Alternating copolymer of butadiene and propylene. III

Alternating copolymerizations of butadiene with propylene and other olefins were investigated by using VO(acac)₂–Et₃Al–Et₂AlCl system as catalyst. Butadiene–propylene copolymer with high degree of alternation was prepared with a monomer feed ratio (propylene/butadiene) of 4. Alternating copolymers of butadiene and other terminal olefins such as butene-1, pentene-1, dodecene-1, and octadiene-1,7 were also obtained. However, the butadiene–butene-2 copolymerization did not yield an alternating copolymer but a trans-1,4-polybutadiene.     

Alternating stereospecific copolymerization of ethylene and propylene with metallocene catalysts

The copolymerization of ethylene and propylene with bridged metallocenes Me(2)E(3-RCp)(Flu)X(2)/MAO (E = C, X = Me; E = Si, X = Cl; R = H or alkyl) was investigated. Ethylene/propylene copolymerization with metallocenes having heterotopic active sites (R =Me, i-Pr) yield alternating, isotactic ethylene/propylene copolymers with percentages of alternating EPE+PEP triads in the range of 61-76% at 50% ethylene incorporation. Both the nature of the substituent R and the bridge E influence the copolymerization behavior including the copolymerization activity, copolymer sequence distribution, molecular weight, and stereochemistry. Silicon-bridged metallocenes produce copolymers with higher activity and molecular weight but lower propylene incorporation at similar feeds than the carbon-bridged analogues. Isotactic PEPEP sequences were observed for all metallocenes, while the tacticities of the EPPE sequences varied with the bridge and the substituent on the metallocene ligand. Isotactic PEPEP sequences and atactic EPPE sequence errors in the alternating copolymers are consistent with a mechanism where the comonomers are enchained alternately at the heterotopic coordination sites of the metallocenes. Isotactic EPPE sequences are indicative of occasional multiple insertions at the stereospecific site, caused by an isomerization of the chain prior to monomer insertion (backskip).     

Organometallic compounds as catalysts in the alternating copolymerization of acrylonitirle with butadiene

The catalytic activity of various organometallic compounds of the Lewis acid type R_mMX_n(M = Zn, Cd, B, Al; R = CH₃,C₂H₅, i-C₄H₉, C₆H₅CH₂, C₆H₅C₂H₄; X = Cl, OCH₃) in the alternating copolymerization of acrylonitrile with butadiene in bulk and in toluene solution has been studied. The activity of the catalyst was found to depend on its acidity, the strength of its M? R bond, and on the type of substituent R. The results obtained have been discussed in terms of the copolymerizability of the acrylonitrile complexed by R_mMX_n and in terms of the effect of the R_mMX_n structure on the initiation rate of the copolymerization.     

High-activity,single-site catalysts for the alternating copolymerization of CO2 and propylene oxide

Despite recent advances regarding catalysts for CO2/epoxide copolymerization, the development of high-activity catalysts for alternating polymerization of CO2 and commodity epoxides, such as propylene oxide, remains a challenge. A new class of unsymmetrically substituted beta-diiminate zinc complexes is reported that exhibits unprecedented activity for CO2/propylene oxide copolymerization. The polymers formed are of high molecular weight (Mn approximately 35 kg/mol) and have narrow polydispersities (PDI approximately 1.1), consistent with a living polymerization.     

Alternating copolymerization of isoprene and butadiene with acrylonitrile

Copolymerizations of acrylonitrile and isoprene or butadiene were carried out in the presence of a new catalytic system containing Cr(O-tert-Bu)₄ and AlEtCl₂. It was found that the copolymer compositions have a highly alternating structure, even with varying feed ratios of monomer. The nuclear magnetic resonance spectra of the copolymers obtained with this catalytic system were observed and are discussed in terms of the alternation.     

Cobalt catalysts for the alternating copolymerization of propylene oxide and carbon dioxide: combining high activity and selectivity

