Aggregation Behaviors of Ladder-Type Poly(p-phenylene) in Dilute Solutions and Spin-Coated Films

Abstract

The polymer aggregation morphology in thin films strongly depends on the state of the solution and the film processing conditions, which lead to important impacts on the optoelectronic properties. In this work, the aggregation behaviors of ladder-type poly(p-phenylene) (Me-LPF) in dilute toluene solutions and spin-coated films are investigated by concentration- and temperature-dependent fluorescence spectroscopy and atomic force microscopy (AFM) combined with X-ray diffraction. Spin coating is normally a typical method for amorphous and isotropic films. In Me-LPF, the preassembly in solution plays an important role in aggregation behaviors in spin-coated film. The driving force of aggregation would be weak side-chain entanglement in the absence of intermolecular π–π interactions, which are very sensitive to temperature. The polymer chain aggregation is observed in dilute toluene solutions (>8 μg/mL) and spin-coated films at room temperature, which induces fluorescence quenching of the 0–0 emission band. It comes from enhanced energy transfer efficiency in aggregates by shortened intermolecular distance and ordered molecular orientation. These results supply a facile spin-coating process to prepare high order films, which show potential application in optoelectronic devices.