Cationic Polymerization Of Isobutylene Research Articles

Highly reactive polyisobutylene through cationic polymerization of isobutylene

Highly reactive polyisobutylene through cationic polymerization of isobutylene

Visible-Light-Induced Cationic Polymerization of Isobutylene: A Route toward the Synthesis of End-Functional Polyisobutylene.

The visible-light-induced cationic polymerization of isobutylene with a dimanganese decacarbonyl (Mn2(CO)10)/diphenyl iodonium hexafluorophosphate (Ph2I+PF6-) photoinitiating system in a CH2Cl2/n-hexane mixture at -30 °C was reported. It was shown that polymerization is initiated by chloromethylisobutyl carbocations generated by the oxidation of chloromethylisobutyl radicals by Ph2I+PF6-. The latter are formed via chlorine abstraction from solvent (CH2Cl2) by MnCO5· radicals, which are generated by the photoinduced decomposition of Mn2(CO)10, followed by single isobutylene addition. This initiating system allowed us to synthesize valuable low molecular weight polyisobutylene with a relatively low polydispersity (Mn = 2000-3000 g mol-1; Đ < 1.7) and high content of exo-olefin end groups (up to 90%). The molecular weight of polyisobutylenes could be easily controlled in the range from 2000 to 12000 g mol-1 by changing the diphenyl iodonium salt concentration. Poly(β-pinene) with Mn = 5000 g mol-1 and Đ ∼ 2.0 was successfully synthesized using the same photoinitiating system.

Synthesis of high molecular weight polyisobutylene with Al(C6F5)3-based initiating systems under mild conditions

We report here by using a binary initiating system containing a sterically bulky Lewis super acid Al(C6F5)3 together with cumyl chloride (CumCl), the cationic polymerization of isobutylene was realized at temperatures varying from −60 °C to 15 °C in a non-halogenated solvent to afford polymers with medium molecular weights from 0.9 × 104 to 14.8 × 104 g·mol−1. Moreover, addition of EDs (EDs = OPh2, SPh2 and NPh3) to the above system generated ternary systems, leading to obvious improvement of the catalytic performances. Among these systems, Al-CumCl-OPh2 was mostly efficient to transfer up to 20,000 equiv. IB into PIBs with high molecular weights up to 35.5 × 104 g·mol−1 at −40 °C. The activation energies (Ep) for the polymerization degree with different initiating systems were determined, suggesting that the molecular weight of PIB was strongly dependent on the polymerization temperature.

Aspects of the Synthesis of Poly(styrene-block-isobutylene-block-styrene) by TiCl4-Co-initiated Cationic Polymerization in Open Conditions

The cationic polymerization of isobutylene and its block copolymerization with styrene using DiCumCl/TiCl4/2,6-lutidine initiating system has been studied in open conditions. It was shown that a higher concentration of proton trap is required in open conditions as compared to the glove box technique in order to have good control over molecular weight and polydispersity. Polyisobutylenes with Mn ≤ 50,000 g mol−1 and low polydispersity (Đ ≤ 1.2) were prepared at [Lu] = 12 mM. The synthesis of poly(styrene-block-isobutylene-block-styrene) triblock copolymer (SIBS) in open conditions required the addition of proton trap into two steps, half at the beginning of the reaction and the second half together with styrene. Following this protocol, a series of triblock copolymers with different length of central polyisobutylene block (from Mn = 20,000 g mol−1 to 50,000 g mol−1) and side polystyrene blocks (Mn = 4000 g mol−1–9000 g mol−1) with low polydispersity (Đ ≤ 1.25) were synthesized. High molecular SIBS (Mn &gt; 50,000 g mol−1) with low polydispersity (Đ &lt; 1.3) containing longer polystyrene blocks (Mn &gt; 6000 g mol−1) demonstrated higher tensile strength (~13.5 MPa).

