Abstract
Owing to its unique electrooptical and magnetic properties, conducting polymer is one of the recent focuses in the field of material research. Polyanilines have been demonstrated to be particularly useful in many applications, such as biosensors, lightemitting diodes, molecular devices, conducting photoresists, optical switches, smart windows, transistors, rechargeable battery, and anticorrosion. For most of the applications, the conducting ability of polyaniline is one of the important and key properties. A fast, simple, and environmentally friendly new electrochemical method for enhancing the conductivity of a preformed polyaniline film has been found in this dissertation. Utilizing this method of electrochemical forcing pretreatment at a certain effective voltage, a polyaniline solid matrix can be made more conductive. For example, the conductivity of a preformed polyaniline film (as thick as 10 □m) can be easily enhanced by about an order of magnitude within a pretreatment time of only ca. 5 min. The UV-vis-NIR and ESR spectroscopic evidences indicated that the charge carriers in the polyaniline matrix are more delocalized after such electrochemical pretreatments. The results of CV studies indicated that the resultant polyaniline film has higher charge transport efficiency and a greater redox rate. Such phenomenon may be linked with a possible backbone conformational change, as induced by this novel electrochemical pretreatment, within the solid matrix of polyaniline film. The discovery of this novel electrochemical method opens up a new dimension for controlling and/or enhancing the conductivity of polyaniline, which are critical for many practical applications of conducting polymers. Highly conductive new aniline copolymers containing alkylthio substituent have been first prepared from unsubstituted polyaniline, utilizing a concurrent reduction and substitution reaction performed in the solid-state matrix of polyaniline. The resultant copolymer film after one reaction treatment cycle was found to contain ca. 30 - 40 mol% of alkylthio group, and was as conductive (3 - 10 S/cm) as its parent polyaniline film (2-3 S/cm). All these new butylthioaniline copolymers are highly soluble in THF, dioxane, 2-methoxyethylether and 2-methoxyethanol, which are non-solvents for the parent polyaniline. Since the molecular weights of these aniline copolymers are higher than their parent unsubstituted polyaniline, the enhanced solubility in THF and other organic solvents is mainly contributed by the solubility parameter change of the resulted copolymers causing by the substitution of alkylthio group. Compared to their alkoxy analogues, e.g. poly(butoxyaniline) (2 x 10-3 S/cm) and poly(dibutoxyaniline) (7 x 10-4 S/cm), the unusual high conductivity of these new alkylthio-containing aniline copolymers in combination with their good solubility in THF and other common organic solvents is especially worth to note. The results suggest that the concurrent reduction and substitution route is a better way, as compared with the conventional copolymerization method, for preparing aniline copolymers with a more conjugated and regular backbone structure.