Morphological transformation and photophysical properties of rod-coil poly[2,7-(9,9- Dihexylfluorene)]-block-poly(acrylic acid) in solution

The synthesis, morphology, and photophysical properties of PF-b-PAA with different coil lengths in dilute solutions of dichloromethane/methanol are reported. A tape-like lamellar morphology is observed at a short coil length of PF-b-PAA. As the coil length increases, a large compound micelle, sphere, or vesicle is observed with different methanol contents because of the enhancement of the PAA swelling with methanol and the interfacial tension between the PF core and the PAA corona. Upon further increase of the coil length, an inverted morphology of a sphere or rod with a PF corona and PAA core is first observed but the core/corona is then reversed at a high methanol content as a result of the enhanced solubility of PAA. The morphological transformation leads to a significant variation in optical absorption or fluorescence characteristics because of the possible H-aggregate formation.