Репозиторий Университета

© 2019 Elsevier Ltd The effect of different initiators (tert-butyl chloride (t-BuCl) and 2-chloro-2-phenylpropane (CumCl) on the cationic polymerization of isobutylene co-initiated by acidic chloroferrate imidazole-based ionic liquid emimCl-FeCl3 (emimCl: 1-ethyl-3-methylimidazolium chloride, molar fraction of FeCl3 (χ(FeCl3)) ≥ 0.6) in the presence of diisopropyl ether at 0 °C and [IB] = 5.2 M has been investigated. Generally, the use of all above-mentioned initiators results in increase of the monomer conversion from 30% to 60% as well as in decrease of molecular weight from 2500 g mol−1 to 1100 g mol−1 and polydispersity from 2.6 to 1.7, respectively, but does not influence the content of exo-olefin end group. It was demonstrated that CumCl does not initiated directly the polymerization at 0 °C or −20 °C, rather, it decomposed with the formation of the proton, a true initiator of the polymerization. It was also found that addition of small amounts (1% by volume) of benzene or its derivatives into the polymerization system leads to further increase of the monomer conversion (>90%). The rate of isobutylene polymerization depends on basicity of aromatic compounds added and increases in the following order: benzene < toluene ≈ mesitylene.

© 2018 Elsevier Ltd 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.