Morphology Control in Poly(9,9-di-n-octyl-2,7-fluorene) Spherulite Particles Prepared via Dispersion Polymerization

Crystallinity in polymers is an important means for tuning the bulk properties of the material. Poly(di-n-octylfluorene) (PFO) is a semiconducting polymer with a multitude of semicrystalline morphologies, which can be induced by physical treatment. Here we present a synthetic method where narrowly dispersed PFO particles are produced while the morphological composition of the semicrystalline colloids can be controlled. The desired degree of crystallinity can be adjusted by varying the concentration of a surface active polymer stabilizing the polymer particles during dispersion synthesis. While low concentrations of the stabilizer polymer lead to mixed morphology spherulite particles, higher concentrations lead to a controlled condensation-crystallization mechanism resulting in spherical particles with crystalline content. The birefringence characteristics as well as the fluorescence behavior of the resulting particles can be precisely tuned depending on the respective morphological phase and the degree of crystallinity.