Preparation and characterization of polyfluorene-based supramolecular π-conjugated polymer gels

Supramolecular π-conjugated polymer-based gels (SCPGs) are one important kind of semiconducting soft materials. Herein we demonstrate a poly(9,9-dioctylfluorene) (PFO) based on SCPG in 1,2-dichloroethane (DCE). The PFO/DCE gel exhibits a characteristic photoluminescence profile distinguished from other polymorphisms. The emission peak at ca. 550 nm evidences the aggregate or excimer mechanism of the low-energy emission band in polyfluorenes. Thermoreversible sol-gel transition of PFO/DCE gel has been investigated by temperature-resolved fluorescence spectroscopy and differential scanning calorimetry (DSC). The formation mechanism of PFO/DCE gel has been proposed according to the scanning tunneling microscopy (STM) and small-angle X-ray scattering (SAXS) analysis. The obtained xerogel via freeze-drying exhibited regularly interpenetrated pores with the size of about 2-5 μm. Gelation of π-conjugated polymers paves a promising way to prepare porous soft semiconductors with potential applications of sensors and actuators.