Polymerization of olefin oxides and of olefin sulfides

Two new catalyst systems, sulfur–diethylzinc and 98% hydrogen peroxide–diethylzinc, have been investigated for polymerizing propylene oxide. The sulfur–diethylzinc catalyst system has a broad range of sulfur/zinc atomic ratio for polymerizing propylene oxide heterogeneously to high molecular weight materials in high yields. The highest polymer yield is obtained at the sulfur/zinc atomic ratio of 3–3.5. Like the water–diethylzinc system, the hydrogen peroxide–diethylzinc system has a narrow range of hydrogen peroxide/diethylzinc molar ratio in the vicinity of 0.57 for optimum polymer yield. Crystallinity measurements by x-ray diffraction of a few polymers prepared with these three catalyst systems showed that they are fairly similar in the extent of their crystallinity. A plot of the per cent of polymer insoluble in acetone against inherent viscosity of the original polymer also showed that the polymers prepared with sulfur–diethylzinc and hydrogen peroxide–diethylzinc catalyst systems have similar amounts of crystallinity. Data are given for the polymerizability of ethylene oxide, 1,2-butene oxide, styrene oxide, propylene sulfide, 1,2-butene sulfide, and a vulcanizable copolymer of propylene oxide and allyl glycidyl ether with the sulfur–diethylzinc catalyst system. The polymers from the olefin sulfides had lower inherent viscosities than the polymers from the corresponding olefin oxides. Aging of the sulfur–diethylzinc catalyst (S/Zn atomic ratio = 3.5) improved the yield of poly(propylene oxide). The yield was essentially unchanged when propylene oxide was polymerized in six different solvents. The formation of C₂H₅S_xZnSC₂H₅ and C₂H₅S_xZnS_yC₂H₅ (x and y are integers between 2 and 8) and possibly C₂H₅S_xZnC₂H₅ as the catalytically active species is postulated during the reaction of sulfur and diethylzinc.     

Copolymerization of propylene oxide with carbon dioxide catalyzed by zinc adipate

Copolymerization of carbon dioxide with propylene oxide in the presence of zinc adipate was studied. The effects of the temperature, nature of the solvent, and catalyst concentration on the molecular weight, molecular-weight distribution, and yields of the copolymer and propylene carbonate were examined. The structure of the polymer obtained was studied by ¹³N and ¹I NMR spectroscopy.     

Anionic bulk oligomerization of ethylene and propylene carbonate initiated by bisphenol‐A/base systems

When the bulk oligomerization of 1,3‐dioxolan‐2‐one (ethylene carbonate, EC) and 4‐methyl‐1,3‐dioxolan‐2‐one (propylene carbonate, PC) with the 2,2‐bis(4‐hydroxyphenyl)propane (bisphenol‐A, BPA)/base system (bases such as KHCO₃, K₂CO₃, KOH, Li₂CO₃, and t‐BuOK) was investigated at elevated temperature, significant differences were observed. Oligomerization of EC initiated by BPA/base readily takes place, but the oligomerization of PC is inhibited. The very first propylene carbonate/propylene oxide unit readily forms a phenolic ether bond with the functional groups of BPA phenolate, but the addition of the second monomer unit is rather slow. The oligomerization of EC yields symmetrical oligo(ethylene oxide) side chains. According to IR studies the oligomeric chains formed from PC with BPA contain not only ether but also carbonate bonds. The in situ step oligomerization of the BPA dipropoxylate was also identified by SEC, and a possible reaction mechanism is proposed. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 545–550, 1999     

Alternating copolymerization of propylene oxide and carbon dioxide with highly efficient and selective (salen)Co(III) catalysts: Effect of ligand and cocatalyst variation

