reason of the phenomenon that ASR expansion could be inhibited by adding lithium compounds.     

Alteration of alkali reactive aggregates autoclaved in different alkali solutions and application to alkali-aggregate reaction in concrete: (I) Alteration of alkali reactive aggregates in alkali solutions

Surface alteration of typical aggregates with alkali-silica reactivity and alkali-carbonate reactivity, i.e. Spratt limestone (SL) and Pittsburg dolomitic limestone (PL), were studied by XRD and SEM/EDS after autoclaving in KOH, NaOH and LiOH solutions at 150 °C for 150 h. The results indicate that: (1) NaOH shows the strongest attack on both ASR and ACR aggregates, the weakest attack is with LiOH. For both aggregates autoclaved in different alkali media, the crystalline degree, morphology and distribution of products are quite different. More crystalline products are formed on rock surfaces in KOH than that in NaOH solution, while almost no amorphous product is formed in LiOH solution; (2) in addition to dedolomitization of PL in KOH, NaOH and LiOH solutions, cryptocrystalline quartz in PL involves in reaction with alkaline solution and forms typical alkali-silica product in NaOH and KOH solutions, but forms lithium silicate (Li₂SiO₃) in LiOH solution; (3) in addition to massive alkali-silica product formed in SL autoclaved in different alkaline solutions, a small amount of dolomite existing in SL may simultaneously dedolomitize and possibly contribute to expansion; (4) it is promising to use the duplex effect of LiOH on ASR and ACR to distinguish the alkali-silica reactivity and alkali-carbonate reactivity of aggregate when both ASR and ACR might coexist.     

The behavior of silicocarbonatite aggregates from the Montreal area

In a previous paper, it was concluded that silicocarbonatite aggregates from the Francon quarry, Montreal contributed to durability problems in Portland cement concrete. Results show that, at 2 days after casting, concrete made with silicocarbonatite aggregates contained over 1.5% more Na₂O than similar bars made with Exshaw limestone aggregates. A reaction involving the rare mineral dawsonite in the silicocarbonatite is thought responsible for the higher Na₂O content. In turn, this caused increased expansion of concrete bars made with alkali expansive aggregates. Also, concrete made with alkali-carbonate reactive Pittsburg aggregate showed more expansion when cured at 80 °C than bars cured at 23 °C. Concrete bars made with Exshaw limestone aggregates cured for 4 h at 85 °C showed late-stage expansion, which is attributed to delayed ettringite formation (DEF). However, no expansion was shown by heat-cured concrete prisms or mortar bars made with silicocarbonatite aggregates. Release of alkalis, aluminates and carbonates by the dawsonite reaction may have inhibited DEF. Concrete bars made with nonreactive Nelson dolostone and 10% silicocarbonatite cured at 80 °C for 4 h showed up to 0.15% expansion after several years at 23 °C and 100% relative humidity (R.H.), indicating that a deleterious reaction did occur.     

Dedolomitization in different alkaline media: Application to Portland cement paste

The dedolomitization reaction kinetics is studied through several long-term experiments consisting of an aqueous dispersion of fine powders of dolomite and portlandite with alkalinity between 0.1 and 1 M KOH, at 25 and 75 °C. The experimental results are numerically simulated to calculate the apparent dissolution constant rates for dolomite, k_dol. At low temperature, two dissolution stages were observed. In an early stage, part of dolomite powder dissolves quickly until an apparent steady is reached. After several days, the reaction continues at a lower rate. The calculated dissolution rate for dolomite in the first stage is one order of magnitude higher than that of the second stage. At 75 °C, the k_dol is two orders of magnitude higher than at 25 °C. The addition of alkali increases the k_dol at high temperature, but reduces it at room temperature.     

Chain transfer reactions limit the molecular weight of polyglycidol prepared via alkali metal based initiating systems

Anionic polymerization of EEGE with alkali metal based initiators has been shown to yield polyglycidol with low polydispersity indices for molecular weights up to M_n ≈ 30,000. Higher molecular weights have not been obtained due to the occurrence of a chain transfer reaction to the monomer. Chain transfer to the monomer leads to P(EEGE) with an alcohol end group and an allylic alcoholate, which reinitiates the polymerization of EEGE. In the present study, the influence of temperature (in a range from 20 °C to 120 °C) and of different initiating systems, such as 3-phenylpropanol/potassium 3-phenylpropanolate, potassium tert-butoxide and sec-butyllithium/phosphazene base, on the chain transfer reaction is investigated. In all cases, the basicity of the alkoxide at the propagating chain end induces chain transfer. The formation of allylic end groups was evidenced by ¹H NMR spectroscopy.     