Synthetic pathways to (salcy)CoX (salcy = N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-diaminocyclohexane; X = halide or carboxylate) complexes are described. Complexes (R,R)-(salcy)CoCl, (R,R)-(salcy)CoBr, (R,R)-(salcy)CoOAc, and (R,R)-(salcy)CoOBzF(5) (OBzF(5) = pentafluorobenzoate) are highly active catalysts for the living, alternating copolymerization of propylene oxide (PO) and CO(2), yielding poly(propylene carbonate) (PPC) with no detectable byproducts. The PPC generated using these catalyst systems is highly regioregular and has up to 99% carbonate linkages with a narrow molecular weight distribution (MWD). Inclusion of the cocatalysts [PPN]Cl or [PPN][OBzF(5)] ([PPN] = bis(triphenylphosphine)iminium) with complex (R,R)-(salcy)CoCl, (R,R)-(salcy)CoBr, or (R,R)-(salcy)CoOBzF(5) results in remarkable activity enhancement of the copolymerization as well as improved stereoselectivity and regioselectivity with maximized reactivity at low CO(2) pressures. In the case of [PPN]Cl with (R,R)-(salcy)CoOBzF(5), an unprecedented catalytic activity of 620 turnovers per hour is achieved for the copolymerization of rac-PO and CO(2), yielding iso-enriched PPC with 94% head-to-tail connectivity. The stereochemistry of the monomer and catalyst used in the copolymerization has dramatic effects on catalytic activity and the PPC microstructure. Using catalyst (R,R)-(salcy)CoBr with (S)-PO/CO(2) generates highly regioregular PPC, whereas using (R)-PO/CO(2) with the same catalyst gives an almost completely regiorandom copolymer. The rac-PO/CO(2) copolymerization with catalyst rac-(salcy)CoBr yields syndio-enriched PPC, an unreported PPC microstructure. In addition, (R,R)-(salcy)CoOBzF(5)/[PPN]Cl copolymerizes (S)-PO and CO(2) with a turnover frequency of 1100 h(-1), an activity surpassing that observed in any previously reported system.     

Kinetic study of the alternating copolymerization of butadiene and methyl methacrylate

A kinetic investigation of the alternating copolymerization of butadiene and methyl methacrylate with the use of a system of ethylaluminum dichloride and vanadyl chloride as a catalyst was undertaken. The relation between the polymer yield and the molar fraction of methyl methacrylate in the feed was examined by continuous variation of butadiene and methyl methacrylate, the concentrations of total monomer, ethylaluminum dichloride, and vanadyl chloride being kept constant. This continuous variation method revealed that the polymer yield attains its maximum value with a monomer feed containing less than the 0.5 molar fraction of methyl methacrylate. This value of the molar fraction of methyl methacrylate affording the maximum polymer yield decreased on increasing the total monomer concentration but was not changed on varying the concentration of ethylaluminum dichloride. The number of active species estimated from the relation between yield and molecular weight of the polymer was almost constant, regardless of the molar fraction of methyl methacrylate in the feed. Consequently, it can be said that the maximum polymer yield depends mainly on the propagation reaction, not on the initiation reaction or the termination reaction. Three types of the mechanism have been discussed for this alternating copolymerization: polymerization via alternating addition of butadiene and methyl methacrylate complexed with ethylaluminum dichloride by the Lewis-Mayo scheme; polymerization via the ternary intermediate of butadiene, methyl methacrylate, and ethylaluminum dichloride; polymerization via the complex formation of butadiene and methyl methacrylate complexed with ethylaluminum dichloride occurring only at the growing polymer radical. From the kinetic results obtained, it was shown that the first and third schemes are excluded, and polymerization by way of the ternary intermediate is compatible with the data.     

Homo- and copolymerization of butadiene and styrene with neodymium tricarboxylate catalysts

Homo- and copolymerizations of butadiene (BD) and styrene (St) with rare-earth metal catalysts, including the most active neodymium (Nd)-based catalysts, have been examined, and the cis-1,4 polymerization mechanism was investigated by the diad analysis of copolymers. Polymerization activity of BD was markedly affected not only by the ligands of the catalysts but also by the central rare-earth metals, whereas that of St was mainly affected by the ligands. In the series of Nd-based catalysts [Nd(OCOR)₃:R = CF₃, CCl₃, CHCl₂, CH₂Cl, CH₃], Nd(OCOCCl₃)₃ gave a maximum polymerization activity of BD, which decreased with increasing or decreasing the pKa value of the ligands. This tendency was different from that for Gd(OCOR)₃ catalysts, where the CF₃ derivative led to the highest polymerization activity of BD. For the polymerization of St and its copolymerization with BD, the maximum activities were attained at R = CCl₃ for both Nd- and Gd-based catalysts. The copolymerization of BD and St with Nd(OCOCCl₃)₃ catalyst was also carried out at various monomer feed ratios, to evaluate the monomer reactivity ratios as r_BD = 5.66 and r_St = 0.86. The cis-1,4 content in BD unit decreased with increasing St content in copolymers. From the diad analysis of copolymers, it was indicated that Nd(OCOCCl₃)₃ catalyst controls the cis-1,4 structure of the BD unit by a back-biting coordination of the penultimate BD unit. Furthermore, the long range coordination of polymer chain by the neodymium catalyst was suggested to assist the cis-1,4 polymerization. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 241–247, 1998     

Alternating stereospecific copolymerization of cyclopentene and ethylene with constrained geometry catalysts

The stereoselective copolymerization of cyclopentene (cP) and ethylene (E) to generate highly alternating polymers with isotactic cis 1,2-cyclopentene enchainment is reported.     

