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.     

Propylene polymerization with dimethylsilylbis(3-methylcyclo-pentadienyl)MCl2 [M = Ti,Zr, Hf] in combination with methylaluminoxane

Propylene polymerizations with rac-dimethylsilylbis(3-methylcyclopentadienyl)MCl₂ (M = Ti, Zr, Hf) in combination with methylaluminoxane (MAO) were carried out to study the effect of the metal species on catalytic activity, stereoregularity, regioregularity, and molecular weight of poly(propylene). The rac-Me₂Si(3-MeCp)₂TiCl₂/MAO catalyst showed lowest activity among the three catalysts. The stereospecificity of the titanium based catalyst is very high and the portion of the mmmm pentads is roughly as high as for the zirconium and hafnium analogue. On the other hand, the regiospecificity of the titanium based catalyst is low and only the 1,3-regioirregular structure was observed, whereas the 2,1-regioirregular structure was detected in poly(propylene)s obtained with the zirconium and hafnium analogue. As a result, the melting point of poly(propylene) obtained with the titanium based catalyst is lower than that of poly(propylene) obtained with the zirconium or hafnium analogue. Addition of hydrogen with the titanium based catalyst gave rise to an increase in activity; but this accelerating effect was not observed in ethylene polymerization.     

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.     

Propene polymerization with MgCl2-supported transition metal catalysts activated by Cp2MtMe2(Mt = Ti,V, Zr,Hf)

Several kinds of MgCl₂-supported catalysts were prepared by grinding the mixtures of MgCl₂ and MtCl_n(MtCl_n = TiCl₄, ZrCl₄, HfCl₄, VCl₃). Polymerization of propene was conducted at 40°C and 1 atm with these solid catalysts by using Cp₂MtMe₂ (Mt = Ti, Zr, Hf, V) as cocatalyst. Polymerization took place only with the use of the TiCl₄/MgCl₂ catalyst. Both the activity and isospecificity were found to strongly depend upon the cocatalyst used. The polymers produced were fractionated with boiling heptane and analyzed by means of ¹³C NMR, the results of which suggested the existence of two types of catalytic centers, isospecific and aspecific. Plausible models of these catalytic centers are proposed.     

Synthesis and basic characteristics of polypropene-block-poly(ethene-co-propene) by modified stopped-flow polymerization with an MgCl2-supported Ziegler catalyst

A well-defined diblock copolymer, polypropene-block-poly(ethene-co-propene), was synthesized by modified stopped-flow polymerization with an MgCl₂-supported Ziegler catalyst. The copolymer shows a unimodal gel permeation chromatography (GPC) elution curve without any material in the low molecular weight region. The molecular weight can be controlled by the polymerization time (ca. 0.1 to 0.2 s). Furthermore, the elution pattern by cross fractionation chromatography showed that the block copolymer eluted at each temperature region between 0°C to 120°C is composed of a uniform material. After extraction with heptane, the ¹³C NMR spectra showed that the signals from poly(ethene-co-propene) remain unchanged in the block copolymer but are absent in a corresponding polypropene/poly(ethene-co-propene) blend. The results of differential scanning calorimetry (DSC) and optical microscopic observation indicate not only the formation of a block copolymer with a chemical linkage between the polypropene block and the poly(ethene-co-propene) block, but also the regulation of the crystalline morphology in the block copolymer by changing the composition.     

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.     

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.     

Propene polymerization in the presence of MgCl2-supported Ziegler-Natta catalysts, 5. Microstructural characterization of the “isotactic” (heptane-insoluble) polypropene fractions

The stereosequence distribution in the heptane-insoluble fraction of polypropene samples prepared with a number of MgCl₂-supported catalysts was analyzed in detail by means of ¹³CNMR. The results indicate that what is conventionally taken as “isotactic” polypropene is normally a stereoblock polymer, in which at least part of the macromolecules contain long isotactic blocks spaced by much shorter “syndiotactoid” sequences. This implies that the active sites responsible for the formation of the two types of stereosequences are able to interconvert reversibly on the surface of the MgCl₂ support in times which may be shorter than the average growth times of the polymer molecules. Possible models of active sites apt to explain the observed polymerization behavior are also briefly 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.     