Synthetic routes to a series of new (salen)CoX (salen = N,N′-bis(salicylidene)-1,2-diaminoalkane; X = Br or pentafluorobenzoate (OBzF₅)) species are described. Several of these complexes are active for the copolymerization of propylene oxide (PO) and CO₂, yielding regioregular poly(propylene carbonate) (PPC) without the generation of propylene carbonate byproduct. Variation of the salen ligand, as well as the inclusion of organic-based ionic or Lewis basic cocatalysts, has dramatic effects on the resultant (salen) CoX catalytic activity. Highly active (R,R)-(salen- 1 )CoOBzF₅ (salen- 1 = N,N′-bis(3,5- di-tert-butylsalicylidene)-1,2-diaminocyclohexane) catalysts with [Ph₄P]Cl or [PPN]Y ([PPN] = bis(triphenylphosphine)iminium; Y = Cl or OBzF₅) cocatalysts exhibited turnover frequencies up to 720 h⁻¹ for rac-PO/CO₂ copolymerization, yielding PPC with greater than 90% head-to-tail connectivity. Additionally, the (R,R)-(salen- 1 )CoOBzF₅/[PPN]Cl catalyst system demonstrated a k_rel of 9.7 for the enchainment of (S)- over (R)-PO when the copolymerization was carried out at low temperatures. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5182–5191, 2006     

Polymerization of alkylene oxides by dialkylzinc–lewis base systems

Dialkylzinc–Lewis base systems are found to be active catalysts for the polymerization of alkylene oxides. The diethylzinc–dimethyl sulfoxide system is especially effective in the preparation of high polymers of ethylene oxide and propylene oxide. Diethylzine does not react with dimethyl sulfoxide, but there is strong association between the compounds. The proton magnetic resonance spectrum of a poly(ethylene oxide) prepared by the catalyst system suggests that the n-butoxyl group is attached to the end of the polymer chain. Polymerization of ethylene oxide seems to be initiated by the ethyl–zinc bond. The active species of the system seems to be diethylzinc coordinated with dimethyl sulfoxide. The efficiency of the catalyst system for the formation of high molecular weight polymer is 10^?1?10^?2. The other part of the catalyst is responsible for the formation of low polymers.     

Organic Catalysis: Synthesis of Propylene Carbonate by the Carboxylation of Propylene Oxide in the Presence of Phenols and Fluorinated Alcohols

Phenol, polyphenols, as well as fluorinated alcohols actively catalyze the carboxylation of propylene oxide to form propylene carbonate in mild conditions (60°С, 7 at). The highest catalytic activity is characteristic of polyhydric phenols having neighbouring OH groups and alcohols with an enhanced acidity of OH protons. These catalysts in combination with tetrabutyammonium iodide exhibit activity at low concentrations (0.25 mol %) and ensure almost quantitative yields of propylene carbonate. The activity of the catalysts much increases with increasing ammonium salt amount (TOF up to 260), as well as temperature and initial СО₂ pressure (TON up to 370).     

High yield synthesis of biodegradable poly(propylene carbonate) from carbon dioxide and propylene oxide

A novel SalenCo^III (2,4‐dinitrophenoxy) (Salen = N,N'‐bis(3,5‐di‐tert‐butylsalicylidene)‐1,2‐cyclohexanediamino) and 1,10‐phenanthroline monohydrate catalyst system was designed and employed for the copolymerization of CO₂ and propylene oxide (PO). The perfectly alternating copolymerization of CO₂ and PO proceeds effectively under middle temperature and pressure to yield poly(propylene carbonate) with a high yield and a high number average molecular weight of polymer. The structure of polymer was characterized by the IR and NMR measurements. The perfectly alternating copolymer was confirmed. The MALDI‐TOF spectrum insinuates that the copolymerization of CO₂ and PO was initiated by H₂O. Copyright © 2016 John Wiley & Sons, Ltd.     

Copolymerization of propylene oxide and CO2 using achiral salophen Co(III) penta-florobenzoate as catalyst and tetrabutyl ammonium bromide as co-catalyst

Copolymerization of racemic propylene oxide with carbon dioxide is investigated in the presence of economically inexpensive and effective achiral salophenCo(III)X [salophen = N,N'-bis(3,5-di-tert-butylsalicylidene)-phenylenediimine, X = pentaflorobenzoate] catalyst and tetrabutyl ammonium bromide as co-catalyst. Effects of different variables like monomer to catalyst ratio, catalyst/co-catalyst ratio, temperature, pressure of CO₂ on molecular weight, yield and selectivity of poly(propylene carbonate) [PPC] have been investigated. The maximum M_w of 25.8 g/mol has been obtained at 15 bar and 50°C. All the samples were found to have excellent polydispersity near to 1.     

