Optical properties of conductive polymers in their solutions and electrospun fibers

Abstract

The studies on optical properties of various conductive polymers (i.e., poly(2-methoxy-5-(2 ’-ethylhexyloxy)-1,4-phenylene vinylene) (MEH-PPV), poly(ethylhexyloxy-octyloxy-p-phenylene ethynylene) (EHO-OPPE), poly(2,7-(9,9-bis(2-ethylhexyl)fluorene)) (BEH-PF)) either in their solution or electrospun fibrous form were successfully reported here. First, a versatile method for tuning optical properties of MEH-PPV in its solution with 1,2-dichloroethane was accomplished by reacting with pyridinium formate (PF), a volatile organic salt. Adjusting the concentration of PF in the solution led to a systematic control for the position of the absorption and the photoluminescent (PL) spectra of MEH-PPV. The changes in the emission color from orange to yellow and, finally, to green were observed by naked eyes in the MEH-PPV solution that contained 0.1 and 10 vol.-% of PF, respectively. The changes in the optical properties were due to chemical modifications along the main chain and the side groups of MEH-PPV. For the studies on the electrospinning of EHO-OPPE and BEH-PF, ultrafine fibers from their blend solutions with an electrospinnable and inert template polymer, i.e., polystyrene (PS) were successfully prepared. Scanning electron microscopy (SEM) and Fourier-transformed infrared (FT-IR) spectroscopy were respectively used to observe the morphology and chemical integrity of the electrospun fibers. The optical properties (i.e., absorption and PL emission) were investigated by UV-Visible and PL spectroscopy, respectively. Moreover, the corresponding spin-coated and solution-cast films were also studied for comparison.