Phase Separation in Poly(9,9-dioctylfluorene)/Poly(methyl methacrylate) Blends

Abstract

Binary blends of the conjugated polymer poly(9,9-dioctylfluorene) (PFO) and the insulating polymer poly(methyl methacrylate) (PMMA) phase-separated and exhibited optical and electrical activity in light-emitting-diodes. The phase-separated PFO columns were uniformly packed and situated directly on a transparent hole-injecting contact. The length scales of lateral topographical features can be adjusted discretionarily by controlling the blend concentration and compositional ratio. The mechanism leading to the formation of lateral structures was investigated by comparing with the vertical segregation in polar conjugated polymer poly(9,9-bis(6-diethoxylphosphorylhexyl)fluorene) (PF-EP) blends with PMMA, which suggested that kinetics rather than interfacial free energy acted. In such lateral phase-separated structures, the phase-separated PFO domains were the optically and electrically active phase. This highlighted the potential opportunity as nanoscale light source for organic optoelectronic device applications with well-controllable properties.