Cationic Macromolecular Design and Synthesis Using Furan Derivatives

Abstract

General methodologies for the synthesis of block copolymers and functional polymers using furan derivatives are reported on the basis of a study of addition reactions of 2-substituted furans to living polyisobutylene (PIB+). Rapid and quantitative monoaddition of 2-methylfuran (2-MeFu) and 2-tert-butylfuran (2-tBuFu) to PIB+ has been observed in conjunction with TiCl4 as Lewis acid in hexanes (Hex)/CH2Cl2 or CH3Cl 60/40 v/v at −80 °C and with BCl3 in CH3Cl at −40 °C, in the presence of proton trap. Upon monoaddition, the formation of the stable allylic cation was confirmed by trapping the resulting cation with tributyltin hydride, which yielded PIB with dihydrofuran functionality. Quenching with methanol resulted in the quantitative formation of 2-alkyl-5-PIB-furan. The stable allylic cation was found to be an efficient initiating species for the polymerization of methyl vinyl ether (MeVE), yielding P(IB-b-MeVE) block copolymers by sequential monomer addition with up to 75% crossover efficiency. 2-PIB-Fu, a polymeric capping agent, was obtained in quantitative yields in a reaction of PIB+ with 2-Bu3SnFu in Hex/CH3Cl 60/40 v/v in the presence of TiCl4 at −80 °C. In a subsequent reaction of 2-PIB-Fu with living PIB+, under conditions similar to capping PIB+ with 2-tBuFu, close to quantitative coupling of the two PIB chains was achieved. The concept of coupling a living cationic polymer with an ω-furan functional polymer to obtain AB-type linear block copolymers and for the synthesis of ABC- and AA‘B-type three-arm star-block copolymers is presented.