Hydrogen effects in propylene polymerization reactions with titanium‐based Ziegler–Natta catalysts. I. Chemical mechanism of catalyst activation

The hydrogen activation effect in propylene polymerization reactions with Ti‐based Ziegler–Natta catalysts is usually explained by hydrogenolysis of dormant active centers formed after secondary insertion of a propylene molecule into the growing polymer chain. This article proposes a different mechanism for the hydrogen activation effect due to hydrogenolysis of the Ti? iso‐C₃H₇ group. This group can be formed in two reactions: (1) after secondary propylene insertion into the Ti? H bond (which is generated after β‐hydrogen elimination in the growing polymer chain or after chain transfer with hydrogen), and (2) in the chain transfer with propylene if a propylene molecule is coordinated to the Ti atom in the secondary orientation. The Ti? CH(CH₃)₂ species is relatively stable, possibly because of the β‐agostic interaction between the H atom of one of its CH₃ groups and the Ti atom. The validity of this mechanism was demonstrated in a gas chromatography study of oligomers formed in ethylene/α‐olefin copolymerization reactions with δ‐TiCl₃/AlEt₃ and TiCl₄/dibutyl phthalate/MgCl₂–AlEt₃ catalysts. A quantitative analysis of gas chromatography data for ethylene/propylene co‐oligomers showed that the probability of secondary propylene insertion into the Ti? H bond was only 3–4 times lower than the probability of primary insertion. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1353–1365, 2002     

Isentropic partial molal compressibilities of alcohols in propylene carbonate at 25°C

The isentropic coefficients of compressibility of the homologous series of alcohols and diols R _n CH₂OH (n=2–6), CH₃CHOHR _n (n=1–5), 1,2-propanediol, 1,3- 1,4- and 2,3-butanediol, 1,5-pentanediol, and 1,7-heptanediol dissolved in propylene carbonate have been measured at 25°C. Isentropic partial molal compressibilities and group partial molal compressibilities at infinite dilution have been evaluated. The isentropic partial molal compressibilities of these alcohols and diols have been compared with the corresponding values in water. This comparison shows that the values in propylene carbonate are higher than in water by a factor of 10 due to an increased compressibility of the solvation sheath around nonpolar groups in PC.     

Dynamics of the NbCl5‐Catalyzed Cycloaddition of Propylene Oxide and CO2: Assessing the Dual Role of the Nucleophilic Co‐Catalysts

A mechanistic study on the synthesis of propylene carbonate (PC) from CO₂ and propylene oxide (PO) catalyzed by NbCl₅ and organic nucleophiles such as 4‐dimethylaminopyridine (DMAP) or tetra‐n‐butylammonium bromide (NBu₄Br) is reported. A combination of in situ spectroscopic techniques and kinetic studies has been used to provide detailed insight into the reaction mechanism, the formation of intermediates, and interactions between the reaction partners. The results of DFT calculations support the experimental observations and allow us to propose a mechanism for this reaction.     

N‐Heterocyclic Olefins as Organocatalysts for Polymerization: Preparation of Well‐Defined Poly(propylene oxide)

The metal‐free polymerization of propylene oxide (PO) using a special class of alkene—N‐heterocyclic olefins (NHOs)—as catalysts is described. Manipulation of the chemical structure of the NHO organocatalyst allows for the preparation of the poly(propylene oxide) in high yields with high turnover (TON>2000), which renders this the most active metal‐free system for the polymerization of PO reported to date. The resulting polyether displays predictable end groups, molar mass, and a low dispersity (?_M<1.09). NHOs with an unsaturated backbone are essential for polymerization to occur, while substitution at the exocyclic carbon atom has an impact on the reaction pathway and ensures the suppression of side reactions.     

Propylene polymerization with nickel–diimine complexes containing pseudohalides

DADNiX₂ nickel–diimine complexes [DAD = 2,6‐iPr₂? C₆H₃? N?C(Me)? C(Me)?N? 2,6‐iPr₂? C₆H₃] containing nonchelating pseudohalide ligands [X = isothiocyanate (NCS) for complex 1 and isoselenocyanate (NCSe) for complex 2 ] were synthesized, and the propylene polymerization with these complexes and also with the Br ligand (X = Br for complex 3 ) activated by methylaluminoxane (MAO) were investigated (systems 1 , 2 , and 3 /MAO). The polypropylenes obtained with systems 1 , 2 , and 3 were amorphous polymers and had high molecular weights and narrow molecular weight distributions. Catalyst system 1 showed a relatively high activity even at a low Al/Ni ratio and reached the maximum activity at the molar ratio of Al/Ni = 500, unlike system 3 . Increases in the reaction temperature and propylene pressure favored an increase in the catalytic activity. The spectra of polypropylenes looked like those of propylene–ethylene copolymers containing syndiotactic propylene and ethylene sequences. At the same temperature and pressure, system 2 presented the highest number of propylene sequences, and system 3 presented the lowest. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 458–466, 2006     

