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.     

Polymerization of acetylene with Ti(OC4H9)4/butyllithium as catalyst system and silicone oil as reaction medium

A polymerization reaction catalyzed by Ti(OC₄H₉)₄/butyllithium in a reaction medium of silicone oil yields a homogeneous and highly conductive polyacetylene when doped with iron (III) chloride. The effect of the transition metal halide on polyacetylene was studied by solution doping with FeCl₃/nitromethane as a function of time.     

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.     

A combined NMR and electron spin resonance investigation of the (C5(CH3)5)Ti(CH2C6H5)3/B(C6F5)3 catalytic system active in the syndiospecific styrene polymerization

The reaction of (C₅(CH₃)₅)Ti(CH₂C₆H₅)₃ with B(C₆F₅)₃ in chlorobenzene at 25°C produces a mixture of [(C₅(CH₃)₅)Ti(CH₂C₆H₅)₂]⁺ [B(CH₂C₆H₅)(C₆F₅)₃]^? ( 1 ) and Ti(III) complexes which have been characterized by NMR and electron spin resonance (ESR) spectroscopy, respectively. Spectroscopic data combined with polymerisation activity measurements suggest that a Ti(III) complex is the active species in the styrene syndiospecific polymerisation.     

Monomer-isomerization polymerization, 27. Monomer-isomerization in competition with polymerization of α-olefins with Ziegler-Natta catalysts

The monomer-isomerization was studied in the polymerization of α-olefins with the catalytic systems TiCl₃/(C₂H₅)₃Al and Ti(OC₄H₉)₄/(C₂H₅)₃Al. The isomerization to the corresponding olefins with internal double bond was found to occur during the polymerization. With the system TiCl₃/(C₂H₅)₃Al only a small amount of isomerized olefin was produced as result of the rapid polymerization of the α-olefins. Significant isomerization was observed to take place with a poor polymerization catalyst such as Ti(OC₄H₉)₄/(C₂H₅)₃Al. Isomerization and polymerization of α-olefins with Ziegler-Natta catalysts were found to depend on the oxidation state of titanium.     

Organoaluminum catalysts for polymerization reactions. The effect of metal hydroxides on the catalytic activity of the Al(C2H5)3/H2O system

The catalytic activity of the system Al(C₂H₅)₃/H₂O was investigated. Instead of pure water aqueous solutions of inorganic bases were reacted with Al(C₂H₅)₃ in toluene/diethyl ether media. A uniform soft gel-like product was readily obtained in this reaction (H₂O/Al(C₂H₅)₃ ～ 1.0–1.5) differing from the heterogeneous nature of the product obtained with pure water. The polymerization of acetaldehyde proceeded with higher stereo-regularity in this system Al(C₂H₅)₃/aqueous inorganic base. The polymerization behavior and the stoichiometric reaction between the catalyst and the monomer (ethyl acetate formation) indicate that there seem not to be significant differences in the active species of Al(C₂H₅)₃/aqueous inorganic base and Al(C₂H₅)₃/H₂O systems. Improved stereospecific polymerization in the presence of inorganic bases is discussed with respect to the formation of a cross-linked product in the Al(C₂H₅)₃/H₂O system in the preparation of the catalyst.     

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.     

Propene polymerization with δ-TiCl3/AlCl(C2H5)2 and δ-TiCl3/Al(C2H5)3 catalyst systems, 1. Effect of external donors

The effect of ethyl benzoate (EB), diisobutyl phthalate (DIBP), dibutyl ether (DBE) and triethoxy(phenyl)silane (EPS) as third components on the propene polymerization with the catalyst systems δ-TiCl₃/AlCl(C₂H₅)₂ and δ-TiCl₃/Al(C₂H₅)₃ was investigated. The influence of external donors on the isotacticity, catalyst activity and average molecular weight (M _v) was tested. If external donors are employed, M _v decreases, the insoluble fraction in boiling isooctane increases and the catalyst activity is strongly influenced by the mole ratio external donor/TiCl₃. The results indicate that all external donors employed have the same qualitative effect on catalytic active centers.     

Polymerization of styrene with the VOCl3/Li(iC5H11) catalyst system

The polymerization of styrene with the VOCl₃/Li(iC₅H₁₁) catalyst system has been studied. Rates of polymerization fall sharply with increase in Li/V ratio; the molecular weights, however, show a maximum at Li/V = 1. Polymerization is first order with respect to catlyst as well as monomer concentrations. Activation energy was found to be 5.67 kcal/mole. Zinc diethyl acts as chain transfer agent. There was no effect of trans-stilbene on molecular weights as well as on rate of polymerization. Valence of vanadium at Li/V molar ratio 1 is 4.12 and it decreases with increase in ratio.     

