Living cationic polymerisation of styrene in an ionic liquid

For the first time, living cationic polymerisation of styrene has been carried out in room temperature ionic liquids under mild reaction conditions and using mild acid catalysts (e.g. organoborate acids) to obtain polymers of narrow polydispersity.     

Cationic polymerization of styrene involving ionization of the C?Cl bond in ionic liquid/SO2 mixture

There has been a recent upsurge in interest in use of ionic liquids as reaction media for various chemical processes. Until recently, ionic liquids were considered as highly polar solvents. Our earlier investigation indicated that cationic polymerization of styrene initiated by aryl (alkyl) chlorides in ionic liquids may proceed even in the absence of coinitiator (Lewis acid). Polymerization, however, did not conform to controlled polymerization scheme. More recently, it has been claimed that ionic liquids are not as polar as it was previously assumed. Independently, high solubility of sulfur dioxide in ionic liquids was noticed. As sulfur dioxide displays a high ionizing power toward organic halides, we applied ionic liquid/sulfur dioxide mixture as a solvent in cationic polymerization of styrene initiated by aryl (alkyl) chlorides. Results show that in this reaction medium ionization of the C? Cl bond is facilitated, and the contribution of chain transfer reaction can be reduced as compared with polymerization in ionic liquid alone. Ionization of the C? Cl bond, however, is still not sufficiently fast to ensure conditions of controlled polymerization. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5251–5257, 2009     

Polymerization Processes in Ionic Liquids. Cationic Polymerization of Styrene

There is an increasing interest in using ionic liquids as solvents for polymerization processes. Most published data deals with controlled radical polymerization. It has been shown that ionic liquids offer several advantages for conducting Atom Transfer Radical Polymerization (ATRP), such as good solubility of catalyst and improved k_p/k_t ratio. Ionic liquids are highly polar therefore they seem to be suitable solvents for conducting also ionic polymerization processes. In our preliminary communication we reported on cationic polymerization of styrene initiated by R-Cl/TiCl₄ system in ionic liquid. To clarify the mechanism of this process, racemization of optically active 1-phenylethyl choride (initiator and the model of dormant species) was studied and it was shown that in ionic liquid racemization proceeds even in the absence of coinitiator (TiCl₄). Because racemization proceeds through ionization of C Cl bond, this explains the cationic polymerization of styrene initiated by R-Cl alone (in the absence of coinitiator). Chain transfer, however, cannot be eliminated, therefore polymerization is not controlled.     

Biphasic hydroformylation in ionic liquids: interaction between phosphane ligands and imidazolium triflate, toward an asymmetric process

Biphasic hydroformylation of dec-1-ene and styrene, at commercially competitive rates, can be successfully performed in imidazolium triflate ionic liquids; the ionic liquid network forms 'inclusion complexes' with the phosphane ligands used to modify the rhodium catalyst.     

Half-titanocenes for precise olefin polymerisation: effects of ligand substituents and some mechanistic aspects

Selected examples concerning effects of both cyclopentadienyl fragment (Cp') and anionic donor ligand (Y) in nonbridged modified half-titanocenes of the type, Cp'TiX(2)(Y) (X = halogen, alkyl), as new type of olefin polymerisation catalysts have been reviewed. These complexes displayed unique characteristics not only for ethylene (co)polymerisation but also for syndiospecific styrene polymerisation, ethylene/styrene copolymerisation; precise fine tuning of the ligand substituents plays an important role for the successful (co)polymerisation; a different mechanistic consideration for the syndiospecific styrene polymerisation, which can explain the copolymerisation behaviour in this catalysis, has also been introduced.     

The catalytic performance study of polymerized ionic liquid synthesized in different conditions on alkylation of o‐Xylene with styrene

In this work, a series of novel acidic polymerized ionic liquids were used as heterogeneous catalyst for alkylation of o‐Xylene with styrene. And the effect of the amount of initiator and the type of acid used for ion exchange on catalyst structure and the catalytic performance of catalysts for alkylation were studied thoroughly. The experiment results show: when the percentage of the amount of initiator in the total material is 3%, the polymerized ionic liquid catalyst MPM‐SO₃H‐[C₃V][SO₃CF₃] has the most uniform with a specific surface area of 97.30 m²/g and a pore volume of 0.35 cm³/g. Benefiting from the unique structure features, MPM‐SO₃H‐[C₃V][SO₃CF₃] manifested an excellent catalytic performance for alkylation of o‐Xylene with styrene, along with the conversion of styrene was 96.8% and the yield of 1‐Phenyl‐1‐ortho‐xylene ethane was 94.7%. Therefore, this work provides a novel reference to the synthesis of polymerized ionic liquids and clearly explains the advantage of novel acidic polymerized ionic liquids on alkylation.     

