Suzuki-Miyaura catalyst-transfer polycondensation of triolborate-type fluorene monomer: toward rapid access to polyfluorene-containing block and graft copolymers from various macroinitiators

• Published in: Polymer chemistry Vol. 11; no. 42; pp. 6832 - 6839
• Main Authors: Kobayashi, Saburo, Fujiwara, Kaiyu, Jiang, Dai-Hua, Yamamoto, Takuya, Tajima, Kenji, Yamamoto, Yasunori, Isono, Takuya, Satoh, Toshifumi
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 14.11.2020
• Subjects: Block copolymers; Catalysts; Chemical synthesis; Chloroform; Copolymers; Graft copolymers; Moisture content; Monomers; NMR; Nuclear magnetic resonance; Polymer chemistry; Polymerization
• ISSN: 1759-9954; 1759-9962
• DOI: 10.1039/d0py01127d

In this study, we demonstrated that the Suzuki-Miyaura catalyst transfer polycondensation (SCTP) of the triolborate-type fluorene monomer, viz . potassium 2-(7-bromo-9,9-dihexyl-9 H -fluorene-2-yl)triolborate, can be an efficient and versatile approach to the precise synthesis of poly[2,7-(9,9-dihexylfluorene)]s (PFs) and PF-containing block and graft copolymers. SCTP of the triolborate-type monomer proceeded rapidly in a THF/H 2 O mixed solvent at −10 °C using an iodobenzene derivative/Pd 2 (dba) 3 ·CHCl 3 / t -Bu 3 P initiating system. Kinetic and post-polymerization experiments revealed that SCTP proceeded via the chain-growth and living polymerization mechanisms. The most important feature of the present polymerization system is that only a small amount of base and water can sufficiently promote the reaction. The well-controlled nature of this polymerization system enabled the synthesis of high-molecular-weight PFs ( M n = 5-69 kg mol −1 ) with narrow dispersity ( M = 1.14-1.38) and α-end-functionalized PFs. Most importantly, PF-containing block and graft copolymers were successfully synthesized, beginning with various iodobenzene-functionalized macroinitiators; this was difficult to achieve by the conventional SCTP of pinacolboronate-type fluorene monomer. One of the key factors for the successful block and graft copolymer syntheses is the reduced water content in the polymerization medium, which suppressed the potential precipitation/aggregation of the macroinitiators. We demonstrated that the Suzuki-Miyaura catalyst transfer polycondensation of a triolborate-type fluorene monomer can be an efficient and versatile approach to the synthesis of polyfluorenes (PFs) and PF-containing block and graft copolymers.