TiCl4/MgH2-supported Ziegler-type catalyst system, 4. The influence of 14CO contact time and mole ratio Al(C2H5)3/Ti on concentration of active sites in ethylene homo- and copolymerization

The effect of varying ¹⁴CO contact time upon the concentration of active centres C* in ethylene homopolymerization using the TiCl₄/MgH₂ · Al(C₂H₅)₃ catalytic system shows that the polymer radioactivity, and hence C*, increase sharply in the first sixty minutes of ¹⁴CO contact with the polymerization centres. For contact times longer than one hour, the polymer radioactivity continues to increase, but very slowly. Studies on the effect of the mole ratio Al(C₂H₅)₃/Ti on ethylene homopolymerization show that both the catalytic activity and C* increase sharply when increasing the mole ratio Al(C₂H₅)₃/Ti in the range from 5 to 20. When increasing the mole ratio Al(C₂H₅)₃/Ti above 50, C* tends to decrease very slightly. In ethylene/1-hexene copolymerization a similar effect of the mole ratio Al(C₂H₅)₃/Ti on the polymerization is observed. However, even though the catalytic activity in copolymerization is observed to be higher than in homopolymerization, at the same mole ratio Al(C₂H₅)₃/Ti, yet C* in both cases is found to be more or less the same.     

Acyclic diene metathesis (ADMET) polymerization using aryloxy tungsten-based classical catalytic systems

The range of ADMET polymerization active catalysts has been expanded to include classical catalytic systems. The acyclic diene metathesis (ADMET) polymerization of hydrocarbon dienes has been performed using the aryloxy-tungsten complexes WCl₄(O-2,6-C₆H₃Ph₂)₂ ( 4 ), W(O)Cl₂(O-2,6-C₆H₃Br₂)₂ ( 5 ), and WCl₄(O-2,6-C₆H₃Br₂)₂ ( 6 ) as the precatalytic species in combination with tetrabutyltin, tetramethyltin and tri-n-butyltin hydride as the cocatalytic entities. High molecular weight polyoctenylene and polyheptenylene are obtained under bulk polymerization conditions. The scope of these classical metathesis catalysts in the polymerization of other hydrocarbon as well as functionalized dienes is studied, revealing significant reactivity differences with respect to the previously studied well-defined metathesis catalysts and providing insights into the identification of suitable classical systems for ADMET polymerization.     

The effect of preparation conditions on the catalyst Nd(P507)3/H2O/Al(i-Bu)3 for the polymerization of styrene

The catalyst system neodymium phosphonate Nd(P₅₀₇)₃ /H₂O/Al(i-Bu)₃ for the polymerization of styrene was examined. Effects of the addition order of the catalyst components, catalyst aging time and aging temperature on the catalyst activity and the polymer characteristics were investigated. The catalyst activity for isospecific polymerization of styrene increases with aging time and reaches the maximum with a catalyst aged for 45 min at 70°C. The aging time that the catalyst needs to reach the highest activity for isospecific polymerization decreases with increasing aging temperature. The preformed catalyst and the in situ catalyst were compared with respect to the kinetic behavior of the styrene polymerization and the polymer characteristics.     

Calorimetric study of 5-trimethylsilyl-2-norbornene,of its polymerization process and of poly(5-trimethylsilyl-2-norbornene) from 5 to 600 K at standard pressure

Thermodynamic properties of 5-trimethylsilyl-2-norbornene (TMSNB) and poly(5-trimethyl-silyl-2-norbornene) (PTMSNB), viz. the temperature dependence of the isobaric heat capacity C^o_p of the monomer between 10 and 330 K and of the polymer from 7 to 600 K, were studied by adiabatic vacuum and differential dynamic calorimetry. Temperature and enthalpy of monomer melting as well as parameters of glass transition and glassy state of the monomer and the polymer were determined. From the experimental data, the thermodynamic functions H°(T)-H°(0), S°(T) and G°(T)-H°(0) were calculated for TMSNB in the range of 0 to 330 K and for PTMSNB from 0 to 380 K. In a differential automatic calorimeter, the enthalpy of polymerization of TMSNB to PTMSNB in toluene solution was measured at T = 301 K and p = 101,325 kPa. Under similar physical conditions and in the same calorimeter, enthalpies of dissolution for the monomer and the polymer were estimated. The results were used to calculate the enthalpy, entropy and Gibbs function of bulk polymerization of TMSNB in the range of 0 to 380 K at standard pressure. The ceiling temperature of the polymerization process was also evaluated.     