Partial molal volumes of alcohols in propylene carbonate at 25°C

The densities of the homologous series of alcohols and diols R_nCH₂OH (n=2–6), CH₃CHOHR_n (n=1–5), 1,2-propanediol, 1,3-1,4-, and 2,3-butanediol, 1,5-pentanediol, and 1,7-heptanediol dissolved in propylene carbonate have been measured at 25°C. The partial molal volumes at infinite dilution have been evaluated. Additivity of group molal volumes has been confirmed in propylene carbonate. The results have been discussed in relation to the same data in aqueous solution, and the scaled particle theory has been employed to calculate intrinsic volumes of the solutes.     

Asymmetric,regio‐ and stereo‐selective alternating copolymerization of CO2 and propylene oxide catalyzed by chiral chromium Salan complexes

Chiral chromium complexes of tetradentate N,N′‐disubstituted bis(aminophenoxide) (designated as Salan, a saturated version of Schiff‐base Salen ligand) in conjunction with an ionic quaternary ammonium salt can efficiently catalyze the copolymerization of CO₂ with racemic propylene oxide (rac‐PO) at mild conditions to selectively afford completely alternating poly(propylene carbonate) (PPC) with ～ 95% head‐to‐tail linkages and moderate enantioselectivity. These new catalyst systems predominantly exceed the previously much‐studied SalenCr(III) systems in catalytic activity, polymer enantioselectivity, and stereochemistry control. The chiral diamine backbone, sterically hindered substitute groups on the aromatic rings, and the presence of sp³‐hydridized amino donors and its N,N′‐disubstituted groups in chiral SalanCr(III) complexes all play significant roles in controlling polymer stereochemistry and enantioselectivity. Furthermore, a relationship between polycarbonate enantioselectivity and its head‐to‐tail linkages in relation to regioselective ring‐opening of the epoxide was also discussed on the basis of stereochemical studies of PPCs derived from the copolymerization of CO₂ with chiral PO at various conditions. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6102–6113, 2008     

Copolymerization of propylene and disubstituted diallylsilanes involving intramolecular cyclization with stereoselective zirconocene catalysts

The copolymerization of propylene and disubstituted diallylsilanes [(CH₂ ?CH? CH₂? )₂R₂Si (R = CH₃ or C₆H₅)] was investigated with isoselective and syndioselective zirconocene catalysts with methylaluminoxane as a cocatalyst. The syndioselective catalyst showed a higher reactivity for disubstituted diallylsilanes than the isoselective catalysts. Diallyldimethylsilane was incorporated into the polymer chain via cyclization insertion preferentially and formed 3,5‐disubstituted dimethylsilacyclohexane units in the polypropylene main chain. In the copolymerization with diallyldiphenylsilane, diallyldiphenylsilane was copolymerized via both cyclization insertion and 1,2‐insertion, which formed a pendant allyl group. The structures of isolated silacyclohexane units, determined by ¹³C NMR and distortionless enhancement by polarization transfer spectroscopy, proved that the 1,2‐insertion of diallylsilanes proceeded with enantiomorphic site control; however, the diastereoselectivity of the cyclization reaction was independent of the stereoselectivity of the catalysts used, and cis‐silacyclohexane units were mainly formed. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6083–6093, 2006     

KI与无机铵盐催化CO2与环氧丙烷合成碳酸丙烯酯

以无毒、合成简单、廉价的无机铵盐(氨基甲酸铵、碳酸氢铵、碳酸铵等)为助催化剂, 研究其对卤化钾(KCl、KBr、KI)催化CO₂与环氧丙烷合成碳酸丙烯酯(PC)的影响. 结果表明, 卤化钾与无机铵盐显示出很好的协同催化效应. 其中以氨基甲酸铵为助催化剂, KI为主催化剂时, 催化合成PC的效果最好. 同时考察了催化剂用量、反应温度、CO₂初始压力、PC的预加入量、反应时间等因素对反应的影响. 在优化条件下, PC收率大于99%.     

