Carbocationic Polymerization Of Isobutylene Research Articles

Polyisobutylene-b -Poly(N,N -diethylacrylamide) well-defined amphiphilic diblock copolymer: Synthesis and thermo-responsive phase behavior

Polyisobutylene-b-poly(N,N-diethylacrylamide) (PIB-b-PDEAAm) well-defined amphiphilic diblock copolymers were synthesized by sequential living carbocationic polymerization and reversible addition-fragmentation chain transfer (RAFT) polymerization. The hydrophobic polyisobutylene segment was first built by living carbocationic polymerization of isobutylene at −70 °C followed by multistep transformations to give a well-defined (Mw/Mn = 1.22) macromolecular chain transfer agent, PIB-CTA. The hydrophilic poly(N,N-diethylacrylamide) block was constructed by PIB-CTA mediated RAFT polymerization of N,N-diethylacrylamide at 60 °C to afford the desired well-defined PIB-b-PDEAAm diblock copolymers with narrow molecular weight distributions (Mw/Mn ≤1.26). Fluorescence spectroscopy, transmission electron microscope, and dynamic light scattering (DLS) were employed to investigate the self-assembly behavior of PIB-b-PDEAAm amphiphilic diblock copolymers in aqueous media. These diblock copolymers also exhibited thermo-responsive phase behavior, which was confirmed by UV-Vis and DLS measurements. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 1143–1150

Polymerization of Isobutylene by GaCl3 or FeCl3/Ether Complexes in Nonpolar Solvents

The carbocationic polymerization of isobutylene (IB), co-initiated by GaCl3 or FeCl3·dialkyl ether 1:1 complexes has been investigated in hexanes in the −20 to 10 °C temperature range. In contrast to AlCl3·diisopropyl ether (AlCl3·i-Pr2O) complexes,(1) GaCl3·i-Pr2O and FeCl3·i-Pr2O readily co-initiate polymerization with 2-chloro-2,4,4-trimethylpentane (TMPCl) or tert-butyl chloride (t-BuCl) in the presence or absence of proton trap. In the absence of proton trap, chain transfer to monomer readily proceeded, resulting in close to complete monomer conversion and up to 85% exo-olefinic end group content. Diisopropyl ether complexes gave the highest polymerization rates, while nonbranched alkyl ether complexes were completely inactive. A polymerization mechanism is proposed to involve ether-assisted proton elimination to yield PIB exo-olefin, and the abstracted proton can subsequently start a new polymer chain by protonation of IB. Alternatively PIB+ may be deactivated by ion collapse to yield PIBCl, which can be reactivated by the Lewis acid. The reasons for the difference in behavior between the Ga and Fe catalysts and the Al-based catalysts are described.

Polymerization of Isobutylene by AlCl3/Ether Complexes in Nonpolar Solvent

The carbocationic polymerization of isobutylene (IB), co-initiated by AlCl3/ether complexes, has been reexamined and extended to different dialkyl ethers. In the absence of a proton trap, 2,6-di-tert-butylpyridine (DTBP), the polymerization of IB by the cumyl alcohol (CumOH)/AlCl3·nBu2O initiator/co-initiator system in dichloromethane/hexanes (80/20 v/v) at −40 °C gave high conversion to polyisobutylene (PIB) comprising exo-olefins with high selectivity, similar to that reported before by Vasilenko et al.(1, 2) However, in the presence of DTBP, polymerization was absent, suggesting that CumOH is not an initiator in conjunction with AlCl3·Bu2O, and the true initiator is adventitious water. Similarly, in the presence of DTBP in hexanes at 0 °C, polymerizations were absent not only with CumOH but with CumCl, tert-butanol, and 2-chloro-2,4,4-trimethylpentane. The polymerization of IB could be initiated only with adventitious water in the absence of DTBP, but monomer conversions and exo-olefin content (60–70%)...

Precision synthesis and characterization of thymine-functionalized polyisobutylene

A new two-step synthesis of polyisobutylene (PIB) with precisely one thymine functionality per chain (PIB-T) is reported. The primary hydroxyl-functionalized PIB (PIB-OH) precursor was prepared by direct functionalization via living carbocationic polymerization of isobutylene initiated by the α-methylstyrene epoxide/TiCl4 system. Matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-ToF MS) of a low molecular weight PIB-OH precursor demonstrated the effectiveness of direct functionalization by this method. A PIB-acrylate precursor (PIB-Ac) was obtained from such a PIB-OH, and the PIB-T was subsequently prepared by Michael addition of thymine across the acrylate double bond. MALDI-ToF MS of the products verified that all polymer chains carried precisely one thymine group. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3501–3506, 2010

Poly(acrylate‐b‐styrene‐b‐isobutylene‐b‐styrene‐b‐acrylate) Block Copolymers via Carbocationic and Atom Transfer Radical Polymerizations