Synthesis of well-defined block copolymers of n-hexyl isocyanate with isoprene by living anionic polymerization

n-Hexyl isocyanate (HIC) was polymerized at different reaction temperatures and times, using alkali metal naphthalenide, via anionic polymerization in THF. To prevent the formation of trimers, the polymerization of HIC was also performed utilizing sodium tetraphenylborate (NaBPh₄) as a common ion salt. As the reaction temperature decreases, yield of the polymer increases due to stabilization of the active amidate anion at low temperature. In the absence of the additive, a quantitative yield was obtained at −98 °C. However, after most of the monomer was polymerized, further reaction led to trimerization. This was prevented in the presence of NaBPh₄ effectively and the living polymerization was performed successfully at −98 °C. The reaction rate retarded with increasing concentration of NaBPh₄, the optimum concentration of NaBPh₄ was 10 times the concentration of the initiator for the living polymerization of HIC. The living system led to the polymers of molecular weight (MW) as high as 50,000 g/mol. The observed MW was well in agreement with the calculated one. At the higher reaction temperature, −78 °C, the quantitative yield was obtained at 2 min of the reaction time, however the living character was not observed at longer reaction time. The study indicated that the amidate anion was stabilized using NaBPh₄ having bulky contact ion pair. The block copolymer of HIC with isoprene, poly(HIC-b-isoprene-b-HIC), was synthesized with help of the living character of polyisoprene and NaBPh₄. The morphology and composition of the block copolymers were investigated using TEM and ¹H NMR, respectively.     

Cosurfactant effects on the polymerization of vinyl acetate in anionic microemulsion media

The polymerization of vinyl acetate at 60 °C in microemulsions stabilized with the anionic surfactant, Aerosol OT, with or without cosurfactant (n-butanol) is examined. Partial phase diagrams at 60 °C show that the addition of n-butanol enhances the one-phase microemulsion region. Results indicate that the reaction rate is not affected by the presence of the alcohol. However, average molar masses are smaller although particles are bigger throughout the reaction compared to those values obtained in the absence of n-butanol. An explanation for these results is presented.     

Alkali mass balance during the accelerated concrete prism test for alkali-aggregate reactivity

The alkali mass balance was calculated in concrete specimens submitted to the storage conditions of the Canadian standard CSA A23.2-14A concrete prism test for expansion due to alkali-aggregate reaction (AAR). The alkali concentration of both the concrete pore solution expressed under high pressure and the water below specimens in storage pails (bottom water) was measured. Measurements were conducted over a 1-year period, which corresponds to the length of the above test. Two reactive aggregates were tested [Potsdam sandstone (PO) and Spratt limestone (SP)]. Each aggregate was incorporated in two concrete mixtures (mass concrete and structural concrete), for a total of four batches. Significant alkali leaching occurred at 38 °C while performing tests in high moisture storage conditions even though prisms were covered with plastic sleeves. After 52 weeks, the alkali loss ranged from 12% to 25% of the original Na₂O_e content of the concrete, depending on the mixture proportioning and the aggregate type. After estimation of the proportion of alkalis fixed in cement hydrates, it appears that about 23% to 39% of the original alkalis released by the cement are quickly sorbed on aggregate surfaces or have rapidly migrated inside aggregate particles, which may have been incorporated with time in the AAR product. After 52 weeks at 38 °C, the pore solution alkalinity expressed from mass concrete made with PO was 250 mmol/l, whereas the alkalinity was 270 mmol/l in mass concrete incorporating SP. Since prisms of both mixtures were still expanding at 1 year, these alkalinity values are above the thresholds required for sustaining AAR in these concrete mixtures.     

