The Orientation and Photophysical Properties of Polyfluorene-based Conjugated Polymers in Ultrahigh Molecular Weight Polyethylene Films

The highly oriented light-emitting films of polyfluorene-based conjugated polymers blended with ultrahigh molecular weight polyethylene (U-PE) are prepared by using a tensile deformation technique. The high dichroic ratios of blue light (58 in photoluminescence (PL)) from the poly (9,9-dioctylfluorene) (PFO)/U-PE blending film and of green light (36 in PL) from the poly(9,9-dioctylfluorene) containing one fluorenone unit (PFF)/PFO/U-PE blending film are obtained. In the PFO/U-PE blending film, the variation of the photophysical properties of the blending films with the drawing ratio is discussed in detail which suggests that the conjugated polymer chains are forced to a highly dispersed and oriented condition in the oriented PE matrix. The green band (g-band) of the blending film containing PFF is also studied and found in such a highly oriented condition, and a set of new evidence was obtained demonstrating the keto-defect origin of g-band.