BROMINATED ISOBUTYLENE-CO-PARAMETHYLSTYRENE WITH SUPERIOR IMPERMEABILITY FOR TIRE INNERLINER APPLICATIONS

ABSTRACT Isobutylene elastomers are of great commercial importance in tire applications because of their notable low gas permeability properties, owing to their efficient molecular packing. Brominated isobutylene-co-para-methylstyrene (BIMSM) elastomers are a special class of isobutylene elastomers synthesized by random cationic polymerization of isobutylene and para-methylstyrene (pMS), followed by a selective bromination of the methyl group of the pMS units. BIMSM elastomer, commercially known as Exxpro™ specialty elastomer, exhibits superior heat resistance and aging properties and is much more resistant to chemicals and ozone than butyl- or halobutyl polymers because of its fully saturated backbone structure. The permeability properties of BIMSM elastomers can be tuned by the level of pMS comonomer present in the polymer chain. The pMS comonomer increases the glass transition temperature of the copolymer, and polymers with very low gas permeability needed for demanding tire air retention applications can be produced by suitably selecting the pMS content. A single type of benzylic bromide, but with a versatile functional group, allows for precise control of vulcanization chemistry, potential for other chemical transformations to achieve other reactive groups, and grafting reactions. We present the new material developments to meet the growing market demands and requirements for low maintenance, low inflation pressure loss rate tires and tires for connected autonomous shared electric vehicles.

Recent advances in catalytic chain transfer polymerization of isobutylene: a review.

This review presents the development of highly reactive polyisobutylene (HRPIB), a major commercial intermediate toward fuel and lubricant additives. Recent years have witnessed very substantial advances in the catalytic chain transfer polymerization (CCTP) of isobutylene/industrial Raffinate-1 (C4 Raffinate) to produce HRPIB, particularly in nonpolar solvents at elevated temperatures. The main subjects of this review are cationic polymerization of isobutylene, progress in HRPIB research and existing challenges, and recent advances of CCTP. New initiating/catalyst systems based on ionic liquids with Lewis acids are detailed, and this approach may open new views in the synthesis of HRPIB. Some current developments in CCTP of industrial Raffinate-1 and mechanistic studies are also described. This review strongly supports that the hydrocarbon soluble Lewis acid·ether (LA·ether) complex catalyzed CCTP will become the most popular technique for preparing HRPIB and could replace the traditional BF3 catalyzed industrial method.

Synthesis, characterization and end-functionalization of a novel telechelic star: styrene hexamer core carrying polyisobutylene arms fitted with allyl termini

The synthesis and characterization of a new star consisting of a hard styrene hexamer (St6) core of which emanate long soft polyisobutylene (PIB) arms and fitted with allyl (A) termini is documented. The synthesis was accomplished by a core-first strategy in two steps: (a) creating the core by living anionic hexamerization of 3-(2-methoxyisopropyl)styrene in essentially quantitative conversion with nearly targeted molar mass (Mn = 1450 g/mol) of very low dispersity (1.06), and (b) using this hexamer to produce in one pot PIB-A arms by living cationic polymerization of isobutylene (> 99% conversion), and terminating with allyltrimethylsilane. This is the first example of a star synthesis by anionic-to-cationic site transformation. Intermediates and final products were characterized by 1H NMR spectroscopy and GPC according to which the star had ~ 4.61 arms. The star was end-functionalized by thiol-ene clicking with furfuryl mercaptan (~ 85% yield) for the preparation of a furan-telechelic star.

