Synthesis and Characterization of High Dielectric Constant Polyaniline/Polyurethane Blends.

• Main Authors: Ching-Piou Chwang, 莊進標
• Other Authors: Sung-Nug Lee
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/74598985122763031687

博士 === 輔仁大學 === 化學系 === 92 === ABSTRACT As the device density of ULSI (Ultra-large-scale integrated circuit) is increasing, it is necessary to diminish the size of the device. With the purpose to keep the capacitance of a memory device as a constant, the best way to achieve the objective of miniaturization is to use dielectric material with high dielectric constant. Therefore, the purpose of this study is aimed to develop a new process so that a new type of material with high dielectric constant can be made. This project is started with the synthesis of anionic water-soluble PU resin, and the key question is how to choose the anionic monomer. The reaction of toluene diisocyanate (TDI) with dimethylol propionic acid (DMPA) or (1''-amino ethyl)-1-amino propane sulfonic acid sodium salt (ES-200) and other additives to form the structure of anionic polyurethane (PU)ionomer molecule has been proven by FT-IR spectroscopy. In aqueous solution, the surface tension of anionic PU ionomer molecule is seen to slightly increase with increasing concentration of ES-200. This is because the adsorption of hydrophobic groups of ionomer molecules at the surface of aqueous solution becomes more ordered. Under the same experimental conditions, the surface tension of anionic PU ionomer molecule appears to slightly decrease with increasing concentration of DMPA, as a result of slightly increased hydrophobic groups of ionomer molecule adsorbed at the surface of aqueous solution. The number average particle size of anionic PU ionomer molecule in aqueous solution appears to steadily increase with an increase in the concentration of DMPA or ES-200. This is because the intermolecular interaction between the ionomer molecules themselves as well as between the ionomer and water molecules, may increase the free volume of anionic PU ionomer molecule, thus causing the number average particle size of the ionomer molecules to increase. Experimental results indicate that both the tensile strength and the modulus of self-cured film of anionic PU ionomer molecule appear to decrease with increasing concentration of DMPA or ES-200, as a result of increasing of the intramolecular interactions and decreasing the intermolecular interactions. However, the elongation of self-cured film of anionic PU ionomer molecule is seen to increase with increasing concentration of DMPA or ES-200. This may be the result of weakening crosslinking due to strong intramolecular interaction of ionomer molecule. For the peel strength of self-cured film of anionic PU ionomer coated on the fabric (30% polyester/70% cotton), it has been found that the peel strength increases with increasing concentration of DMPA of ES-200, as a result of increased intermolecular interaction between ionomer molecules themselves. From the above mentioned experiment, the results show that ES-200 is better than DMPA in terms of number average particle size, tensil strength, elongation and peel strength. Accordingly, ES-200 is used as anionic monomer to synthesize water-soluble PANI/PU resin in the latter part of this study. A novel polyaniline-dodecyl benzenesulfonic acid/polyurethane (PANI-DBSA/PU) blend with very high dielectric constant (εr∼1120) has been developed in this work. This blend was prepared by in—situ polymerization of aniline in a well-dispersed aqueous solution of PU (ISP-blend). The dielectric constant of this blend increases with the content of PANI, and rises drastically as PANI-DBSA content exceeds 10 wt%. Similar PANI-DBSA/PU blends prepared by simple solution mixing method (SM-blend) shows no resemblance in the dielectric, conductive and thermal behaviors as compared to that of the ISP-blends. The dielectric behaviors of SM-blends are totally different from that of ISP-blends. The dielectric constant of SM-blends only increase a minor extent with PANI dopant, as compared to the dielectric constant of pure PU resin sample. It reveals that conductivities of SM-blends increase with the PANI added, while the conductivities of ISP-blends exhibit a percolation threshold of conductivity as the PAN content approaches 10 wt%. The data of experiment reveals very different that these two type of blends pass through discrete thermal degradation, such as the on-set deflection temperature, the temperature at 20 wt% loss, the temperature at 30 wt% loss and the % char yield at 600℃. The differences in the thermal behaviors exhibited by these two groups of blends demonstrate that their microstructures are different. These results also explain why different dielectric and conductivity properties were observed on these two types of blends. Significant different morphologies are observed by SEM for these two types of blends, i.e., a homogeneous structure was found in the ISP-blends, while an inhomogeneous phase segregated with PANI particulates was shown by the SM-blends. The ultra high dielectric constant exhibited by the ISP-blends is attributed mainly to the electrode polarization effect generated by the PANI component within the blend. In this study the new process of ISP-blends has been researched and developed, meanwhile an in-depth exploration and discussion on the property of ISP blends also have been made. The authors hope all the results of this paper can be served as useful reference in developing the advanced material for the industry and academic circles.