Light scattering study on the dynamic behaviour of cellulose inclusion complex in LiOH/urea aqueous solution

In our previous study, the rapid dissolution of cellulose in alkali/urea aqueous solution at low temperature induced by a dynamic self-assembly process has been demonstrated [1]. The cellulose solution was meta-stable, and its stability could be influenced by system fluctuations (temperature, concentration or time). In the present work, cellulose dissolved in 4.6wt% LiOH/15.0wt% urea aqueous solution pre-cooled to −12 °C was studied by means of dynamic light scattering (DLS). The results revealed that cellulose existed as single inclusion complexes (ICs) associated with LiOH and urea hydrate which could surround the ICs at their surface. And the ICs were stiff, as revealed by results from transmission electron microscopy (TEM) and light scattering (LS). When there was a system fluctuation, the self-association of cellulose with each other took place, resulted from the destruction of the urea shell, and leading to the aggregation of the ICs. For that reason, the ICs stability could be evaluated by the aggregation behaviour. In our findings, the hydrodynamic radius (R_h,app) for the cellulose dispersion in dilute solution shifted to higher values with an increase of the temperature, the concentration or the storage time, indicating an IC aggregation phenomenon.     

Examination of the effects of LiOH, LiCl, and LiNO3 on alkali-silica reaction

Lithium additives have been shown to reduce expansion associated with alkali-silica reaction (ASR), but the mechanism(s) by which they act have not been understood. The aim of this research is to assess the effectiveness of three lithium additives—LiOH, LiCl, and LiNO₃—at various dosages, with a broader goal of improving the understanding of the means by which lithium acts. The effect of lithium additives on ASR was assessed using mortar bar expansion testing and quantitative elemental analysis to measure changes in concentrations of solution phase species (Si, Na, Ca, and Li) in filtrates obtained at different times from slurries of silica gel and alkali solution. Results from mortar bar tests indicate that each of the lithium additives tested was effective in reducing expansion below an acceptable limit of 0.05% at 56 days. However, different lithium additive threshold dosages ([Li₂O]/[Na₂O_e]) were required to accomplish this reduction in expansion; these were found to be approximately 0.6 for LiOH, 0.8 for LiNO₃, and 0.9 for LiCl. Quantitative elemental analysis indicated that sodium and lithium were both bound in reaction products formed within the silica gel slurry. It is also believed that lithium may have been preferentially bound over sodium in at least one of the reaction products because a greater percent decrease in dissolved lithium than dissolved sodium was observed within the first 24 h. It appears that lithium additives either decreased silica dissolution, or promoted precipitation of silica-rich products (some of which may be nonexpansive), because the dissolved silica concentration decreased with increasing dosage of lithium nitrate or lithium chloride additive.     

Influence of stress restraint on the expansive behaviour of concrete affected by alkali-silica reaction

The primary objective of this study was to ascertain whether the Threshold Alkali Level (TAL) of the concrete aggregates may be taken as a suitable reactivity parameter for the selection of aggregates susceptible of alkali-silica reaction (ASR), even when ASR expansion in concrete develops under restrained conditions. Concrete mixes made with different alkali contents and two natural siliceous aggregates with very different TALs were tested for their expansivity at 38 °C and 100% RH under unrestrained and restrained conditions. Four compressive stress levels over the range from 0.17 to 3.50 N/mm² were applied by using a new appositely designed experimental equipment. The lowest stress (0.17 N/mm²) was selected in order to estimate the expansive pressure developed by the ASR gel under “free” expansion conditions. It was found that, even under restrained conditions, the threshold alkali level proves to be a suitable reactivity parameter for designing concrete mixes that are not susceptible of deleterious ASR expansion. An empirical relationship between expansive pressure, concrete alkali content and aggregate TAL was developed in view of its possible use for ASR diagnosis and/or safety evaluation of concrete structures.     