Synthesis and polymerization behavior of novel C 1 and C s titanium ansa‐cyclopentadienyl‐amido catalysts for ethylene and propylene polymerization

Four titanium ansa‐cyclopentadienyl‐amido complexes of the general formula [C₅H₃RMe₂SiN(2,6‐Me₂C₆H₃)]TiX₂(R = H,Me,Bz,^tBu;X = NMe₂ or Cl) have been synthesized. The complexes polymerize both ethylene and propylene in the presence of methylaluminoxane or Ph₃CB(C₆F₅)₄–triisobutylaluminum and were most active at lower temperatures. In general, the smaller the substituent on the cyclopentadienyl group, the more active the catalyst. The catalysts were found to be poorly stereoselective for the polymerization of polypropylene, with the tertiary‐butyl substituted catalyst giving a polymer with the greatest [mmmm] (14.2%). The structure of [C₅H₄Me₂SiN(2,6‐Me₂C₆H₃)] Ti(NMe₂)₂ was determined by X‐ray diffraction. The complex crystallizes in the monoclinic system space group P2₁/n, with a = 16.437(2), b = 8.652(3), c = 16.494(4),β = 117.54(2) and Z = 4. Copyright © 2002 John Wiley & Sons, Ltd.     

13C NMR determination of the microstructure of polypropylene obtained with the DADNi(NCS)2/methylaluminoxane catalyst system

A complete ¹³C NMR characterization of a polymer synthesized with a new Ni‐diimine complex [DADNi(NCS)₂, where DAD = 2,6‐iPr? C₆H₃? N?C(Me)? C(Me)? N? 2,6‐iPr? C₆H₃] activated by methylaluminoxane by homopolymerization of propylene is presented. The amorphous material was made up mainly of blocks of syndiotactic polypropylene and ethylene–propylene copolymer. Some degree of propylene inversion (<1.2 mol %) and of long isobutyl and 2‐methyl hexyl branching (<1 mol %) were assigned and quantified. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2171–2178, 2004     

Copolymerization of carbon dioxide and propylene oxide using an aluminum porphyrin system and its components

The catalytic activities of tetraphenylporphinatoaluminum chloride (TPPAlCl) and its propylene oxide adduct (TPPAl(PO)₂Cl) were investigated in detail together with a quarternary salt Et₄NBr for the copolymerization of carbon dioxide and propylene oxide. In addition, for the components and starting raw materials of the catalyst systems, catalytic activities were examined for the copolymerization. The TPPAlCl catalyst delivered oligomers containing ether linkages to a large extent, regardless of its PO adduction. And cyclic propylene carbonate, as byproduct, was formed in a very small portion. Using the TPPAlCl coupled with Et₄NBr as a catalyst system, the formation of ether linkages was reduced significantly in the copolymerization; however, the obtained oligomer still contained ether linkages of 25.0 mol % in the backbone. On the other hand, the formation of cyclic carbonate was increased to 22.4 mol % relative to the oligomer product. The results indicate that the salt, which was coupled with the TPPAlCl catalyst, plays a key role in reducing the formation of ether linkage in the oligomer and, however, in enhancing the formation of cyclic carbonate. Similar results were obtained for the copolymerization catalyzed by the TPPAl(PO)₂Cl/Et₄NBr system. That is, the formation of ether linkages was not restricted further by the PO adduction of the TPPAlCl component in the catalyst system. Only oligomers with a relatively high molecular weight were produced. This indicates that the PO adduction of the TPPAlCl component contributes highly to the initiation and propagation step in the oligomerization, consequently leading to a relatively high molecular weight oligomer. In contrast, the Et₄NBr, as well as the Et₂AlCl, produced only cyclic carbonate in a very low yield. Furthermore, tetraphenylporphine exhibited no catalytic activity, regardless of using together with Et₄NBr. On the other hand, the Et₂AlCl coupled with Et₄NBr provided a low molecular weight oligomer having ether linkages of 92.3 mol % in addition to the cyclic carbonate. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3329–3336, 1999