A series of polyacrylate‐polystyrene‐polyisobutylene‐polystyrene‐polyacrylate (X‐PS‐PIB‐PS‐X) pentablock terpolymers (X=poly(methyl acrylate) (PMA), poly(butyl acrylate) (PBA), or poly(methyl methacrylate) (PMMA)) was prepared from poly (styrene‐b‐isobutylene‐b‐styrene) (PS‐PIB‐PS) block copolymers (BCPs) using either a Cu(I)Cl/1,1,4,7,7‐pentamethyldiethylenetriamine (PMDETA) or Cu(I)Cl/tris[2‐(dimethylamino)ethyl]amine (Me6TREN) catalyst system. The PS‐PIB‐PS BCPs were prepared by quasiliving carbocationic polymerization of isobutylene using a difunctional initiator, followed by the sequential addition of styrene, and were used as macroinitiators for the atom transfer radical polymerization (ATRP) of methyl acrylate (MA), n‐butyl acrylate (BA), or methyl methacrylate (MMA). The ATRP of MA and BA proceeded in a controlled fashion using either a Cu(I)Cl/PMDETA or Cu(I)Cl/Me6TREN catalyst system, as evidenced by a linear increase in molecular weight with conversion and low PDIs. The polymerization of MMA was less controlled. 1H‐NMR spectroscopy was used to elucidate pentablock copolymer structure and composition. The thermal stabilities of the pentablock copolymers were slightly less than the PS‐PIB‐PS macroinitiators due to the presence of polyacrylate or polymethacrylate outer block segments. DSC analysis of the pentablock copolymers showed a plurality of glass transition temperatures, indicating a phase separated material.

Carbocationic Polymerization of Isobutylene Using Methylaluminum Bromide Coinitiators: Synthesis of Bromoallyl Functional Polyisobutylene

The carbocationic polymerization of isobutylene (IB) was studied in conjunction with AlBr3, MeAlBr2, Me1.5AlBr1.5, and Me2AlBr coinitiators in hexanes(Hex)/methyl chloride (MeCl) 60/40 (v/v) solvent mixtures at −80 °C in the presence of a proton trap, 2,6-di-tert-butylpyridine. The observed Mns were directly proportional to monomer-to-initiator ratio with 2-chloro-2,4,4-trimethylpentane (TMPCl) as initiator and MeAlBr2, Me1.5AlBr1.5, and Me2AlBr coinitiators; however, with AlBr3 the Mns are much lower than the theoretical values. Chain extension “incremental monomer addition” (IMA) experiments resulting in bimodal distributions demonstrate that termination is operational with Me2AlBr. With MeAlBr2 the chain-extended PIBs exhibited close to theoretical Mns, but the molecular weigh distribution was broad. Using Me1.5AlBr1.5, Mn of the polymers increased in direct proportion and the molecular weight distributions remained narrow. 1H and 13C NMR spectroscopy of the polyisobutylene (PIB) obtained with Me1.5AlBr1.5 suggested virtually quantitative bromo end functionality. With MeAlBr2 and Me2AlBr the bromo functionality was lower (0.8−0), decreasing with the increase of Lewis acid concentration and polymerization time. The capping reaction of living polyisobutylene cation (PIB+) with 1,3-butadiene (BD) in Hex/MeCl 60/40 (v/v) solvent mixtures at −80 °C was also studied in conjunction with methylaluminum bromide coinitiators. Quantitative crossover reaction from living PIB chain end to BD followed by instantaneous termination and selective formation of 1,4-addition product bromoallyl functional PIB (PIB-AllylBr) was obtained only with Me1.5AlBr1.5 coinitiator.

Investigation of the effect of epoxide structure on the initiation efficiency in isobutylene polymerizations initiated by epoxide/TiCl 4 systems

The effect of the chemical structure of styrene-based epoxides, namely, styrene epoxide (SE), α-methylstyrene epoxide (MSE), p-methylstyrene epoxide (pM-SE) and α-methyl- p-methylstyrene epoxide (pM-MSE), in conjunction with TiCl 4, on the initiation efficiency ( I eff) in the carbocationic polymerization of isobutylene (IB) was investigated. SE yielded living polymerization, but the initiation efficiency was low when compared to MSE ( I eff=8% and 35%, respectively). pM-SE led to non-living IB polymerization, while pM-MSE revealed linear M n-conversion plot and narrow MWD with a non-linear first order rate plot. Among the epoxides investigated, MSE was the best initiator to scale up the one-step synthesis of polyisobutylenes (PIBs) carrying one primary hydroxyl head group and one tertiary chloride end group. The hydroxyl functionality of these PIBs determined by 1H-NMR was F n =1.09±0.16 from 24 experiments.

