Cationic polymerization of hydrocarbon monomers induced by complexes of acyl halides with Lewis acids 6. The effect of 2,6-dimethylpyridine on the polymerization of isobutylene

The effect of 2,6-dimethylpyridine on the cationic polymerization of isobutylene inn-hexane and dichloromethane at -78 °C under the action of complexes of acetyl bromide with AlBr₃ of the compositions 1 : 1 and 1 : 2 was investigated. 2,6-Dimethylpyridine significantly depresses the initiation and chain transfer processes involving free protons and also retards the proton elimination from growing carbocations.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1180–1183, May, 1996.     

1H NMR spectroscopic study of theert-butyl chloride—aluminum bromide cationic initiating system

The interaction oftert-butyl chloride with aluminum bromide in methylene dibromide at −30°C leads to the formation of two types of adducts, which give signals with δ 2.4 and 3.2 in the¹H NMR spectra in addition to that of free alkyl halide. these signals are attributed to a polarized complex (PC) and ion pair (IP), respectively. An excess of AlBr₃ shifts the equilibria toward IP. The latter contains more AlBr₃ than the polarized complex. Based on the spectral data, we calculated the limiting values of some equilibrium constants. The ability of AlBr₃ to solvate counterions is consistent with the results of isobutylene polymerization under the action of the initiating Bu^tCl−AlBr₃ system at different ratios of the starting concentrations [AlBr₃]₀/[Bu^tCl]₀. An increase in this ratio results in both the acceleration of polymerization and an increase in the relative role of chain transfer reactions. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2217–2222, November, 1998.     

Direct functionalization of polyisobutylene by living initiation with α‐methylstyrene epoxide

This article describes the synthesis and characterization of polyisobutylene (PIB) carrying one primary hydroxyl head group and a tertiary chloride end group, [Ph? C(CH₃)(CH₂OH)–PIB–CH₂? C(CH₃)₂Cl] prepared with direct functionalization via initiation. The polymerization of isobutylene was initiated with the α‐methylstyrene epoxide/titanium tetrachloride system. Living conditions were obtained from ?75 to ?50 °C (198–223 K). Low molecular weight samples (number‐average molecular weight ～ 4000 g/mol) were prepared under suitable conditions and characterized by Fourier transform infrared and ¹H NMR spectroscopy. The presence of primary hydroxyl head groups in PIB was verified by both methods. Quantitative Fourier transform infrared with 2‐phenyl‐1‐propanol calibration and ¹H NMR performed on both the hydroxyl‐functionalized PIB and its reaction product with trimethylchlorosilane showed that each polymer chain carried one primary hydroxyl head group. The synthetic methodology presented here is an effective and simple route for the direct functionalization of PIB. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1005–1015, 2002     

Effect of Spectrum of Acidity of Zeolites of Various Structural Types on Their Catalytic Characteristics in the Synthesis of Ethyl tert-Butyl Ether

The catalytic properties of zeolites of various structural types in the liquid phase synthesis of ethyl tert-butyl ether from isobutylene and ethanol have been studied. The activity and selectivity of the catalysts depend on the concentration and strength of the acid centers. A possible mechanism for the synthesis of ethyl tert-butyl ether is proposed, suggesting that isobutylene and ethanol are activated on the weak and strong acid centers respectively.     

Amphiphilic conetworks. III. Poly(2,3‐dihydroxypropyl methacrylate)–polyisobutylene and poly(ethylene glycol) methacrylate–polyisobutylene based hydrogels prepared by two‐step polymer procedure

This article describes the synthesis and characterization of new amphiphilic polymer conetworks containing hydrophilic poly(2,3‐dihydroxypropyl methacrylate) or poly(ethylene glycol) methacrylate (PEGMA) and hydrophobic polyisobutylene chains. This conetworks were prepared by a two‐step polymer synthesis. In the first step, a cationic copolymer of isobutylene and 3‐isopropenyl‐α,α‐dimethylbenzyl isocyanate (IDI) was prepared. The isocyanate groups of the IB‐IDI random copolymer were subsequently transformed in situ to methacrylate (MA) groups in reaction with 2‐hydroxyethyl methacrylate (HEMA). In the second step, the resulting MA‐multifunctional PIB‐based crosslinker, PIB(MA)_n, with an average functionality of approximately four per chain, was copolymerized with 2,3‐dihydroxypropyl methacrylate or poly(ethylene glycol) methacrylate by radical mechanism in tetrahydrofuran giving rise to amphiphilic conetworks containing 11–60 mol % of DHPMA or 10–12 mol % of PEGMA. The synthesized conetworks were characterized with solid‐state ¹³C‐NMR spectroscopy and differential scanning calorimetry. The amphiphilic nature of the conetworks was proved by swelling in both water and n‐heptane. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4074–4081, 2007     

