Cationic polymerization of α-pinene with the binary catalyst AlCl3/SbCl3

Oligomers of α-pinene ( 1 ) with relatively high molecular weight (number-average molecular weight M _n = 1140, weight-average molecular weight M _w = 2590) were obtained with the binary catalyst AlCl₃/SbCl₃ in toluene at ? 15°C ([AlCl₃]₀ = 42,5 mmol · L^?1, mole ratio SbCl₃/AlCl₃ = 0,50). The yield was higher than 90%, and the dimer content was as low as 5 wt.-%. In contrast, AlCl₃ alone gave predominantly dimers and lower oligomers in poor yield, whereas SbCl₃ had no catalytic activity for 1. ¹H NMR analysis reveled that the structure of the higher-molecular-weight fraction (M _n = 2920, M _w = 3690) of the oligomers obtained with AlCl₃/SbCl₃ is 6 , which consists of a cyclohexene ring with an endo-olefin group, most likely derived from the cationic monomer isomerization of α-pinene via the ring-opening of the cyclobutane unit. Effects of the reaction conditions on the polymerization rate and molecular weight were also investigated.     

Monomer-isomerization polymerization, 37. Effect of transition metal chlorides on monomer-isomerization polymerization of 2-butene with TiCl3/Al(C2H5)3 as catalyst

The effect of transition metal chlorides (MtCl_x) as isomerization catalysts was examined in the monomer-isomerization polymerization of cis-2-butene with TiCl₃/Al(C₂H₅)₃ as a catalyst. The isomerization and polymerization depend on both, MtCl_x and MtCl_x/TiCl₃ mole ratio. The rate of polymerization of 2-butene with TiCl₃/Al(C₂H₅)₃/MtCl_x (mole ratio Al/Ti = 3,0, Mt/Ti = 1,0) as catalysts decreases in the following order: NiCl₂ > CoCl₂ > FeCl₃ > None > MnCl₂ > CrCl₃. This order was found to be in a good agreement with the electronegativity of the metal atom in the chloride.     

Propene polymerization with a Mg(OC2H5)2-supported TiCl4 catalyst, 3. The role of benzoyl chloride

The catalyst systems Mg(OC₂H₅)₂/benzoyl chloride (BC)/TiCl₄ and Mg(OC₂H₅)₂/ethyl benzoate (EB)/TiCl₄ were prepared for the polymerization of propene. In case of the Mg(OC₂H₅)₂/BC/TiCl₄ catalyst, BC changes into the internal donor EB during the in situ preparation of the catalyst and the unchanged BC acts as additional donor after reaction with triethylaluminium (TEA). Catalyst activity and isospecificity were also studied for the two catalysts by changing the amounts of BC or EB in the polymerization of propene cocatalyzed with TEA.     

Kinetics of polymerization of 1,3-dioxepane with the Al(C2H5)3/H2O catalyst system

The kinetics of the polymerization of 1,3-dioxepane (DH) with the catalytic system Al(C₂H₅)₃/H₂O was studied. The dependence of the polymerization rate R₀ of the monomer DH(M) may be represented by the equation: The kinetic scheme which verifies the obtained results is that which takes into consideration in the starting period of the polymerization the existence of chain transfer to the monomer. The decrease of the polymerization rate and the diminishing of the intrinsic viscosity at high conversions points to the existence of chain transfer to the polymer in this stage of the reaction. The reaction rate constants of the chain transfer to the monomer are one order of magnitude higher than those of the transfer reaction to the polymer.     

