| The purpose of the present study was to investigate factors responsible for controlling the electronic and morphological properties of polyaniline (emeraldine oxidation state) films. This was accomplished by studying (i) the nature of the solutions from which the films were cast and the extent to which they affected the properties of the films, and also by studying (ii) in-situ deposited films formed on substrates from aqueous polymerizing solutions of aniline.; The most significant results are: (1) As-synthesized emeraldine base produced by the standard synthetic method, is significantly aggregated by hydrogen bonding between the amine and imine nitrogen sites. A decrease of the imine nitrogen fraction by reduction of emeraldine base, EB, significantly decreases hydrogen bonding and aggregation of EB in N-methyl-2-pyrrolidinone (NMP) solution. NMP, LiCl and poly(dimethylsiloxane) copolymer also significantly decrease hydrogen bonding in EB. (2) Properties of polyaniline films are highly dependent on the nature of the solutions from which films are cast. Films cast from a dilute solution where polymer chains are less aggregated tended to be partly crystalline and exhibit high conductivity after doping with HCl, whereas films cast from concentrated solutions where polymer chains are more aggregated are more disordered and exhibit low conductivity. (3) In-situ deposited EB-I films (which have never been in contact with any organic liquid or vapor) exist in "coil-like" molecular conformation. Exposure to NMP,THF and m-cresol vapors promotes an expanded "coil" conformation, whereas exposure to methanol, benzyl alcohol and chloroform results in no change in the existing "coil-like" molecular conformation. (4) Thin in-situ deposited films and powder of chiral polyaniline were chemically synthesized in the presence of chiral dopants such as (1S)-(+) and (1R)-({dollar}-{dollar}) camphorsulfonic acid. The backbone of polyaniline was found to be chiral as evidenced by retention of chirality after removal of the chiral dopant. |