Ziegler catalytic systems in cationic polymerization

The ternary catalytic system AlBuⁱ ₃-TiCl₄-CCl₄ initiates the cationic polymerization of isobutylene in toluene at room temperature, whereas the binary combinations of these components do not induce isobutylene polymerization. At low CCl₄ concentrations, the polymerization rates decrease sharply with time, and the quantitative yield of the polymer is achieved at an excess of CCl₄ with respect to the titanium and aluminum components. The molecular weights of the polymers range within 1300–4000, and the index of polydispersity, as a rule, does not exceed 2.7. The influence of the conditions of component mixing (order of addition, duration of exposure prior to addition of the third component) on the yield and molecular weight of the polymerization product was found. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 711–714, April, 1999.     

One‐pot synthesis of isocyanate and methacrylate multifunctionalized polyisobutylene and polyisobutylene‐based amphiphilic networks

Amphiphilic polymer networks consisting of hydrophilic poly(2‐hydroxyethyl methacrylate) (PHEMA) and hydrophobic polyisobutylene (PIB) chains were synthesized from a cationic copolymer of isobutylene (IB) and 3‐isopropenyl‐α,α‐dimethylbenzyl isocyanate (IDI) prepared at ?50 °C in dichloromethane in conjunction with SnCl₄. The isocyanate groups of this random copolymer, PIB(NCO)_n, were subsequently transformed in situ to methacrylate (MA) groups in the dibutyltin dilaurate‐catalyzed reaction with 2‐hydroxyethyl methacrylate (HEMA) at 30 °C. The resulting PIB(MA)_n with number–average molecular weight 8200 and average functionality F_n ～ 4 per chain was in situ copolymerized radically with HEMA at 70 °C, giving rise to the amphiphilic networks containing 41 and 67 mol % HEMA. PHEMA–PIB network containing 43 mol % HEMA was also prepared by radical copolymerization of PIB(MA)_n precursor with HEMA using sequential synthesis. An amphiphilic nature of the resulting networks was proved by swelling in both water and n‐heptane. PIB(NCO)_n and PIB(MA)_n were characterized by FTIR spectroscopy, SEC and the latter also by ¹H NMR spectroscopy. Solid state ¹³C NMR spectroscopy was used for characterization of the resulting PHEMA–PIB networks. Whereas single glass‐transition temperature, T_g = ?67.4 °C, was observed for the rubbery crosslinked PIB prepared by reaction of PIB(NCO)_n with water, the PHEMA–PIB networks containing 67 and 41 mol % HEMA showed two T_g's: ?70.4 and 102.7 °C, and ?63 and 107.2 °C, respectively. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2891–2900, 2006     

Electrolyte Regulation towards Stable Lithium‐Metal Anodes in Lithium–Sulfur Batteries with Sulfurized Polyacrylonitrile Cathodes

Lithium–sulfur (Li–S) batteries are highly regarded as the next‐generation energy‐storage devices because of their ultrahigh theoretical energy density of 2600 Wh kg^?1. Sulfurized polyacrylonitrile (SPAN) is considered a promising sulfur cathode to substitute carbon/sulfur (C/S) composites to afford higher Coulombic efficiency, improved cycling stability, and potential high‐energy‐density Li–SPAN batteries. However, the instability of the Li‐metal anode threatens the performances of Li–SPAN batteries bringing limited lifespan and safety hazards. Li‐metal can react with most kinds of electrolyte to generate a protective solid electrolyte interphase (SEI), electrolyte regulation is a widely accepted strategy to protect Li‐metal anodes in rechargeable batteries. Herein, the basic principles and current challenges of Li–SPAN batteries are addressed. Recent advances on electrolyte regulation towards stable Li‐metal anodes in Li–SPAN batteries are summarized to suggest design strategies of solvents, lithium salts, additives, and gel electrolyte. Finally, prospects for future electrolyte design and Li anode protection in Li–SPAN batteries are discussed.     