Influence of ethyl benzoate on copolymerization of styrene and 1-hexene with the titanium-based systems (α)-TiCl3(H) and TiCl3 · 1/3 AlCl3

The influence of ethyl benzoate (E.B.) on the copolymerization of styrene with 1-hexene, initiated by isospecific Ziegler-Natta catalysts α-TiCl₃(H)-AlEt₃ and TiCl₃ · 1/3 AlCl₃-AlEt₃ (mole ratio Al/Ti = 3), was examined. Ethyl benzoate was found to reduce the activity of the catalysts. In addition it leads, depending on the Ti catalyst, to opposite effects on the apparent reactivity order of the two monomers. Incorporation of styrene into the copolymers is reduced when E. B. is added to TiCl₃ · 1/3 AlCl₃-AlEt₃. On the contrary, a much higher incorporation of styrene is observed with α-TiCl₃(H)-AlEt₃ in the presence of E. B. For this system the calculated reactivity ratio varies strongly with increasing proportion of E. B.: for a mole ratio AlEt₃/E. B. = 3, r_S = 0,94 and r_H = 1,46 and for AlEt₃/E. B. = 2, r_S = 8 and r_H = 0,1. Changes in the stereoregularity of copolymers suggest that E. B. leads to an inhibition of the less stereospecific sites for TiCl₃ · 1/3 AlCl₃-AlEt₃, whereas its addition suppresses the stereospecificity of the α-TiCl₃(H)-AlEt₃ catalyst. Contributions of conventional cationic and/or radical processes to the copolymerization reaction were examined and may be ruled out.     

Polymerization of α-olefins in the presence of δ-TiCl3/Al(CH3)3: Chain propagation rate constants for ethylene and propene

The chain propagation rate constants for the polymerization of ethylene and propene in the presence of δ-TiCl₃/Al(CH₃)₃ at 22 °C are determined by means of a ¹³C NMR analysis of suitable block copolymers. The numerical values of the rate constants are compared with those previously reported.     

Cationic polymerization of α-pinene with aluminium-based binary catalysts, 2. Survey of catalyst systems

A series of metal halides (AlCl₃, AlBr₃, AlEtCl₂, BF₃ · OEt₂, SnCl₄, TiCl₄, and WCl₆) were employed in conjunction with antimony trichloride (SbCl₃) for the cationic polymerization of α-pinene in toluene at ?15°C. The combinations of aluminium halides (AlCl₃, AlBr₃, and AlEtCl₂) with SbCl₃ gave high molecular weight oligomers (M?_n ≥ 700) in good yield (>80 wt.-%) with low dimer contents (5–17 wt.%). The other metal halides, both in the absence and presence of SbCl₃, gave large amounts (20–40 wt.-%) of dimers along with low molecular weight oligomers. ¹H NMR analysis of the obtained oligomers showed that they consist of two isomerized repeating units, one ( 1 ) unsaturated (with a cyclohexene ring) and the other ( 2 ) saturated (with a bornyl structure). The oligomers obtained with aluminium halides/SbCl₃ contained higher amounts of unsaturated units 1 than those with aluminium halides alone. The higher the molecular weight, the larger the content of 1 . Isomerization of α-pinene slightly occurred in the course of the polymerization, and the structure of the isomers depended on the catalyst systems. These results show that the aluminium halide/SbCl₃ binary systems promote the ring-opening of the cyclobutane unit in α-pinene to give higher molecular weight oligomers.     

Propene polymerization with Mg(OEt)2-supported TiCl4 catalyst, 1. Catalyst composition and behavior

Catalysts obtained from TiCl₄ and ball-milled Mg(OEt)₂ in the presence of a halide compound (dichloroethane, chlorobenzene or dichlorobenzene) and/or an internal donor (ethyl benzoate or diisobutyl phthalate) were prepared for propene polymerization. The composition of the catalysts was analyzed by IR, GC, atomic absorption spectroscopy and titration. The exchange reaction between the ethoxy group of the support and the chloride group of TiCl₄ was found to depend profoundly on the halide compound and/or the internal donor used. The propene polymerizations were carried out using various Mg(OEt)₂-supported catalysts and triethylaluminium as cocatalyst with or without external donor (triethoxyphenylsilane). The catalyst activity and stereospecificity were examined.     

