The nature of the double bond in low molecular weight polyisobutylenes and “polybutene” copolymers

Abstract

Olefin types were quantitatively determined by PMR and infrared spectroscopic analyses in polyisobutylenes and commercial polybutenes of Mn ranging from 500 to 2000. The catalyst and the polymerization conditions were found to have a great influence on the olefin type produced. In polyisobutylenes produced with BF3, the terminal vinylidene formed initially can diminish under the isomerizing influence of the catalyst. In polyisobutylenes synthesized with AlCl3, the major olefin type is °C(R)=CH(CH3). Its formation is explained by a multistep termination which involves tail‐to‐tail coupling. Internal vinyl‐idenes were also identified in most of the samples. Their formation can be explained by a skeletal rearrangement either in the termination step, or during polymer double‐bond isomerizations. In most polymers, the spectroscopically measured unsaturation was lower than that determined by hydrogenation. The difference is attributed to the presence of tetrasubstituted olefins.

Kinetic and Mechanistic Studies of the Polymerization of Isobutylene Catalyzed by EtAlCl2/Bis(2-chloroethyl) Ether Complex in Hexanes

“…9 Bochmann and co-workers developed a new zinc-based initiator system to produce HR PIB at room temperature. 10 Krossing and co-workers employed novel univalent gallium salts [Ga(C 6 H 5 F) 2 4 ] − (where R F = C(CF 3 ) 3 ) to achieve synthesis of HR-PIB in several solvents including CH 2 Cl 2 and toluene. 11 Voit and co-workers reported synthesis of HR PIB using M(II) complexes (M = Mn, Cu, Zn, Mo) as catalysts.…”

Greener, cleaner polymerization of isobutene

“…The spectrum is in accordance with that for PIB with prominent peaks at 1·42 and 1·11 ppm corresponding to the methylene and methyl groups of the repeat unit, respectively. Integration of peaks in the olefi nic region based on assignments previously described in the literature [61][62][63] showed the product contains essentially equivalent amounts of exoolefi nic and endo-olefi nic end groups (ca. 53% exo).…”

Synthesis, characterization and biological activity of C60 derivative

“…Additionally, there is a visible shoulder peak (e) at δ = 4.82 to the downfield exo ‐olefin peak (h 1 ) at δ = 4.84 even though MWD of PIB was narrow ( M w / M n = 1.22). This weak resonance at δ = 4.82 may be assigned either to C H 2  protons of internal vinylene resulting from carbenium ion rearrangements or to the two identical protons of C H 2  in the coupled PIBs formed by the addition of a growing PIB carbenium ion (I) to the exo ‐olefinic end group (A) in another PIB chain 29–32. The coupling reactions could not be avoided when β‐proton abstraction from the growing carbenium ions (I) was not sufficiently rapid.…”

“…On the basis of the integral calculation, the PIB chains obtained at −40 °C were only 6.2% of tert ‐Cl terminal groups, and the termination via chlorine transfer from counteranion did hardly take place during polymerization. Instead, the PIB obtained at −40 °C had another 61.9% of exo ‐ (δ f1,2 = 4.64, 4.85 ppm) terminal groups, 20.9% of endo ‐ (δ h = 5.15 ppm) terminal groups due to β‐proton elimination and 11.0% of isomer (δ = 4.82 ppm) C H 2  protons in internal vinylene mainly resulting from carbenium ion rearrangements or in the coupled PIBs formed by the addition of a growing PIB carbenium ion (I) to the exo ‐olefinic end group (A) in another PIB chain 29–32. The serious chain transfer to monomer did also simultaneously take place to form new polymer chains with 67.8% of tert ‐butyl head groups according to the characteristic resonance at δ = 0.99 ppm.…”