Anionic polymerization of phenyl-substituted isoprene derivatives : polymerization behaviour and cyclization-enabled fluorescence

Abstract

1,3-Dienes are important monomers for living anionic polymerization. However, phenyl-substituted diene monomer structures have been rarely investigated. Based on DFT calculations and 13C NMR spectroscopy, a discrepancy in the reactivity of the two monomers 1-phenyl isoprene (1PhI) and 4-phenyl isoprene (4PhI) in anionic polymerization is expected. Starting from a Wittig reaction including an optimized extraction procedure, disubstituted 1,3-dienes were obtained that resulted in polymers with different degrees of 1,3-incorporation. The polymers have been characterized by 1H NMR spectroscopy and using different SEC conditions. Molecular weights of up to 48.8 kg mol−1 with narrow dispersities (Đ ≤ 1.13) were achieved. The addition of the modifier THF led to an initial increase of vinyl units as well as a loss of control over the polymerization of 4PhI. Increasing the THF concentration further resulted in a rather unusual decrease of the vinyl units and ended with more than 80% 1,4-units in pure THF. Copolymeriza