Synthesis of MgCl2-supported dichlorobis(4,4,4-trifluoro-1-phenyl-1,3-butanedionato)titanium catalysts with different titanium contents and their application to propene polymerization

Various MgCl₂-supported Ti(4,4,4-trifluoro-1-phenyl-1,3-butanedionato)₂Cl₂ catalysts with different Ti contents (0.017 ∼ 0.002 mmol/g) were synthesized and applied to propene polymerization using triethylaluminium and di-i-propyldimethoxysilane (DIPDMS) as the cocatalyst and external donor, respectively. When polymerization was conducted in the absence of DIPDMS, neither the activity nor the isospecificity of catalyst were dependent upon the Ti content. However, the effect of DIPDMS on the catalyst performance was found to be markedly dependent upon the Ti content, i.e., the addition of DIPDMS to the catalyst with low Ti content caused a prominent increase in the activity for isotactic polymerization. As a result, the present catalyst with low Ti content gave a highly isotactic polypropene with T_m = 169.3°C and [mmmm] > 99% in high selectivity (I.I. = 97.7%).     

Protection and polymerization of functional monomers, 14. Anionic living polymerization of 4-[N,N-bis(trimethylsilyl)-aminomethyl]styrene and 4-{2-[N,N-bis(trimethylsilyl)amino]ethyl}styrene

Anionic polymerization of 4-[N,N-bis(trimethylsilyl)aminomethyl]styrene ( 1 ) and 4-{2-[N,N-bis(trimethylsilyl)amino]ethyl}styrene ( 2 ) were carried out at ?78°C in tetrahydrofuran (THF)/pentane mixtures with butyllithium, oligo(α-methylstyryl)lithium, oligo(α-methylstyryl)potassium, and cumylpotassium. Polymerizations of 1 and 2 proceed without chain transfer and termination reactions to give stable “living polymers” when butyllithium or oligo(α-methylstyryl)lithium are used as initiator. The resulting polymers have predictable molecular weights and narrow molecular weight distributions (ratio of weight- to number-average molecular weights, M?_w/M?_n = 1,04–1,14). Under mild acidic conditions (pH 3–5 in THF/water), cleavage of the N? Si bonds in the polymers is completely achieved to give well-defined poly(4-aminomethyl)styrene and poly[4-(2-aminoethyl)styrene]. The triblock copolymers of polystyrene-block-poly( 1 )-block-polystyrene and polystyrene-block-poly( 2 )-block-polystyrene are readily prepared in quantitative yields by sequential polymerization of styrene with living poly( 1 ) or living poly( 2 ).     

Propylene Polymerization Behavior of Fluorinated Bis(phenoxy‐imine) Ti Complexes with an MgCl2‐Based Compound (MgCl2‐Supported Ti‐Based Catalysts)

Summary: Fluorinated bis(phenoxy‐imine)Ti complexes 1 – 3 combined with MgCl₂/i‐Bu_nAl(OR)_3−n (MgCl₂‐supported catalysts) were able to polymerize propylene in a living fashion at room temperature to provide slightly to highly syndiotactic poly(propylenes) (PPs) with extremely narrow distributions of molecular weight. These represent the first examples of MAO‐ and borate‐free group 4 metal‐based living catalysts. The supported complexes 2 and 3 formed PPs with higher syndiotacticity and T_m's than the corresponding homogeneous MAO‐activation systems (e.g., 3 : rr 97%, T_m 155 °C; MAO activation: rr 93%, T_m 152 °C). The measured T_m of 155 °C represents the highest known T_m for syndiotactic PPs synthesized at room temperature.

Polymerization of propylene to poly(propylene) with supported Ti‐based catalysts.     

