Morphology Analysis of Electrospun Nanofibers based on Polymer Blends and Their Applications on Field Effect Transistor and Gas Sensing
Date Issued
2012
Date
2012
Author(s)
Chou, Chih-Chieh
Abstract
Electrospinning technique is a promising method in preparing nanofibers owing to its notable features such as low cost in fabrication, accessible adjustment in morphology, and continuously high-throughput production. In general, electrospun (ES) nanofibers are with high aspect ratio, which is beneficial for sensory or transistor device applications. However, the morphology as well as the application of the polymer-blend-based electrospun nanofibers has not been fully explored yet. Therefore, in this thesis, the influence of the morphology of the polymer-blend-based electrospun nanofibers on the performance of the organic field transistors (OFETs) and the gas sensory devices was investigated and the details were demonstrated as follows.
In Chapter 2, side-chains crystallinity effect on Morphology and nanofiber Field-Effect Transistor Characteristics of Crystalline Poly(3-hexlthiophene) and Poly acrylates Blends. We reported the morphology and nanofiber field-effect transistor characteristics based on crystalline poly(3-hexylthiophene)(P3HT) and poly(stearyl acrylates)(PSA) blends in different fabricated processes. P3HT/PSA nanofiber-based field effect transistor was fabricated via coaxial electrospinning technique. The average field effect mobility of the P3HT/PSA blend nanofibers was enhanced to be 3.21 × 10-2 cm2 V-1 s-1 while the blending ratio was equal to 1:0.2, which was two orders of magnitude higher than that (1.92 × 10-4 cm2 V-1 s-1) of P3HT. In addition, enhancing hole mobility of 1.22 × 10-2, 1.17 × 10-2 and 1.6 × 10-3 cm2 V-1 s-1 were also observed when the P3HT/PSA blend ratios were 1:0.5, 1:0.7 and 1:1, respectively. From the DSC analysis, the endothermic heats of P3HT were 10.32, 15.24, 13.83, and 13.96 J/g with different P3HT/PSA blending ratio of 1:0, 1:0.2, 1:0.5 and 1:1, respectively, which suggests that P3HT forms a more compact structure in the prepared nanofibers after blending with PSA. It might be attributed to that the compatibility between the P3HT hexyl chains and PSA probably enhances the molecular stacking within the thiophene rings of P3HT. Besides, the field-effect transistor based on spin-coated film also exhibited the similar effect, but the improving crystallinity effect is worse than ES process. Since the ES strong stretching force and the geometrical confinement associated with the ES process could induce the orientation of polymer chains along the long axis of fiber. As evidenced by TEM and XRD, the morphology studies showed that P3HT/PSA formed a core-sheath structure, which prevents the penetration of moisture and oxygen and results in an enhancement in the air stability of the P3HT. It was also found that at low PSA content, both face-on conformation and edge-on packing of P3HT molecules were coexisted. However, P3HT became randomly orientated as the amount of PSA was raised.
In Chapter 3, the NO gas sensing application of ES nanofibers prepared from thermo-responsive poly (NIPAAm-b-NMA)/1,2-diaminoanthraquinone (DAQ) blend was explored. The electrospun (ES) nanofibers of PNIPAAm-b-PNMA were prepared using a single-capillary spinneret and successfully embedded with 1,2-diaminoantraquinone (DAQ) to fabricate gas sensory devices. The high surface/volume ratio of the ES nanofibers efficiently enhanced the responsive speed compared to the drop-cast film, which reduced the reaction time from 90 min to 40 min. Moreover, the polymer matrix comprised of thermal responsive moiety of PNIPAAm and chemical cross-linking moiety of PNMA. The effects of the copolymer compositions on the morphology and properties of the prepared ES fibers were explored. The prepared nanofibers with DAQ revealed outstanding wettability and dimension stability in the aqueous solution. The sensing ability of the prepared nanofibers on the NO gas showed on/off characteristic as the temperatures varied from room temperature to 45 0C due to the LCST characteristic of PNIPAAm at 32 0C.
Subjects
electrospinning
transistor
sensor
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
index.html
Size
23.49 KB
Format
HTML
Checksum
(MD5):0a0b6a991618e3ce95a198d246e4b155