Synthesis of Highly Fluorescent and Soluble 1,2,4-Linking Hyperbranched Poly(arylenevinylene) Featuring Intramolecular Energy Funneling

The synthesis and optical properties of a highly soluble (>200 mg mL(-1)) and highly fluorescent (Phi(F) in film = 0.64) 1,2,4-linking hyperbranched poly(arylenevinylene) (1,2,4-hb-PAV) prepared via Wittig reaction of A(3) (biphenyl-tricarbaldehyde) and B-2 (phosphonium salt) monomers is reported. The molecular weight of 1,2,4-hb-PAV can be precisely controlled by the amount of the base (NaOCH3) used in the polymerization. The absorption and photoluminescence (PL) spectra of 1,2,4-hb-PAV shows distinct red-shifts compared to conventional 1,3,5-linking hyperbranched poly(arylenevinylene) (1,3,5-hb-PAV), attributed to the extended pi-conjugation along ortho- (1,2-) and para- (1,4-) links. The inherent energy gradient from the shorter branches to the longer conjugated stem in 1,2,4-hb-PAV enabled a characteristic energy funneling effect, which is absent in conventional hyperbranched polymer of 1,3,5-hb-PAV.