Influence of polymerization conditions on the copolymerization of styrene with ethylene using Me2Si(Me4Cp)(N-tert-butyl)TiCl2/methylaluminoxane Ziegler-Natta catalysts

Styrene was copolymerized with ethylene using Me₂Si(Me₄Cp)(N-tert-butyl)TiCl₂/methylaluminoxane (Me = methyl, Cp = cyclopentadienyl) varying monomer concentration, styrene/ethylene molar ratio and polymerization temperature. Increasing styrene or decreasing ethylene concentration, respectively, in the monomer feed lowered both activity of the catalyst system and molecular weight of the copolymer. Only at low styrene content, a linear correlation of styrene concentration in the monomer feed and styrene incorporation in the copolymer was found. From copolymerizations at various temperatures the activation energy of the insertion step was calculated to be 56 kJ/mol. According to Fineman-Ross plot, the copolymerization parameters are r_E = 23,4 for ethylene and r_S = 0,015 for styrene. Investigation of the thermal properties by means of differential scanning calorimetry and dynamic mechanical analysis revealed pronounced decrease of melting temperature and increase of glass transition temperature with increasing styrene content.     

Protection and polymerization of functional monomers, 26. Synthesis of well-defined poly[4-(3′-butynyl)styrene] by means of anionic polymerization of 4-(4′-trimethylsilyl-3′-butynyl)styrene

Anionic polymerization of 4-(4′-trimethylsilyl-3′-butynyl)styrene ( 2 ) was carried out in THF at ?78°C for 0.5 h with oligo(α-methylstyryl)lithium, -dilithium, and -dipotassium. Poly( 2 )s possessing predicted molecular weights and narrow molecular weight distributions (M?_w/M?_n < 1.11) were quantitatively obtained in all cases. By sequential anionic copolymerization of 2 and styrene, novel block copolymers, polystyrene-block-poly( 2 ) starting either from living polystyrene or living poly( 2 ), were synthesized. After completion of the polymerization, there occurred some gradual deactivation of the propagating carbanion of poly( 2 ) at ?78°C. This deactivation reaction could be almost completely suppressed at ?95°C. The deprotection of poly( 2 ) was performed by treating with Bu₄NF in THF at 0°C for 1 h. The trimethylsilyl protecting group of poly( 2 ) was completely removed to afford a poly[4-(3′-butynyl)styrene] of a controlled molecular structure.     

Effects of glycine antagonists on Mg(2+)- and glycine-induced [3H]N-(1-[2-thienyl]cyclohexyl)-3,4-piperidine binding.

We investigated the effects of glycine antagonists, 3-amino-1-hydroxy-2- pyrrolidone (HA-966), 7-chlorokynurenic acid (7-Cl-KYNA), 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), 6,7-dichloro-3-hydroxy-2-quinoxalinecarboxylic acid (DHQXC), 6,7-dichloroquinoxaline-2,3-dione (DCQX), and 5-chloro-indole-2-carboxylic acid (5-Cl-I2CA), on Mg(2+)- and glycine-induced [3H]N-(1-[2-thienyl]cyclohexyl)-3,4-piperidine ([3H]TCP) binding to well-washed rat cortical membranes. Except for 5-Cl-I2CA, all the glycine antagonists completely inhibited not only glycine- but also Mg(2+)-induced [3H]TCP binding in a concentration-dependent manner. Out of all the glycine antagonists examined DHQXC most selectively inhibited Mg(2+)-induced [3H]TCP binding, while DCQX was the most selective for inhibiting glycine-induced [3H]TCP binding.     

Poly(2-[α-3H]vinylpyridine 1-oxide)

Poly(2-vinylpyridine 1-oxide), when injected into animals, counteracts the pathogenic effects of inhaled silica dust. To study its distribution in the cells, a specifically labelled polymer has been synthesised by reducing 2-acetylpyridine with tritium, dehydrating, polymerising then oxidizing the polyvinyl product. Some of the tritium (17%) enters the aromatic ring by exchange and there is a small loss of tritium by exchange with solvents. At the stage of reduction, there is preference for C? T bond formation rather then C? H.     

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.