Morphology and Photophysical Properties of Electrospun Nanofibers Prepared from Conjugated Polymer Blends
Date Issued
2008
Date
2008
Author(s)
Wang, Cheng-Ting
Abstract
Electrospinning (ES) has emerged as a new technique to produce various functional polymer nanofibers. Conjugated polymers have extensively studied for various electronic and optoelectronic devices due to the excellent electronic and optoelectronic properties. The photophysical properties of conjugated polymers could be tuned through the approaches of blending or different synthetic ways which result in the enhancement of device characteristics. However, most of the above studies are based on thin film devices. The morphology and properties of conjugated polymers based nanofibers have not been fully explored yet. Only few ES nanofibers based on conjugated polymers were reported because of the limitations on molecular weight or solvents. In this study, luminescence electrospun poly(9,9-dioctylfluorenyl -2,7-diyl) (PFO)/2,3-dibutoxy-1,4-poly(phenylene vinylene) (DB-PPV)/poly(methyl methacrylate) PMMA ternary blend nanofibers were successfully produced. Effects of PFO/DB-PPV ratio on the morphology and photophysical properties were studied, where the PMMA weight percentage was fixed at 90 wt%.n the first part of this thesis, luminescent electrospun PFO/DB-PPV/PMMA ternary blend non-woven nanofibers were successfully prepared from different blending ratios of PFO/DB-PPV/PMMA (0/10/90-10/0/90). The field-emission scanning electron microscope (FE-SEM) studies showed that obtained fibers had the diameters around 400-700 nm and pore size in the range of 10-50 nm. The porous surface structure is resulted from the rapid evaporation of the high volatile chloroform solvent during the ES process. Transmission electron microscopy (TEM) studies showed morphology and size of PFO/DB-PPV micro phase separation in fibers, it was discovered that DB-PPV aggregated as spheres (1-60 nm) in the fibers, while PFO formed fiber-like structures (20-40 nm). The emission colors of the PFO/DB-PPV/ PMMA blend ES fibers changed from green, aquamarine blue, to blue, as the PFO composition increased. Our results showed that various light-emitting color ES fibers were produced through optimum polymer composition and Förster energy transfer. In additions, the high-light-emitting emission fibers obtained from the PFO/DB-PPV/ PMMA blend ratio of 9.9/0.1/90 had an excellent fluorescence quantum yield of 80%. In the second part of this thesis, highly aligned luminescent electrospun nanofibers were successfully prepared through PFO/DB-PPV/PMMA blends by using a single-capillary spinneret and a collector with a rectangular hole-gap. Uniform and aligned PFO/DB-PPV/PMMA blend fibers with diameters ranging from 600-800 nm were observed by FE-SEM. In addition, non-porous and smooth surface is exhibited in such blend aligned ES fibers since high boiling point chlorobenzene solvent is used during the ES process. Besides, a PFO/DB-PPV (10/0) system had a much higher dichroic ratio of 2 than a PFO/DB-PPV (0/10) system, whose dichroic ratio was 1.5. According to the above study, we took the advantage that PFO had a higher polarized emission than DB-PPV to perform different emission colors in PFO/DB-PPV/PMMA (9/1/90) blend system by tuning the angle of polarizer. The present study demonstrates that various light-emitting and polarized steady-state luminescence ES PFO/DB-PPV/PMMA ternary blend nanofibers were successfully produced, which could have potential applications as new light sources, sensory materials for smart textiles, or optoelectronic devices.
Subjects
electrospinning
congugated
nanofiber
SDGs
Type
thesis
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