Cationic polymerization of α·β-disubstituted olefins. Part XI. Polymerization of 2-chloroethyl propenyl ether catalyzed by BF3·O(C2H5)2

2-Chloroethyl propenyl ether (CEPE) was synthesized, and its cationic polymerizability by BF₃·O(C₂H₅)₂ and the steric structure of the resulting polymer were studied. In the polymerization in toluene at ?78°C, the rate of consumption of monomers decreased in the following order: cis-CEPE > 2-chloroethyl vinyl ether > trans-CEPE. The steric structure of the β-methyl group of the resulting polymer was determined quantitatively on the basis of the NMR spectrum of the β-methyl protons decoupled from β-methine protons. In the polymerization of CEPE in toluene at ?78°C, the polymer obtained from trans-CEPE was rich in threo-meso structure whilst cis-CEPE gave a polymer containing almost the same amount of threo-meso and erythro-meso structures. With methylene chloride as solvent, the amount of threo-meso structure increased and that of erythro-meso structure decreased for the polymer obtained from cis-CEPE. The steric structure of the polymer obtained from trans-CEPE was independent of the nature of the solvent used. The effect of polymerization temperature on the steric structure of the polymers was also investigated.     

The role of additives for the improvement of δ-TiCl3 catalyst performance

The influence of ethylaluminium compounds (AIEt₃ and AICIEt₂) modified by 2,6-di-tert-butyl-4-methylphenol (BHT), tributylamine (TBA) and triphenylphosphine (TPP) on the polymerization of propene was investigated using catalysts based on TiCI₃ modified by internal Lewis bases. Two catalysts were employed in this study, one (Cat. A) was prepared by the reduction of TiCI₄ complexed with dibutyl ether (DBE)—mole ratio DBE/TiCI₄ = 0,67—with AlClEt₂ and the other one (Cat. B) was prepared in the same way, but a second internal base (ethyl benzoate (EB)) was added in a mole ratio EB/TiCl₃ = 0,04. Activity and stereospecificity of the catalyst systems were strongly affected by these modified cocatalysts. The role of the modifiers is discussed.     

Ethylene/propene copolymerization in the presence of the homogeneous catalyst system Ti(Oi-C3H7)4/Al(C2H5)2F

The behaviour of the homogeneous catalyst system Ti(Oi-C₃H₇)₄/Al(C₂H₅)₂F in ethylene/propene copolymerization was studied. The copolymer structure is discussed in view of the stereoregulation mechanism previously proposed for vanadium-based homogeneous catalyst systems.     

Stereospecific polymerization of higher α-olefins with the solvay type catalyst TiCl3/Cp2Ti(CH3)2

Polymerizations of higher α-olefins (C₁₀–C₂₀) were carried out at 40°C in heptane, using the following three catalysts which differ in the isospecificity for propene polymerization: Solvay type TiCl₃/Cp₂TiMe₂((A) highly isospecific), Solvay type TiCl₃/AlEt₃((B) isospecific) and TiCl₃.3Py/MgCl₂/AlEt₃((C) aspecific). The isospecificity of the catalysts was found to decrease in the following order: (A) ? (B) ? (C), which agrees well with the results obtained in propene polymerization. The crystallinity of these polymers is discussed in brief.     

4-(α,α-dimethylbenzyl)phenyl methacrylate, 2. Polymerization in N,N-dimethylformamide

The polymerization rate of 4-(α,α-dimethylbenzyl)phenyl methacrylate in DMF at 70°C is of the order 1,6 in [monomer] and first order in [AIBN], which deviates from classical kinetics. This could be reconciled by a reaction scheme in which dimeric monomer associates and a spontaneous termination are postulated. The scheme is supported by the dependence of the kinetic chain length, v, on the 1,6-th power in [monomer] and zeroth power in [AIBN]. The degree of polymerization is smaller than v, which indicates some chain transfer. A remarkable feature is the constancy of the dispersion degree, M?_w/M?_n, of the polymers of about 1,4 up to high degrees of conversion. The overall activation energy of the polymerization, E_a, is 60,1 kJ · mol^?1, and the preexponential factor ln A ≈ 15,5 (A in (mol · dm^?3)^?1,5 · s^?1). The polymer chains seem to have a rod-like character in THF as deduced from the Mark-Houwink exponent of 1,46. In toluene the polymer tends to form associates.     