Hyperbranched polymers from divinylbenzene and 1,3-diisopropenylbenzene through anionic self-condensing vinyl polymerization

Hyperbranched polymers were synthesized using anionic self-condensing vinyl polymerization (ASCVP) by forming ‘inimer’ (initiator within a monomer) in situ from divinylbenzene (DVB) and 1,3-diisopropenylbenzene (DIPB) using anionic initiators in THF at −40 °C. The reaction of equimolar amounts of DVB and nBuLi results in the formation of hyperbranched poly(divinylbenzene) through self-condensing vinyl polymerization (SCVP). The hyperbranched polymers were invariably contaminated with small amount of gel (<15%). No gelation was observed when using DIBP with anionic initiators. The presence of monomer-polymer equilibrium in the SCVP of DIPB restricts the growth of hyperbranched poly(DIPB). The inimer synthesized from DIPB at 35 °C undergoes intermolecular self-condensation to different extent depending on the nature of anionic initiator at −40 °C. The molecular weight of the hyperbranched polymers was higher when DPHLi was used as initiator. A small amount of styrene ([styrene]/[Li⁺]=1) was used to promote the chain growth by inducing cross-over reaction with styrene, and subsequent reaction of styryl anion with isopropenyl groups of inimer/hyperbranched oligomer. The hyperbranched polymers were soluble in organic solvents and exhibited broad molecular weight distribution (2<M_w/M_n<17).     

Mechanistic investigation of 9-bromoanthracene photodimers as initiators in atom transfer radical polymerization

Mechanistic pathways accounting for the lack of control in polymerizations employing photodimers of 9-bromoanthracene as alkyl halide initiators in atom transfer radical polymerization (ATRP) reactions are presented. Converting the aryl bromide on the anthracene moiety into an alkyl bromide via a [4+4] cycloaddition reaction effectively generated the photodimer with two alkyl halide sites, which were investigated as potential initiating sites for the ATRP of styrene and n-butyl acrylate. Polymers synthesized using these photodimers as initiators possessed relatively broad polydispersity index (PDI) values and displayed a non-linear relationship between their number average molecular weights (M_n) and monomer consumption, consistent with slow initiation from the bridgehead alkyl halide. Reactions performed at 80 °C in bulk or THF generated polystyrene with M_n values 3-5 times higher than calculated based on monomer-to-initiator ratios. UV-vis spectrometry of the products demonstrated absorbance bands indicative of polymer-bound anthracene, caused by thermal degradation of the photodimer during the polymerization. When the initiator was introduced last into the reaction mixture in an attempt to suppress photodimer cleavage prior to initiation, PDI values and M_n values were generally lowered with the resulting polymers showing similarly high anthracene content. Composition of polystyrene and poly(n-butyl acrylate) products was also studied as a function of reaction temperature, with decreased anthracene labeling observed at lower temperatures (40 and 60 °C), further validating a model of heat-induced cleavage of the photodimer.     

Study of the influence of processing parameters on the production of carboxymethylchitin

Carboxymethylchitin was prepared at different reaction temperatures and from alkali chitin with different concentrations of alkali. Properties of the product were studied. Alkali chitin were prepared using freshly prepared sodium hydroxide of 45, 50, 55, 60 and 65% (w/w) concentration and carboxymethylated using monochloroacetic acid at controlled (35-40 °C) and uncontrolled (30-80 °C) temperature conditions. Molecular weight, viscosity, degree of deacetylation, etc. of the resultant product, i.e. carboxymethylchitin were determined. It was found that the reaction temperature has a profound influence on the property of the product than alkali concentration. A hygroscopic and completely water-soluble product was formed. Optimum conditions for the production of carboxymethylchitin were found to be 60% NaOH concentration and at 35-40 °C reaction temperature. At these conditions, it was obtained with a molecular weight of 4.11×10⁶ Da, viscosity 1926 cP and degree of deacetylation 45.02%.     

Synthesis and characterisation of hydroxyl end-capped telechelic polymers with poly(methyl methacrylate)-block-poly(n-butyl acrylate) backbones via atom transfer radical polymerisation

