Synthesis Of Conductive Poly(3, 4-ethylenedioxythiophene) Composite And Patterning Based On Organic Substrate

PEDOT has been investigated for many technological applications, such as antistatic coatings, conducting films, electrolumeniscent devices, capacitor, electrochromic window, photovoltaic cells, organic light-emitting diodes and sensors, because of its high conductivity, good stability and high transparency in oxide state. Like many inherent conductive polymers, the conjugated bond structure in PEDOT leads to a rigid conformation, and can not be processed via solution or melt. Although the PEDOT/PSS complex can be dispersed into water, and can be processed into films by spin-coating,dip-coating and inkjet-printing, but the PEDOT/PSS also suffers from low conductivity, commercially available PEDOT/PSS (Baytron P, Bayer Corporation) has a conductivity of less than 1 S/cm, PLEDs or PVs using this low-conductivity PEDOT/PSS as the anode exhibit very poor performance. And due to the strong acid nature, the PEDOT/PSS layer on ITO electrode is likely to be a source etching and corrosion, leading to a serious degradation of the device. So we persued new polymerization method and complex system to resolve the processing performance of PEDOT. The main contents of this thesis were shown as follow:1. A novel chemical strategy for fabricating flexible, transparent and conductive composite film by in-situ deposition PEDOT with nanofibrillar morphology on commercial plastics substrates was developed. The key points of the strategy included:(1) The surface sulfate groups (-SO4-) which are pre-implanted onto substrates surface by a confined photocatalytic oxidation (CPO) technique were critical both to improve the adhesion of the PEDOT with substrate via the static interactions, and to induce EDOT polymerizing onto substrate surface; (2) The nanofibrillar network morphology, which is critical to balance conductivity and transparency, was deliberately controlled by reaction recipe and parameters. Based on this design, with BOPP as model substrate, PEDOT/BOPP composite films about 20 nm in thickness, as high as 90% transparency and conductivity of 300 S/cm were obtained. Moreover, XPS data demonstrated that the implanted -SO4- on substrate surface is the primary dopant of deposited PEDOT, and the peeling test by 3M Scotch(?) adhesive tape proved the adhesion of substrate and PEDOT is drastically boasted. Combined with a photomask, a PEDOT micropattern on the polymer substrate was also fabricated.2. PEDOT-MWCNT nanocomposites were in situ synthesized in water-acetic acid solution of 2-hydroxy-4-methoxybenzophenone-5- sulfonic acid (BP-4) and H2SO4 as well as the water solution of H2SO4. SEM demanstrated that a well nanocomposite of PEDOT-MWCNT can be fabricated in water-acetic acid solution of BP-4 and H2SO4. The mophology of PEDOT-MWCNT composite was changed with the molar ratio of EDOT and MWCNT. In water-acetic acid solution of BP-4, when n(EDOT) is larger than a half of n(MWCNT), a composite with nanofibril mophology was achieved, and these nonafibrils are deposited with orientation; while n(EDOT) is less than a quarter of n(MWCNT), the obtained composite is coated by PEDOT uniformly. The electron pattern proves that the composite with nanofibil mopholgy is amorphous, which is stacked by the supermolecular interaction between PEDOT and MWCNT; but the PEDOT-coating composite is obtained by growth of PEDOT on the surface of MWCNT, which is crystal. And the alteration of mophology is also related to the solvent and temperature of polymerizion. The kinetics of polymerization is controlling the mophology. MWCNT act as a template during the stacking of PEDOT nanofibril and the growth of PEDOT chain on MWCNT surface. FTIR, UV-Vis and XRD prove PEDOT is present in the composite. Besides of PEDOT, some solvent molecules, such as acetic acid and BP-4, are also existed, acting as dopant of PEDOT, which demanstrated by XPS. The conductivity of PEDOT-MWCNT is much larger than that of PEDOT, and the composite with nanofibril mophology is more electrically conductive. The dispersibility of MWCNT in water is improved in a ceitain extent, and this give a chance for the application of the PEDOT-MWCNT to electronic devices.3. An aqueous complex of PEDOT was synthesized with the copolymer of sodium styrene sulfonate (SSNa) and butyl acrylate(BA) as dopant. FTIR and UV-Vis spectra proved BA is included in the complex. The conductivity data demonstrated that copolymerization with BA is an effective approach to elevate conductivity, which is about 40 time larger than that of PEDOT/PSS as the complex with 40 wt% of BA. SEM images illustrated that the films derived from PEDOT/P(SSNa-BA) is very even, and the size of gel in the film is becoming larger with the increase of BA composition, which is one of the reason for the increace of conductivity. XPS revealed that the more BA is used in the copolymer with SSNa, the more PEDOT is existed in the complex, leading to more domain of PEDOT, which is another reason for the increase of conductivity. The PEDOT/P(SSNa-BA) can form a preferable film with roughness about 6.71nm by spin-coating.