Facile synthesis of medium molecular weight polyisobutylene with remarkable efficiency employing the complexed BF3·EtOH/TiCl4·H2O initiating system

In this work, a novel complexed catalyst system consisting of BF3·EtOH/TiCl4·H2O was synthesized and systemically investigated. It revealed that notable synergistic effect could be observed for the complexed catalyst in the cationic polymerization of isobutylene (IB), reflected by the much higher activity of the complexed one (>5.4 × 103 kgPIB·mol−1(BF3 + TiCl4)·h−1) than those of BF3·EtOH (<2.6 × 103 kgPIB·mol−1BF3·h−1) and TiCl4·H2O (<10 kgPIB·mol−1TiCl4·h−1) under the optimized reaction conditions. Thus with lower than 3 mmol·L−1 Lewis acids (BF3 + TiCl4), reasonable monomer conversion higher than 80% could be achieved at high monomer concentration (4–6 mol·L−1) in 15 min with the complexed catalyst. Moreover, polyisobutylene (PIB) with adjustable Mn = 20,000–60,000 g·mol−1 and relatively narrow molecular weight distribution (MWD) = 2–4 was commonly produced with the complexed catalyst at reaction temperature from −30 to −60 °C. Generally, this complexed catalyst system exhibits remarkable efficiency for IB polymerization, and is endowed with possible industrial relevance for the synthesis of medium molecular weight polyisobutylene (MPIB, Mn = 10,000–100,000 g·mol−1).

Cationic Polymerization of Isobutylene and C4 Mixed Feed Using Complexes of Lewis Acids with Ethers: A Comparative Study

The cationic polymerization of C4 mixed feed and isobutylene co-initiated by AlCl3×OiPt2, iBuAlCl2×nOiPr2, and [emim]Cl-FeCl3×nOiPr2 ([emim]Cl: 1-ethyl-3-methylimidazolium chloride) has been investigated. AlCl3×OiPr2 co-initiated cationic polymerization of C4 mixed feed proceeds at a lower rate than polymerization of isobutylene affording polymers with higher molecular weight. Complexes of iBuAlCl2 with diisopropyl ether of different compositions are more suitable co-initiators than AlCl3×OiPr2 for the synthesis of highly reactive polyisobutylene (HR PIB) from C4 mixed feed due to their higher activity in the polymerization as well as possibility to prepare polyisobutylenes with lower molecular weight and higher content of exo-olefin end groups. However, iBuAlCl2 needs activating via addition of external water (initiator) and/or interaction with salts hydrates in order to increase the reaction rate and the saturated monomer conversion. [Emim]Cl-FeCl3/iPr2O is a quite promising catalyst for the preparation of HR PIB with high exo-olefin end group content (> 80%) and relatively low polydispersity (Mw/Mn < 2.8) via cationic polymerization of C4 mixed feed. The sonication of reaction mixture in case of using [emim]Cl-FeCl3 allowed increasing the reaction rate and decreasing the molecular weight.

Alkoxy aluminum chlorides in the cationic polymerization of isobutylene: a co-initiator, carbocation stabilizer and chain-transfer agent

Alkoxy aluminum chlorides are efficient catalysts for the preparation of well-defined exo-olefin terminated PIBs of low (Mn ∼ 1000 g mol−1) to medium (Mn up to 50 000 g mol−1) molecular weight under mild experimental conditions.

Synthesis of highly reactive polyisobutylenesviacationic polymerization in ionic liquids: characteristics and mechanism

The cationic polymerization of isobutylene (IB) was systematically studied in a 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim][PF6]) ionic liquid at −10 °C.

Acidic imidazole-based ionic liquids in the presence of diisopropyl ether as catalysts for the synthesis of highly reactive polyisobutylene: Effect of ionic liquid nature, catalyst aging, and sonication

A number of imidazole-based acidic (χ(LA)≥0.6) ionic liquids (RmimCl-LA, where R = Et or Bu, LA = AlCl3, AlBr3, iBuAlCl2, FeCl3, GaCl3, and BBr3) has been synthesized and their activity in cationic polymerization of isobutylene has been assessed. Among different ionic liquids tested here, emimCl-AlCl3, emimCl-FeCl3 and emimCl-GaCl3 showed the best results in terms of monomer conversion, exo-olefin end group content and polydispersity. It was shown that reaction rate depended strongly on the rate of partial hydrolysis of corresponding ionic liquid and increased in the following order: emimCl-FeCl3<emimCl-GaCl3<emimCl-AlCl3. It was demonstrated that emimCl-FeCl3 is the most promising catalyst for the synthesis of HR PIB with desired low molecular weight (Mn < 2500 g mol−1) and polydispersity (Mw/Mn < 2.5) and high content of exo-olefin end groups (>85%). However, due to poor dispergation of emimCl-FeCl3 in n-hexane as well as its high stability toward hydrolysis, the catalyst aging and/or sonication of reaction mixture is required in order to provide acceptable polymerization rate.