Hydroxyl end-capped telechelic polymers with poly(methyl methacrylate)-block-poly(n-butyl acrylate) (PMMA-b-PBA) backbones have been prepared via atom transfer radical polymerisation (ATRP) together with a nucleophilic substitution reaction. A hydroxyl-functionalised PMMA macroinitiator (HO-PMMA-Br) was prepared via ATRP at the optimised reaction temperature (60 °C) using 2-hydroxyethyl 2-bromoisobutyrate as the initiator. The high functionality of the bromo end group in the macroinitiator was confirmed by both ¹H NMR technique and a chain-extension reaction. Electrospray ionisation mass spectrometer proved to be a valuable tool for characterising PMMAs with a bromo end group (PMMA-Br), which provided signals corresponding to the intact polymers although multiply charged polymer chains were observed. The well-defined block copolymers HO-PMMA-b-PBA-Br were obtained by the ATRP of n-butyl acrylate using HO-PMMA-Br as a macroinitiator in a one-pot reaction at 100 °C. The kinetics as well as the dependence of the M_n,SEC and PDIs of the obtained block copolymers on the conversions of n-butyl acrylate in the chain-extension reaction suggested negligible radical termination during the reaction, demonstrating that the well-defined HO-PMMA-b-PBA-Br with a high functionality of bromo end group were obtained. The nucleophilic substitution reaction of a monohydroxyl-functionalised block copolymer HO-PMMA-b-PBA-Br with 5-amino-1-pentanol in dimethyl sulfoxide at room temperature was verified with ¹H and ¹³C NMR techniques, which resulted in a series of telechelic polymers HO-PMMA-b-PBA-OH with a functionality of hydroxyl groups up to 1.7 according to the gradient polymer elution chromatography.     

Synthesis and electrochemical properties of lithium-electroactive surface-stabilized silicon quantum dots

Highly lithium-electroactive Si quantum dots (n-Si), coated with an amorphous carbon layer, were prepared by of butyl-capped Si annealing at 700 or 900 °C. The ordering of the carbon layer structure increased with increasing annealing temperature while the thickness decreased to 1 from 2 nm due to the increased ordering of carbon. n-Si, annealed at 900 °C, had the same particle size (5 nm) as n-Si annealed at 700 °C. In contrast to Si nanocrystals with an average particle size of 30 nm that had a first charge capacity of 225 mAh/g with a very small coulombic efficiency of 4%, n-Si that annealed at 900 °C possessed a first charge capacity of 1257 mAh/g with a significantly enhanced coulombic efficiency of 71%. This improvement was due to the uniform distribution of n-Si with a carbon layer that prohibited n-Si aggregation during cycling.     

Effect of chain-length of n-alkane on solvent-induced crystallization and solvent exchange phenomenon in syndiotactic polystyrene

The effect of molecular size and the vapor pressure of a series of n-alkanes as a solvent on solvent-induced crystallization of amorphous sPS and also the solvent exchange phenomenon in the δ form of syndiotactic polystyrene (sPS) were investigated by means of FT-IR spectroscopy and X-ray diffraction. The crystallization of amorphous sPS was found to be very much influenced by the molecular size and the vapor pressure of the n-alkanes used. At room temperature, n-alkanes with six and seven carbon atoms crystallize the sPS into the δ form, whereas the longer n-alkanes did not induce the crystallization of the amorphous sPS. By increasing the crystallization temperature to 50 °C, the vapor pressure of n-alkanes increases and as a result n-alkanes with eight to ten carbon atoms crystallize the amorphous sPS into the γ form unlike the cases of n-hexane and n-heptane. On further increasing the chain-length of n-alkanes to n-tridecane and n-hexadecane, no crystallization of amorphous sPS was observed even at 50 °C. By keeping the crystallization behavior in mind, we used these n-alkanes to exchange the existing solvent in the δ form of sPS/chloroform complex. n-Alkanes with six and seven carbon atoms easily replace the chloroform enclosed in the crystal lattice at room temperature and the d₀₁₀ lattice spacing was found to increase according to the molecular size of the solvent used in the exchange process. n-Alkanes with eight to ten carbon atoms could also replace the chloroform enclosed in the crystal lattice at room temperature. But in this case the d₀₁₀ lattice spacing was found to be similar or lower than that of the δ form of sPS/chloroform complex and a new reflection was observed 2θ = 6.6°, indicating the formation of the ? form. On the other hand, longer n-alkanes (C13 and C16) did not intrude into the cavities of the δ form at room temperature. By increasing the solvent exchange temperature to 50 °C, the longer n-alkanes (C13 and C16) also replaced the existing chloroform in the δ form and structure transformed to the ? form. In this way, we found that the crystallization and solvent exchange process of sPS using n-alkanes is quite complicated and depends strongly on the chain-length of n-alkane molecule.     

