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

Maksim Hulnik; Diana Trofimuk; Pavel A Nikishau; Hüseyin Cem Kiliclar; Baris Kiskan; Sergei V Kostjuk

doi:10.1021/acsmacrolett.3c00384

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

ACS Macro Lett. 2023 Aug 15;12(8):1125-1131. doi: 10.1021/acsmacrolett.3c00384. Epub 2023 Jul 27.

Authors

Maksim Hulnik¹, Diana Trofimuk^{1

2}, Pavel A Nikishau¹, Hüseyin Cem Kiliclar³, Baris Kiskan³, Sergei V Kostjuk^{1

2}

Affiliations

¹ Research Institute for Physical Chemical Problems of the Belarusian State University, 14 Leningradskaya st., 220006 Minsk, Belarus.
² Department of Chemistry, Belarusian State University, 14 Leningradskaya st., 220006 Minsk, Belarus.
³ Department of Chemistry, Faculty of Science and Letters, Istanbul Technical University, 34469 Maslak, Istanbul, Turkey.

PMID: 37497867
DOI: 10.1021/acsmacrolett.3c00384

Abstract

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 (M_n = 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 M_n = 5000 g mol^-1 and Đ ∼ 2.0 was successfully synthesized using the same photoinitiating system.