Helical screw sense bias in chiral polyfluorene stimulated by solvent

Conjugated homopolymer poly(9,9-bis(3-(( S )-2-methylbutylpropanoate))fluorene) (PSF) with chiral pendants was synthesized and characterized. Dissolution experiments show that PSF is well dissolved in racemic limonene at high temperature and begins aggregating upon sequential cooling treatment. The corresponding assemblies were transferred to quartz plate by the spin-coating method. Comparably, film casting from chloroform solution was also prepared. Upon annealing thermal treatments, these PSF films exhibited perfect mirror circular dichroism (CD) Cotton effects and dissymmetry ratios. Optical absorption spectroscopy (UV-vis), CD, and fluorescence spectroscopy results reveal that chiral side chains successfully induced M - and P -helical structures in aggregates and films, and this significant difference was ascribed to their differential supramolecular conformations.