Investigation of the intra-particle sintering kinetics of a mainly agglomerated alumina powder by using surface area reduction

An alumina precursor was prepared by the aluminium sulphate (0.20 M) and excess urea reaction in boiling aqueous solution. The precursor was calcined at 900 °C for 2 h and then δ-Al₂O₃ powder having volumetric agglomeration degree of 80% was obtained. Cylindrical compacts having diameter of 14 mm were prepared under 32 MPa by axial pressing using oleic acid as binder. Each compact was fired isothermally at various temperatures between 950 and 1400 °C. The firing time was changed from zero to 2 h. The fired compacts were examined by scanning electron microscopy (SEM) and nitrogen adsorption techniques. The specific surface areas (S/m² g^− 1) of the samples were calculated using the Brunauer, Emmett, and Teller (BET) procedure. The rate constant (k) and mechanism-characteristic parameter (n) were obtained for different temperatures between 950 °C and 1150 °C from the application of the neck-growth sintering rate (NGRM) model on the surface area reduction data. An Arrhenius equation and the parameter n for the sintering were found in the forms of k = (7.648 × 10⁶ h^− 1) exp (− 186,234 J mol^− 1 / RT) and n = 4.0 × 10^− 7 T³-1.7 × 10^− 3 T² + 2.3 T − 1030.8 respectively. The parameter n changes in the interval 0.61 <  n < 1.34 with rising temperature having maximum at about 1025 °C. Based on the SEM images and NGRM data, the intra-particle sintering was discussed.     

Hydrothermal alteration of sedimentary organic matter in the presence and absence of hydrogen to tar then oil

Hydrothermal alteration (hydrous pyrolysis) experiments, in the absence and presence of H₂ (reductive), were conducted on organic matter from marine and lacustrine sediments. The experiments were carried out at discrete temperatures from 150 °C to 350 °C to assess the yields and compositions of the bitumen (tar) formed and subsequently at higher temperatures the oil generated. The yield of bitumen was observed to increase with increasing temperatures. Under hydrous pyrolysis conditions with hydrogen, the yield increases by an order of magnitude and immature lacustrine organic matter shows the highest yield. Bitumen, the extractable organic matter at temperatures below 250-300 °C, contains mainly polar compounds, an unresolved complex mixture (UCM) of branched and cyclic compounds, with low amounts of saturated hydrocarbons. The polar compounds include n-alkanoic acids, n-alkanedioic acids, n-alkanols, isoprenoid ketones and methyl alkanoates. At temperatures above 300 °C, the bitumens transform into petroleum products with saturated hydrocarbons (n-alkanes and biomarkers) and UCM as the major components (>95% of total yield). The degree of maturation of the generated oil increases with increasing temperature under both pyrolysis conditions to full maturity at >350 °C. Although, the bitumen yield is much higher under conditions with added hydrogen, the maturity of the generated oil is lower than with just hydrous pyrolysis.     

Polymerization of 1,3-butadiene with VO(P204)2 and VO(P507)2 activated by alkylaluminum

The oxovanadium phosphonates (VO(P₂₀₄)₂ and VO(P₅₀₇)₂) activated by various alkylaluminums (AlR₃, R = Et, i-Bu, n-Oct; HAlR₂, R = Et, i-Bu) were examined in butadiene (Bd) polymerization. Both VO(P₂₀₄)₂ and VO(P₅₀₇)₂ showed higher activity than those of classical vanadium-based catalysts (e.g. VOCl₃, V(acac)₃). Among the examined catalysts, the VO(P₂₀₄)₂/Al(Oct)₃ system (I) revealed the highest catalytic activity, giving the poly(Bd) bearing M_n of 3.76 × 10⁴ g/mol, and M_w/M_n ratio of 2.9, when the [Al]/[V] molar ratio was 4.0 at 40 °C. The polymerization rate for I is of the first order with respect to the concentration of monomer. High thermal stability of I was found, since a fairly good catalytic activity was achieved even at 70 °C (polymer yield > 33%); the M_n value and M_w/M_n ratio were independent of polymerization temperature in the range of 40-70 °C. By IR and DSC, the poly(Bd)s obtained had high 1,2-unit content (>65%) with atactic configuration. The 1,2-unit content of the polymers obtained by I was nearly unchanged, regardless of variation of reaction conditions, i.e. [Al]/[V], ageing time, and reaction temperature, indicating the high stability of stereospecificity of the active sites.