Biphasic ethylene polymerisation using 1-n-alkyl-3-methylimidazolium tetrachloroaluminate ionic liquid as a medium of the Cp2TiCl2 titanocene catalyst

A systematic analysis was performed on a series of 1-n-alkyl-3-methylimidazolium tetrachloroaluminates (where alkyl = ethyl, butyl, hexyl, and octyl), applied as a medium of the Cp₂TiCl₂ titanocene catalyst, to evaluate the influence of the physical properties of the ionic liquids on the polymerisation reaction carried out in the biphasic ionic liquid/hexane mode. Two alkylaluminium compounds, AlEtCl₂ and AlEt₂Cl, were used as activators. The influence of the activator/catalyst molar ratio on the performance of the ethylene polymerisation was determined for each ionic liquid studied. The best results were obtained using 1-n-octyl-3-methylimidazolium tetrachloroaluminate. For the titanocene catalyst immobilised in the ionic liquid, AlEtCl₂ turned out to be a better activator than AlEt₂Cl in our studies. The properties of the polyethylene product have also been presented.     

Asymmetric cyclopropanation in ionic liquids promoted by dicopper complexes of ditopic ligands

The use of ionic liquid phases to immobilise dicopper complexes of ditopic chiral ligands bearing bis(oxazoline) moieties has been explored in the enantioselective cyclopropanation reaction of styrene with ethyl diazoacetate. The recoverability of these catalytic phases has been studied using different ionic liquids and ligands. The origin of the ionic liquid is determinant both for the catalytic results and the reusability of the system.     

Regioselectivity of styrene carbonylation in the presence of palladium(II) complexes

The influence of a catalyst on regioselectivity of styrene carbonylation in ionic liquids catalyzed by palladium(II) complexes was studied. The mechanism of the migration insertion of styrene at the palladium-hydrogen bond determining the regioselectrivity of the whole reaction, which is treated as electrophilic addition to the multiple bond of styrene, was studied. A study of the structure of intermediate complexes formed at this stage was performed using the B3LYP method of density functional theory.     

Effect of ligand substituents in olefin polymerisation by half-sandwich titanium complexes containing monoanionic iminoimidazolidide ligands-MAO catalyst systems

Various half-sandwich titanium complexes containing iminoimidazolidide ligands, CpTiCl(2)[1,3-R(2)(CH(2)N)(2)C=N] (1a-d) [R = Ph (a), 2,6-Me(2)C(6)H(3) (b), cyclohexyl (c), (t)Bu (d)], have been employed as the catalyst precursors for ethylene polymerisation, syndiospecific styrene polymerisation, and copolymerisation of ethylene with 1-hexene in the presence of MAO cocatalyst; 1d showed the highest catalytic activity for ethylene polymerisation whereas 1b showed the highest activity for syndiospecific styrene polymerisation.     

Reversible addition-fragmentation chain transfer polymerization of methacrylate, acrylate and styrene monomers in 1-alkyl-3-methylimidazolium hexfluorophosphate

1-alkyl-3-methylimidazolium hexfluorophosphate ([C_x][PF₆], where x=4, 6-8) is used as solvent for the polymerisation of methyl methacrylate, methyl acrylate and styrene by the reversible addition-fragmentation chain transfer process. In the case of styrene, the insolubility of the polymer in ionic liquid stops the polymerization at an early stage. The acrylate and methacrylate polymerizations lead to products with molecular weights close to the theoretical ones and polydispersity indexes lower than 1.3. The polymerizations are shown to be living by chain extension of the products formed in ionic liquid. In the case of the methyl methacrylate, the kinetics of the polymerizations are followed and the molecular weight of the polymer is shown to increase linearly with the conversion, as expected for a living polymerization.     

Enantioselective cyclopropanation reactions in ionic liquids

The benchmark enantioselective cyclopropanation of styrene with ethyl diazoacetate, promoted by two different bis(oxazoline)-copper complexes, is studied in three ionic liquids. The nature of both the anion and cation influence the behaviour of the catalysts, which can be recovered and re-used.     

New chiral (salen)manganese(III) systems for asymmetric epoxidation of styrene

Highly enantioselelctive and repeatable epoxidation of styrene was performed by using new chiral (salen)Mn(III) catalysts, which were derived from the initial immobilization of a homogeneous (salen)Mn(III) complex on solid carriers and subsequent dispersion into ionic liquids. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Markownikoff and anti-Markownikoff hydroamination with palladium catalysts immobilized in thin films of silica supported ionic liquids

The concept of immobilising organometallic complexes in a thin film of supported ionic liquids was utilised to synthesise novel bi-functional catalysts combining soft Lewis acidic and strong Br?nsted acidic functions; the materials showed exceptional catalytic activity for the addition of aniline to styrene, providing the Markownikoff product under kinetically controlled conditions and mainly the anti-Markownikoff product in the thermodynamic regime.     