The production of 3aα-H-4α-(3′-propionic acid)-5α-hydroxy-7aβ-methylhexahydro-1-indanone-δ-lactone by Nocardia restricta mutants

Two mutants of Nocardia restricta breakdown androst-4-ene-3,17-dione into 3aα-H-4α-(3′-propionic acid)-5α-hydroxy-7aβ-methylhexahydro-l-indanone-δ-lactone. The metabolic intermediates formed are very different in each mutant. One uses certain aromatic compounds very slowly. A degradation pathway for steroids by Nocardia restricta has been proposed.     

Polymerization of ethylene with Cr[OC(CH3)3]4/Al(C2H5)2Cl as catalyst modified with some metal chlorides

Polymerization of ethylene was carried out in toluene using the homogeneous catalytic system Cr[OC(CH₃)₃]₄/Al(C₂H₅)₂Cl, combined with various metal chlorides (MtCl_x). The polymerization activity was found to be strongly dependent upon the MtCl_x used. A clear correlation was found between the activity and the elctronegativity X(Mt^x+) of the metal ion in MtCl_x. MtCl_x containing metal ions with X(Mt^x+) < 8,5 (electronegativity of the active Cr²⁺) show a markedly increased activity, whereas those with X(Mt^x+) > 8,5 have a rather decreased activity. Thus, for example, the catalyst combined with MgCl₂ shows very high activity to give a linear polyethylene with a remarkably high molecular weight and narrow molecular weight distribution. A plausible mechanism for the enhancement of the activity by suitable MtCl_x is proposed on the basis of these results.     

Synthesis and polymerization of fluorinated acrylic monomers substituted in α-position, 2. Synthesis and polymerization of 2-perfluorohexylethyl α-acetoxyacrylate

The synthesis of 2-perfluorohexylethyl α-acetoxyacrylate (^b) H₂C?C(OAc)CO₂C₂H₄C₆F₁₃ ( 1 ) was performed in two steps starting from pyruvic acid and 2-perfluorohexylethanol (3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluoro-1-octanol) with an overall yield of about 50%. Esterification of pyruvic acid with the adequate fluorinated alcohol was followed by enol acetylation to give monomer 1 . Homopolymerization and copolymerization of 1 are easily carried out. From the kinetic study of the homopolymerization and copolymerization of 1 with styrene, the numerical values of the ratio square of the rate constant of propagation over the rate constant of termination k/k_t and of the copolymerization reactivity ratios r₁ and r₂ of the two monomers were determined.     

1H and 13C NMR spectra of poly(propyl α-bromoacrylate) and poly(methyl α-bromoacrylate)

The ¹³C NMR spectra measured at 25 MHz of the methyl and propyl esters of isotactic and syndiotactic poly(α-bromoacrylate) were sufficiently resolved to be analysed for pentad tacticity sequences. The pentad tacticity of the syndiotactic polymers prepared with free radical initiators at ?40°C agreed with those calculated for Bernoullian sequence distributions based on P_r values of 0,83–0,87. The tacticities of the isotactic polymers prepared with heterogeneous catalysts were determined on the basis of these assignments. Good internal consistency was obtained between the calculated and observed pentad proportions from the quaternary and carbonyl carbon peaks in the spectra of these polymers. The order of chemical shifts for the meso and racemic dyads and tetrads in these polymers were opposite to those found in the equivalent methacrylate polymers, but as with the latter, the ¹³C-T₁ values were longer in the isotactic than in the syndiotactic polymers.