Polymerization of propylene to syndiotactic polymer. III. Behaviour of the catalyst system VCl4-Al(C2H5)2Cl in the presence of lewis bases

Polymerizations of propylene to syndiotactic polymer have been carried out in the presence of the catalyst system VCl₄-Al(C₂H₅)₂Cl-anisole. The data obtained have been related to those previously reported concerning the catalyst system, VCl₄-Al(C₂H₅)₂Cl. It was thus possible to propose a mechanism of formation of the catalytic complexes and to put forward or confirm some hypotheses on their constitution. A polymerization mechanism is also proposed that can justify both the type of stereoregularity of the polymer and the variation of steric regularity on varying the polymerization conditions.     

Polymerisation von acetylenderivaten. IV. Mitt.: Die ionische polymerisation von phenylacetylen

The paper deals with the ionic polymerization of phenylacetylene in the presence of complex organo-metallic catalysts soluble in hydrocarbons of the type: Al(C₂H₅)₃/Ti(OC₄H₉)₄; Al(C₂H₅)₃/TiCl₂(C₅H₅)₂; Al(C₂H₅)₃/VO(C₅H₇O₂)₂; Al(C₂H₅)₃/Cr(C₅H₇O₂)₃; Al(C₂H₅)₃/Co(C₅H₇O₂)₃. A high catalytic activity of the complexes was found at certain molar ratios. The kinetics of the ionic mechanism of the polymerization have been investigated and the polymers obtained have been characterized. A study has been carried out with respect to the polydispersity of the polymers obtained in the presence of the catalytic system Al(C₂H₅)₃/Ti(OC₄H₉)₄. The activity of macroions and macroradicals of polyphenylacetylene with regard to the formation of macromolecular chains is discussed.     

Metal-containing initiator systems, 34. Polymerization of vinyl monomers initiated by the binary system cobaltocene/bis(ethyl acetoacetato)copper (II)

The effect of some metallocenes such as ferrocene (Fe(C₅H₅)₂), nickelocene (Ni(C₅H₅)₂), and cobaltocene (Co(C₅H₅)₂), on the vinyl polymerization initiated with bis(ethyl acetoacetato)-copper(II) (Cu(eacac)₂) was investigated. Co(C₅H₅)₂ was found to exert a markedly accelerating effect on the polymerization of methyl methacrylate (MMA) with Cu(eacac)₂. The polymerization of MMA with the system Co(C₅H₅)₂/Cu(eacac)₂ at 50°C was found to be fairly affected by the solvent used. The results of copolymerization of MMA with styrene (St) and the effect of hydroquinone (HQ) on the polymerization of MMA with Co(C₅H₅)₂/Cu(eacac)₂ showed that the polymerization proceeds via a radical mechanism. The polymerization of MMA with Co(C₅H₅)₂/Cu(eacac)₂ was studied kinetically in acetone. The overall activation energy of the polymerization was calculated to be 86,3 kJ/mol (20,6 kcal/mol). This value was somewhat higher than that (17,6 kcal/mol) obtained for the polymerization of MMA with Cu(eacac)₂ alone. The polymerization rate (R_p) is represented by the following equation: R_p = k[Co(C₅H₅)₂]^0,5 [Cu(eacac)₂]^0,2 [MMA]^1,3. The high order in monomer concentration suggests a participation of the monomer in the initiation process of this polymerization. This is supported by the examination of the ESR spectrum of the system Co(C₅H₅)₂/Cu(eacac)₂/MMA/acetone, where reduction of Cu(II) to Cu(I) occurs. To elucidate the initiation mechanism, the spin trapping technique was applied to the system Co(C₅H₅)₂/Cu(eacac)₂/methyl acrylate. From these results, an initiation mechanism for the binary initiator system Co(C₅H₅)₂/Cu(eacac)₂ is proposed and discussed.     

Conformational stability and force field of polyphosphazenes: MNDO calculations,vibrational spectra and normal coordinate analyses of [NP(R)2]n (R = Cl,OCH2CF3, OC6H5)