Polymerisation in supported bilayers

The intercalation of the twin-tailed amphiphilic dioctadecyldimethylammonium (DODA) ions in smectite clay minerals provides a well-defined supported bilayer system. Polymerisation of styrene in these robust model bilayers allows one to focus on the effect of the constrained medium on the polymerisation process and the polymer. Small-angle X-ray scattering analysis and differential scanning calorimetry data indicated that the polymerisation of styrene in DODA–montmorillonite leads to phase separation between polystyrene and the surfactant matrix. Received: 14 April 2000/Accepted: 19 June 2000     

The effect of 4-vinylcyclohexene on the degradation of polystyrene and on the polymerisation of styrene

It has previously been postulated that the inhibition of polystyrene degradation observed in the initial stages of the isothermal degradation of polystyrene-polybutadiene blends is partly due to reaction of polystyryl radicals with 4-vinylcyclohexene (4VCH) evolved from the polybutadiene. This hypothesis has been tested by examining the effect of small amounts of 4VCH on polystyrene degradation and on the free radical polymerisation of styrene. The results provide support for the hypothesis: there is an induction period in the degradation and the polymerisation is retarded. From molecular weight measurements on polymers made in the presence of various amounts of 4VCH, a chain transfer constant in styrene polymerisation at 60°C of 117 × 10^?5 has been calculated.     

离子液体中1—苯基—1—二甲苯基乙烷的清洁催化合成

研究了在1-甲基-3-烷基咪唑、1-烷基吡啶及盐酸三甲胺季胺盐与无水AlCl3组成的室温离子液体系中,二甲苯与苯乙烯的烷基化反应制1-苯基-1-二甲苯基乙烷及其衍生物。对离子液体催化剂量和反应条件对产物组成级副产物数量的影响进行了考察。结果表明,离子液反应体系中存在着烷基化与异构化两个不同的反应阶段。该体系具有很好的催化性能,反应可在常温下进行,且产物易于分离、纯度高,催化剂可以重复使用。     

Tuning the active species from syndiospecific styrene polymerisation to ethylene/styrene copolymerisation by (aryloxo)(cyclopentadienyl)titanium complexes-MAO catalysts

Exclusive formation of poly(ethylene-co-styrene)s were observed by introduction of ethylene into the solution of syndiospecific styrene polymerisation using Cp'TiCl(2)(O-2,6-(i)Pr(2)C(6)H(3)) (Cp' = 1,2,4-Me(3)C(5)H(2), tert-BuC(5)H(4))-MAO catalysts without by-production of syndiotactic polystyrene, whereas the styrene polymerisation did not proceed when ethylene was removed from the reaction mixture of ethylene/styrene copolymerisation.     

Polymerisation in lyotropic liquid-crystalline phases of dioctadecyldimethylammonium bromide

The polymerisation of styrene in lyotropic liquid-crystalline (LC) phases of dioctadecyldimethylammonium bromide (DODAB) in water is explored. Amphiphile concentrations between 20 and 50 wt % are employed. The study is set out as a model study for polymerisation reactions in nonstabilised, nonfunctional bilayer systems. X-ray characterisation was used to assess the phase behaviour of the lyotropic mesophases before, during and after polymerisation. The DODAB/water system forms the lamellar phase within the concentration range considered. Addition of styrene to the lamellar phase of DODAB at an equimolar ratio induces a phase shift to a bicontinuous cubic phase at elevated temperatures near the phase-transition temperature. Upon polymerisation within this cubic phase, the phase structure is maintained if the system is kept at constant temperature; however, if the polymer/amphiphile phase is cooled, the lamellar phase, being typical of the DODAB/water system, is restored. It is concluded that, as a result of phase separation between the polymer and the amphiphile phase, the polymerisation in lyotropic LC phases does not provide a stable copy of the templating amphiphile phase. This is in analogy to the observations for polymerisations in other lyotropic phases. Received: 16 March 2000 Accepted: 1 July 2000     

The dispersion polymerization of unsaturated monomers initiated by the macromonomeric initiator

The dispersion polymerizations of styrene (St) and methyl methacrylate (MMA) initiated by poly(oxyethylene) macroinimer (PEO-MIM) in ethanol/water were investigated at 50, 60 and 80°C. The polymerisation rate vs. conversion dependence was described by with a maxim at the beginning of polymerisation. Polymerization was faster with MMA than with St. The limiting conversion was inversely proportional to temperature and was much more pronounced with St. The rate of polymerization increased with temperature. The overall initial activation energy increased with conversion and reached value ca. 25 kJ.mol⁻¹ for MMA and 50 kJ.mol⁻¹ for styrene at ca. 60% conversion. The particle size was observed to decrease with increasing the macroinimer concentration. The polymer dispersions were unstable and a large amount of coagulum appeared during the polymerisation especially in the styrene-containing reaction system.