Carbocationic polymerization of isobutylene with alkyl aluminum chloride / methyl acrylate as the initiating system

A solution of alkyl aluminum chloride mixed with methyl acrylate (MA) was prepared and used as the initiating system for the polymerization of isobutylene (IB) carried out in a mixed butane-butene fraction at -50°C. The polymers obtained at different mole ratios AlRmCl3-m to methyl acrylate ([A1]/[MA]) were characterized by gel permeation chromatography (GPC). The results show that the uncontrolled polymerization process occurring in the absence of MA can be effectively controlled in the presence of small amounts of MA and that it produces polyisobutylene of a narrow molecular weight distribution. The 1H-NMR spectrum of the low-molecular-weight polymer shows that MA acts mainly as an inert electron donor to mediate the polymerization and also partly as an initiator.

Carbocationic polymerizations in supercritical carbon dioxide

The first carbocationic polymerization of isobutylene (IB) in supercritical carbon dioxide (SC·CO2) has been accomplished. It was demonstrated that in CO2 at 32.5°C and ∼ 120 bar the 2-chloro-2,4,4-trimethyl-pentane (TMPCl)/SnCl4 and TMPCl/TiCl4 initiating systems lead to ∼30% IB conversion, and gave polyisobutylenes (PIB) with Mn∼2000 and Mw/Mn∼2.0. This is the highest temperature IB was ever polymerized to reasonably high molecular weight products. Polymerizations at 32.5 °C under similar but conventional (non-living) conditions in the absence of SC·CO2 would yield only very low molecular weight oligomers (∼tetramers). The structure of the PIBs obtained in SC·CO2 is virtually identical to those obtained at much lower temperatures in conventional liquid-phase systems indicating the presence of chain transfer to monomer in both systems. In contrast to TMPCl initiated polymerizations, the 1,3-bis-(2-hydroxy-2-propyl)-5-tert-butylbenzene (HPBB) initiator in conjunction with BCl3 and SnCl4 yields only oligomers (Mn∼500) in SC·CO2.

Supported BF3 catalyst on crystalline polyolefins; carbocationic polymerization of isobutylene

This paper describes a new supported Lewis acid catalyst which involves BF3 species chemically bonded to the crystalline polyolefins, such as polypropylene and poly(1-butene). The supported catalysts are active in the carbocationic polymerization of isobutylene and are recovered and reused for many reaction cycles without significantly losing their activity. Several advantages, such as chemical and physical stabilities of the substrate, convenient implantation to load high concentration of catalyst to the substrate and high catalyst reactivity, have been observed. In addition, polyisobutylene obtained in this process has high terminal unsaturation.

Carbocationic polymerization of isobutylene by using supported Lewis acid catalyst on polypropylene

This paper describes a new class of supported Lewis acid catalysts which are based on partially crystalline polypropylene. The Lewis acid, such as EtAlCl2, is chemically bonded to the side chain of polypropylene and serves as catalyst for the cationic polymerization of isobutylene. This type supported catalyst can be easily recovered and reused for many reaction cycles without significant loss of its reactivity. The unique features of the structure of polypropylene offers the catalyst with high surface area and good mobility which account for the high catalytic activity. In addition, polypropylene is chemically and physically stable during the processes.

Investigation of the mechanism of living cationic polymerization of isobutylene by B11 NMR spectroscopy

The living carbocationic polymerization of isobutylene initiated by tri-cumyl-ether (1)/BCl3 and tricumyl-acetate(2)/BCl3 was investigated by B11 NMR spectroscopy in the presence and absence of DMSO. With BCl3, 1 yields tri-cumyl-chloride and BCl2OMe due to fast exchange reaction, while 2 forms complexes. If the 1/BCl3 mixture contains DMSO, well defined complexes can be detected, i.e., DMSO.BCl3 and BCl2OMe.DMSO. In the system 2/BCl3/DMSO neutral complexes with broad NMR signals are formed. In the presence of isobutylene (real polymerization mixture) the same complexes can be detected.

Investigation of 1,3,5-tris(2-metoxypropane)benzene/BCl3 initiated living isobutylene polymerization by C13 and B11 NMR spectroscopy

The living carbocationic polymerization of isobutylene initiated by 1,3,5-tris(2-methoxypropane) benzene (TriCumOMe)/BCl3 system was investigated by C13 and B11 NMR spectroscopy. The reaction between the TriCumOMe and BCl3 at-30°C in CH2Cl2 after 15 mins reaction time resulted in 1,3,5-tris(2-chloropropane) benzene (TriCumCl) and methyl-dichloroboronite (BCl2OMe). The same system in the presence of isobutylene yielded three-arm star, chlorine terminated telechelic polyisobutylene and BCl2OMe. No counterions, i.e., BCl3OMe⊝, BCl 4 ⊝ , or neutral boron complexes, e.g., TriCumOMe, 3BCl3 could be detected. The simultaneous measurement of static permittivity (direct monitoring method) showed different reaction rate patterns in the case of AMI method, and when the TriCumOMe+BCl3 mixture was aged and the polymerization was started by isobutylene.