Cationic Copolymerization and Multicomponent Polymerization of Isobutylene with C4 Olefins

Cationic polymerization of isobutylene (IB) in the presence of other C4 olefins, 1-butene (B1), cis-2-butene (C2B), and 1,3-butadiene (BD) using the ethylaluminum dichloride (EADC)·bis(2-chloroethyl) ether (CEE) complex in conjunction with tert-butyl chloride (t-BuCl) as initiator in hexanes at 0 °C has been investigated. The reactivity ratio of IB rIB = 1100 was determined for copolymerization of IB and B1 at low conversions, using product compositions obtained from inverse gated 13C NMR analysis. The reactivity ratio of B1 rB1 = 1 was deduced from theoretical considerations. At low B1 incorporation levels, exo-olefin contents remained high in the copolymers, and the molecular weights were virtually unchanged relative to the experiments with IB alone [Banerjee, S.; Macromolecules 2015, 48, 5474]. Close to linear first-order plots of ln{[M]0/[M]} versus time were obtained ([M]0 and [M] are IB concentrations at time t = 0 and t, respectively) when the copolymerization was carried out with [IB] > 2 M. This ...

Cationic polymerization of isobutylene in toluene: toward well-defined exo-olefin terminated medium molecular weight polyisobutylenes under mild conditions

Medium molecular weight polyisobutylenes (∼35 000 g mol−1) with exo-olefin end groups (&gt;80%) can be obtained by cationic polymerization of isobutylene in toluene using iBu2AlCl or iBuAlCl2·nOR2 (n = 0.6–0.8) as co-initiators.

ChemInform Abstract: Recent Progress in the Lewis Acid Co‐Initiated Cationic Polymerization of Isobutylene and 1,3‐Dienes

AbstractReview: [recent approaches towards the synthesis of exo‐olefin terminated polyisobutylenes and well‐defined poly(1‐3‐diene)s; 94 refs.

Synthesis and Self‐Assembly of Polyisobutylene Based Thermoresponsive Diblock Copolymers via Combination of Cationic and RAFT Polymerizations

SummaryBy the combination of living carbocationic and reversible addition‐fragmentation chain transfer (RAFT) polymerizations, a series of well‐defined amphiphilic diblock copolymers composed of polyisobutylene (PIB) and poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA) were successfully synthesized. First, cationic polymerization of isobutylene (IB) followed by chain end functionalization gave PIB‐macro chain transfer agent, which was subsequently used for block copolymerization with oligo(ethylene glycol) methyl ether methacrylate (OEGMA). Gel permeation chromatography (GPC) confirmed successful and efficient block copolymerzation. The thermoresponsive behaviour of block copolymer aqueous solutions was determined by UV‐vis spectroscopy. These block copolymers self‐assembled into spherical core‐shell nanostructures in an aqueous solution as evidenced by dynamic light scattering (DLS) and scanning electron microscope (SEM).