Raman and Fourier-transform Raman spectra (1500 ? 100 cm^?1) of (PCl₂N)_n (PDCP) were recorded in the solid phase and in solution at room temperature. Raman (3 500 ? 100 cm^?1) and infrared (4 000 ? 200 cm^?1) spectra of [P(OCH₂CF₃)₂N]_n (PDFP) and [P(OC₆H₅)₂N]_n (PDPP) were recorded in the solid phase and at different temperatures (in the case of Raman spectroscopy). The conformation of the isolated macromolecule PDCP is assumed to be analogous to the geometry of the Cl₂(O)PN(PCl₂N)₆PCl₃ oligomer optimized by the use of MNDO (modified neglect of diatomic overlap) calculations. The optimized cis-trans conformation is in good agreement with the X-ray experimental data concerning the polymer. The calculated low energy barriers around the PN bond along the chain axis can explain the flexibility of the phosphazene backbone and the elastomeric properties of the polymers. The MNDO calculation of the harmonic force field of Cl₂(O)PN(PCl₂N)₆PCl₃ is in reasonable agreement with the experimental values for (PCl₂N)_n in solution as well as in the amorphous phase. The normal coordinate analyses of (PCl₂N)_n were undertaken according to several structural hypotheses using a force field derived from linear short-chain molecules. The Raman spectra of PDCP in solution or in the amorphous phase are in reasonable agreement with the vibrational frequencies calculated for a planar cis-trans macromolecule and have a striking resemblance with those of linear short-chain analogs Cl₂(O)PN(PCl₂N)_n PCl₃ (n = 1,2). The Raman and infrared spectra of the substituted polymers PDFP and PDPP are dominated by the characteristic features of the chain substituents.     

Polymerization of methyl methacrylate initiated by a Rh(I) complex and benzoyl peroxide

The polymerization of some vinyl monomers initiated by carbonylchlorobis(triphenylphos-phine)rhodium(I) (RhCl(CO)(P(C₆H₅)₃)₂) and benzoyl peroxide (BPO) was studied. The polymerization ability was found to decrease in the following order: methyl methacrylate (MMA) > styrene > vinyl acetate > isobutyl vinyl ether. In the polymerization of MMA, the average molecular weight increases with an increase in monomer conversion. On the basis of the kinetic studies of the polymerization of MMA initiated by RhCl(CO)(P(C₆H₅)₃)₂ and BPO (the mole ratic [BPO]/[RhCl(CO)(P(C₆H₅)₃)₂]) was between 1 and 7, the rate of polymerization, R_p' can be expressed by the following equation: The overall activation energy for the MMA polymerization was found to be 75,3 kJ/mol within the temperature range of 50 to 80°C. The composition curve of the copolymerization of styrene with MMA using RhCl(CO)(P(C₆H₅)₃)₂ and BPO agrees with that of the ordinary radical polymerization. On the basis of these results the initiation mechanism is discussed.     

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.     

On the 1,4‐cis‐Polymerization of Butadiene with the Highly Active Catalyst Systems Nd(C3H5)2Cl·1.5 THF/Hexaisobutylaluminoxane (HIBAO), Nd(C3H5)Cl2· 2 THF/HIBAO and Nd(C3H5)Cl2·2 THF/Methyl‐aluminoxane (MAO) – Degree of Polymerization,Polydispersity, Kinetics and Catalyst Formation

The allylneodymium chloride complexes Nd(C₃H₅)₂Cl·1.5 THF and Nd(C₃H₅)Cl₂·2 THF can be activated by adding hexaisobutylaluminoxane (HIBAO) or methylaluminoxane (MAO) in a ratio of Al/Nd = 30 for the catalysis of butadiene 1,4‐cis‐polymerization. A turnover frequency (TOF) of about 20 000 mol butadiene/(mol Nd·h) and cis‐selectivity of 95–97% are achieved under standard conditions ([BD]₀ = 2 m, 35°C, toluene). Molecular weight determinations indicate a low polydispersity (M̄_w (LS)/M̄_n (LS) = 1–1.5), the formation of only one polymer chain per neodymium and the linear increase of the degree of polymerization (DP) with the butadiene conversion, as observed for living polymerizations. First indications of chain‐transfer reaction occur only at the highest conversion or degree of polymerization. The rate law r_P = k_P[Nd][C₄H₆]^1.8 is derived for the catalyst system Nd(C₃H₅)₂Cl·1.5 THF/HIBAO and for the system Nd(C₃H₅)Cl₂·2 THF/MAO the rate law r_P = k_P[Nd] [C₄H₆]² with k_P = 3.24 L²/(mol²·s) (at 35°C). Taking into account the Lewis acidity of the alkylaluminoxanes and the characteristic coordination number of 8 for Nd(III) in allyl complexes the formation of an η³‐butenyl‐bis(η⁴‐butadiene)neodymium(III) complex of the composition [Nd(η³‐RC₃H₄)(η⁴‐C₄H₆)₂(X‐{AlOR}_n)₂] is assumed to be a single‐site catalyst for the chain propagation by reaction of the coordinated butadiene via the π‐allyl insertion mechanism and the anti‐cis and syn‐trans correlation to explain the experimental results.