以SIO~2为载体的乙烯丙烯共聚高效Ziegler-Natta催化剂

本工作以反应法制备了sio~2负载的乙丙烯共聚高效ziegler-natta催化剂, 考察了Ticl~4/Al~2t~3l~3/Sio~2催化体系的催化效率,发现在无Mgcl~2及Mg系化合物存在下,使催化活性大大提高,并利用ESR对高效的原因进行了初步探讨,得到了一些有意义的结果.     

Hydrogenated 1,4-insertion of butadiene in the copolymerization with propylene using an isospecific zirconocene catalyst

Poly(propylene-ran-1,3-butadiene) that contained pendant vinyl groups derived from 1,2-inserted butadiene units was selectively synthesized by rac-dimethylsilylbis(2-methyl-4-phenylindenyl)zirconium dichloride (Ph-Ind) activated with modified methylaluminoxane (MMAO) in the presence of hydrogen. The copolymers obtained without hydrogen had 1,2-inserted and 1,4-inserted butadiene units. The addition of hydrogen to the copolymerization improved the activity by approximately 1000-fold and gave the copolymer only with 1,2-inserted butadiene units, of which the content was equal to the copolymer obtained without hydrogen. The 13C NMR analysis of the copolymers clarified that butadiene also inserted into the copolymer as a tetramethylene unit, of which the content was almost the same as that of 1,4-inserted butadiene units observed in the absence of hydrogen. No signal that could be assigned to cyclic structures or long branched side chains was observed. These results indicate that pi-allyl species of zirconocenes formed by 1,4-butadiene insertion at the growing polymer chain ends transformed to the tetramethylene chain end by hydrogenation and continued successive propylene insertion.     

Ethylene/POSS copolymerization behavior of postmetallocene catalysts and copolymer characteristics

Copolymerization of ethylene with iso‐butyl substituted monoalkenyl(siloxy)‐ or monoalkenylsilsesquioxane (POSS) comonomers over bis(phenoxy‐imine) and salen‐type titanium and zirconium catalysts was studied. It was found that the polyreaction performance was significantly depended by the kind of the catalyst and by the structure and concentration of POSS in the feed. The POSS comonomer was efficiently incorporated into the polymer chain at up to 0.2 mol %. The differences in the copolymer compositions as the functions of the catalyst kind and the POSS comonomer were observed, including the varied number‐average sequence length of ethylene and unsaturated end groups, as determined by ¹H NMR and FT‐IR. The presence of POSS comonomers affected also the melting and crystallization behavior of the copolymers, as evidenced by DSC, because of influence on the polymer chain arrangement. The POSS units could act as the nucleating agents. Moreover, the crystal and structural parameters of ethylene/POSS copolymers were evaluated on the basis of X‐ray results, and the limited self‐aggregation of POSS incorporated into the polymer chain, the small number and size of POSS aggregates, and the increased crystallinity degree of copolymers were demonstrated. The ethylene/POSS copolymers produced by postmetallocenes offered also high thermal stability and interesting morphological properties. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3918–3934     

Alternating copolymerization of propylene oxide and carbon dioxide with an alumina supported diethylzinc catalyst

Diethylzinc was allowed to react with γ-alumina in n-heptane at 50°C, and the copolymerization of propylene oxide and carbon dioxide was investigated in some detail at 30–90°C by using the reaction product as a catalyst. From an analysis of the catalyst it was found that diethylzinc reacted with the surface hydroxyl groups of γ-alumina mainly to give the following A-type species by evolving ethane: The catalyst showed considerably high activity for the copolymerization. The polymer obtained was a white solid with a high molecular weight soluble in benzene, acetone, dioxane, and methylene chloride and insoluble in diethyl ether and water. It was confirmed as an alternate copolymer of propylene oxide and carbon dioxide. The copolymerization was also conducted with a reaction mixture of the catalyst and catechol in which the molar ratio of catechol to the A-type species was varied. The copolymerization activity decreased linearly with an increase in the molar ratio and disappeared completely at the molar ratio of unity. On the basis of these results it has been concluded that the A-type is the true active species for the copolymerization.     

Alternating copolymerization of polar vinyl monomers in the presence of zinc chloride. I. Propagation and initiation of the copolymerization of acrylonitrile with styrene copolymer

Copolymerization of acrylonitrile with styrene spontaneously occurred on addition of zinc chloride without addition of any other radical initiator. The composition of the copolymer approached that of strictly alternating copolymer as zinc chloride added to the copolymerization system increased. The significance of the apparent monomer reactivity ratios of this copolymerization system was studied from a kinetic point of view, and it was shown that the monomer sequence distribution is indicated by the apparent monomer reactivity ratios. Further, equations which represent the relation between the apparent monomer reactivity ratios and Q,e values at a given salt concentration were derived. These equations reasonably accounted for the decrease of the apparent monomer reactivity ratios of the copolymerization of acrylonitrile with styrene in the presence of zinc chloride and the behavior of the other acrylonitrile copolymerization systems in the presence of zinc chloride. The initiation step of the spontaneous radical copolymerization of acrylonitrile with styrene in the presence of zinc chloride was explained by a cross-initiation mechanism.     

