Cationic macromolecular engineering via furan derivatives

Abstract

General methodologies for the synthesis of linear and star-block copolymers and functional polymers using furan derivatives are reviewed, based on a study of addition reactions of 2-substituted furans to living polyisobutylene (PIB+). Rapid and quantitative mono-addition of 2-alkyl (and aryl)furans (2-R-Fu), a new class of non-(homo)polymerizable monomers, to PIB+ has been observed in conjunction with TiCl4 as Lewis acid in hexane/CH2Cl2 or CH3Cl 60/40 (v/v) at −80 °C and with BCl3 in CH3Cl at −40 °C, in the presence of proton trap. The resulting stable allylic cation (PIB-Fu+-R) was found to be an efficient initiating species for the polymerization of methyl vinyl ether (MeVE). Using 2,5-bis[1-furanyl)-1-methylethyl]-furan, coupling of living PIB was found to be rapid and quantitative in hexanes(Hex)/CH3Cl 60/40 or 40/60 (v/v) solvent mixtures at −80 °C in conjunction with TiCl4, as well as in CH3Cl at −40 °C with BCl3 as Lewis acid. The kinetics of addition of 2-R-Fu to PIB+ was investigated by UV-vis spectroscopy. Based on these results and those obtained with substituted 1,1-diarylethylenes earlier, the absolute rate constants of ionization (ki), reversible termination (k−i) and propagation (kp) in the polymerization of IB have been determined. By a similar approach the corresponding rate constants have also been determined for the polymerization of styrene.