Living Cationic Sequential Block Copolymerization of Isobutylene with 4‐tert‐Butoxystyrene: Synthesis and Characterization of Poly(p‐hydroxystyrene‐b‐isobutylene‐b‐p‐hydroxystyrene) Triblock Copolymers

The living polymerization of p‐tert‐butoxystyrene (tBuOS) was studied in methylcyclohexane (MeChx)/methylchloride (MeCl) 60/40 v/v solvent mixture at –80°C. The model initiator 1,1,‐ditolylethylene (DTE) capped 2‐chloro‐2,4,4‐trimethylpentane (TMPCl) was formed in situ in conjunction with TiCl₄. Lowering the Lewis acidity by the addition of Ti(OIp)₄ was necessary to induce a rapid and controlled polymerization of tBuOS. Well‐defined polymers with controlled molecular weights, however, were only obtained at a narrow [Ti(OIp)₄]/[TiCl₄]=0.83–0.86 ratio. Above this ratio, the polymerization of tBuOS was slow and became absent at [Ti(OIp)₄]/[TiCl₄]≥1.18. At ratios lower than 0.83, the polymerization was too rapid and the initiator efficiency was lower than 100%. The living polymerization of tBuOS was also studied with SnBr₄ as Lewis acid. After capping TMPCl with DTE, Ti(OIp)₄ was added to reach [Ti(OIp)₄]/[TiCl₄]=1.2, followed by the addition of tBuOS and SnBr₄. SnBr₄ induced a well‐controlled living polymerization approximately first order in [SnBr₄], and the polymers exhibited close to theoretical M _ns and low polydispersity indices (PDI<1.2). The success of the method was also demonstrated by the clean synthesis of poly(isobutylene‐b‐p‐tert‐butoxystyrene) PIB‐b‐PtBuOS diblock copolymers. PtBuOS‐b‐PIB‐b‐PtBuOS triblock copolymer thermoplastic elastomers were prepared by employing 5‐tert‐butyl‐1,3‐bis(1‐methoxy‐1‐methylethyl)benzene (DCE) as a difunctional initiator for the living polymerization of IB followed by capping with DTE and substitution of TiCl₄ with SnBr₄ for the polymerization of tBuOS. Deprotection of the triblock copolymer in the presence of catalytic amount of HCl yielded poly(p‐hydroxystyrene‐b‐isobutylene‐b‐p‐hydroxystyrene) (PHOS‐b‐PIB‐b‐PHOS). PHOS‐b‐PIB‐b‐PHOS with 39.3 wt% p‐hydroxystyrene content exhibited typical characteristic of a thermoplastic elastomers (TPEs) with tensile strength of 18 MPa and ultimate elongation of 300%.     

Pressure and volume dependence of thermal conductivity and isothermal bulk modulus up to 1 GPa for poly(isobutylene)

The thermal conductivity λ and heat capacity per unit volume ρc_p of poly(isobutylene)s, one 2.8 in weight average molecular weight and one 85 kg mol⁻¹ in viscosity average molecular weight (PIB-2800 and PIB-85000), have been measured in the temperature range 170–450 K at pressures up to 2 GPa using the transient hot-wire method. At 297 K and atmospheric pressure, λ = 0.115 W m⁻¹ K⁻¹ for PIB-2800 and λ = 0.120 W m⁻¹ K⁻¹ for PIB-85000. The bulk modulus B_T has been measured in the temperature range 170–297 K up to 1 GPa. At atmospheric pressure, the room temperature bulk moduli B_T are 2.0 GPa for PIB-2800 and 2.5 GPa for PIB-85000 with dB_T/dp = 10 for both. These data were used to calculate the volume dependence of λ, At room temperature and atmospheric pressure (liquid phase) we find g = 3.4 for PIB-2800 and g = 3.9 for PIB-85000, but g depends strongly on temperature for both molecular weights. The difference in g between the glassy state and liquid phase is small and just outside the inaccuracy of g of about 8%. The best predictions for g are given by the theoretical model of Horrocks and McLaughlin. We have found that PIB exhibits two relaxations, where one is associated with the glass transition. The value for dT_g/dp at atmospheric pressure (for the main glass transition) is about 0.21 K MPa⁻¹ for both molecular weights. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1781–1792, 1998