Helix Induction to Polyfluorenes Using Circularly Polarized Light: Chirality Amplification, Phase-Selective Induction, and Anisotropic Emission

Chirality induction (preferred-handed helix induction) to poly(9,9-dioctylfluorene-2,7-diyl) (poly(DOF)), poly(9,9-didodecylfluorene-2,7-diyl) (poly(DDF)), and poly(9,9-dihexylfluorene-2,7-diyl) (poly(DHF)) using circularly polarized light (CPL) was thoroughly investigated mainly using film samples. We found that the presence of the β-phase is indispensable in chirality induction to poly(DOF) which suggests the importance of interchain interactions and that chirality induction first occurs preferentially in the β-phase and then extended to the α-phase. Chirality induction only to the β-phase was attained by irradiating at the β-phase absorbance band (435 nm) or by irradiating the full wavelength range for a short time while pure α-phase chirality is induced for poly(DHF) having no β-phase using an achiral aid molecule. Chirality induction is feasible for polymers having octyl and dodecyl chains, poly(DOF) and poly(DDF), whereas it is not possible for the polymer having a hexyl chain, poly(DHF), unless an ...