Synthesis of a polyester macromonomer via the cobalt-catalyzed alternating copolymerization of propylene oxide and carbon monoxide

The alternating copolymerization of propylene oxide and carbon monoxide was investigated with cobalt complexes. The NaCo(CO)₄/amine catalyst system selectively yielded oligo(3-hydroxybutyrate)s bearing a polymerizable crotonate end group, whereas the use of Co₂(CO)₈ as a cobalt source resulted in a smaller concentration of the crotonate end group and a high degree of polymerization. The high selectivity for the oligoesters with the crotonate end group with the NaCo(CO)₄/amine system was attributed to its more basic reaction condition. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4666–4670, 2004     

Ruthenium phosphine complexes as catalysts of alternating copolymerization of ethylene and carbon monoxide

The properties of the ruthenium (II) phosphine complexes [Ru(dppe)₂(OTs)₂] and [Ru{PhP(CH₂CH₂CH₂PPh₂)₂}(OTs)₂] as catalysts of alternating copolymerization of ethylene and carbon monoxide were studied. The catalytic activity of these complexes in the absence of cocatalysis is low, but it is substantially increased in the presence of trifluoroacetic acid or 1,4-benzoquinone. These compounds are the first ruthenium complexes which catalyze copolymerization of ethylene and CO. Translated fromAkademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1119–1121, June, 2000.     

Radiation-induced emulsion copolymerization of tetrafluoroethylene with propylene. IV. Effects of emulsifier concentration and dose rate

Radiation-induced emulsion copolymerization of tetrafluoroethylene with propylene was carried out by batch operation with an initial molar ratio of tetrafluoroethylene to propylene of 3.0 in the emulsifier concentration range of 0.1 to 3.0% and in the dose rate range of 2 × 10⁴ to 2 × 10⁵ R/hr. The effects of emulsifier concentration and dose rate on the polymerization rate and the number-average degree of polymerization are discussed in comparison with the Smith-Ewart theory. The polymerization rate is proportional to the 0.26 power of emulsifier concentration and to the 0.7 power of dose rate. The degree of polymerization is independent of the emulsifier concentration and the dose rate above the critical micelle concentration (CMC) of the emulsifier. These results are not in agreement with the Smith-Ewart theory. It is explained that the termination reaction is a degradative chain transfer of propagating radicals to propylene. On the other hand, the copolymerization in emulsion occurs either below the CMC or in the absence of emulsifier. Under these conditions, however, it is impossible to obtain a copolymer of high molecular weight at a high rate of polymerization because of the presence of a small number of polymer particles formed and the short interval of chain growth in the polymer particle.     

Two-dimensional double metal cyanide complexes: highly active catalysts for the homopolymerization of propylene oxide and copolymerization of propylene oxide and carbon dioxide

The synthesis of two-dimensional double metal cyanide complexes of the formula Co(H2O)2[M(CN)4].4H2O (M=Ni, Pd or Pt) and the X-ray crystal structure of Co(H2O)2[Pd(CN)4].4H2O are presented. The anhydrous forms of these complexes were found to be effective catalyst precursors for the homopolymerization of propylene oxide as well as the random copolymerization of propylene oxide and carbon dioxide to produce poly(propylene oxide-co-propylene carbonate) with no propylene carbonate byproduct. A detailed copolymer microstructure is proposed.     

Cationic copolymerization of tetrahydrofuran with propylene oxide. IV. Use of antimony pentachloride as catalyst

Propylene oxide and tetrahydrofuran were polymerized cationically by an in situ catalytic system composed of antimony pentachloride and 1,2-propanediol. The rates of polymerization were measured by vapor-phase chromatography in the temperature range from ?20°C to +20°C. The Arrhenius parameters pertaining to the reaction of each of the comonomers were evaluated and compared with data published earlier for other catalytic systems. The present catalyst system was incapable of initiating a homo-polymerization of tetrahydrofuran in the absence of propylene oxide, while the latter was readily homopolymerized. In a copolymerization system, the rates of consumption of both monomers were first-order in respect to the catalyst, but the reaction ceased when all of the propylene oxide had been consumed. The relative reactivity of the two monomers as characterized by the copolymerization parameters r₁ (PO) = 1.15 and r₂ (THF) = 0.70 suggests that in the copolymerization system, tetrahydrofuran is capable of a reaction with its own active center. This is discussed in terms of a possible mechanism involving the effects of penultimate units and extensive chain transfer. The latter is well evident from the molecular weights of resulting copolyethers, which do not exceed one thousand.