Cationic polymerization of isobutylene by complexes of alkylaluminum dichlorides with diisopropyl ether: An activating effect of water

The RAlCl2 × OiPr2-co-initiated (R = iBu or Et) cationic polymerization of isobutylene in the presence of externally added water (0.016–0.1 mM) in nonpolar n-hexane at 10 °C and high monomer concentration ([IB] = 5.8 M) has been investigated. It was shown that the sequence of H2O introduction into the system had the crucial effect on the polymerization rate, saturated monomer conversion, and, to a lesser extent, the content of exo-olefin end groups. Particularly, the highest polymerization rate (>70% of monomer conversion in 10 min) and acceptable exo-olefin end groups content (∼83%) were observed when iBuAlCl2 × 0.8OiPr2 reacted with suspended in n-hexane H2O before the monomer addition. Better functionality can be obtained when H2O is introduced into the system in the course of the polymerization (after 3–10 min since the initiation of reaction). Under these conditions, highly reactive polyisobutylenes (exo-olefin content is 86–89%) with desired low molecular weight (Mn = 1000–2000 g mol−1) in a high yield (75–90% of monomer conversion in 20 min) were readily synthesized. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 2386–2393

Olefin Isomerization and Hydrosilylation Catalysis by Lewis Acidic Organofluorophosphonium Salts

Organofluorophosphonium salts of the formula [(C6F5)(3-x)Ph(x)PF][B(C6F5)4] (x = 0, 1) exhibit Lewis acidity derived from a low-lying σ* orbital at P opposite F. This acidity is evidenced by the reactions of these salts with olefins, which catalyze the rapid isomerization of 1-hexene to 2-hexene, the cationic polymerization of isobutylene, and the Friedel-Crafts-type dimerization of 1,1-diphenylethylene. In the presence of hydrosilanes, olefins and alkynes undergo efficient hydrosilylation catalysis to the alkylsilanes. Experimental and computational considerations of the mechanism are consistent with the sequential activation and 1,2-addition of hydrosilane across the unsaturated C-C bonds.

Polyisobutylene-Based Helical Block Copolymers with pH-Responsive Cationic Side-Chain Amino Acid Moieties by Tandem Living Polymerizations

Syntheses of diblock copolymers of isobutylene (IB) with amino acid-based monomers were carried out by a combination of living carbocationic and reversible addition–fragmentation chain transfer (RAFT) polymerizations. Cationic polymerization of IB followed by hydroboration oxidation produced hydroxyl end-capped polyisobutylene, which was subsequently converted into macro-chain-transfer agent (macro-CTA) for the RAFT polymerization of tert-butyloxycarbonyl (Boc)-protected amino acid-based monomers such as Boc-l-alanine methacryloyloxyethyl ester (Boc-l-Ala-HEMA) and Boc-l-leucine methacryloyloxyethyl ester (Boc-l-Leu-HEMA). The block length and molecular weight could be controlled while maintaining a narrow molecular weight distribution. These block copolymers form core–shell type micellar structure in methanol—a good solvent for side-chain amino acid block but bad solvent for polyisobutylene segment. Specific rotation and circular dichroism (CD) studies indicated the chiral nature of the block copolymers ...

Cationic polymerization of isobutylene by FeCl3/ether complexes in hexanes: An investigation of the steric and electronic effects of ethers

The polymerization of isobutylene (IB) in hexanes at 0 °C initiated by tert-butylchloride (t-BuCl) and coinitiated by GaCl3 or FeCl3•diisopropyl ether (i-Pr2O) complexes to produce polyisobutylene with high exo olefin content (HR PIB) has been previously reported [1]. In an effort to further improve the efficiency of the catalytic system, we have performed systematic studies on the effect of the nature of the ether used in the FeCl3•ether complex on the polymerization. Investigation of the properties of the FeCl3•ether complexes possessing unique steric and electronic properties via attenuated total reflectance (ATR) FT-IR, and solubility studies have revealed several interesting characteristics that may be useful in further optimizing the present initiating system. For example, long alkyl chains reduce the solubility of the catalyst resulting in decreased polymerization rates. On the other hand, the polymerization rate can be increased by incorporating electron-withdrawing groups on the ether, which affects both the complexation equilibrium and the basicity of the ether. These investigations have identified key characteristics that should be present in the ether in order to increase reactivity while maintaining high levels of exo-olefin in HR PIB.