| The purpose of this study was to attempt to find an experimental approach for determining selected intrinsic properties of the conducting polymer, polyaniline, in its emeraldine oxidation state. It was found that optimization of solubility, molecular weight, molecular orientation, crystallinity, conductivity, tensile strength, swellability, etc. could be approached by specific chemical procedures and/or by processing the polymer into oriented fibers and films.; The most significant results and conclusions are as follows: (i) Chemical procedures were discovered for reversibly, chemically interconverting powders of the emeraldine base form of polyaniline between amorphous (soluble in N-methyl-pyrrolidinone, NMP) and partly crystalline (insoluble in NMP) forms. (ii) A "structure memory effect" was observed by x-ray studies during certain of the conversion/doping procedures. (iii) "As-synthesized" emeraldine base exhibited a unimodal gel permeation chromatographic (GPC) elution pattern in 0.5% (w/v) LiCl/NMP corresponding to M{dollar}sb{lcub}rm p{rcub} sim{dollar} 38,000, M{dollar}sb{lcub}rm n{rcub} sim{dollar} 26,000, M{dollar}sb{lcub}rm w{rcub} sim{dollar} 78,000 (polystyrene standard). GPC fractionalization of emeraldine base yielded molecular weights up to M{dollar}sb{lcub}rm p{rcub} sim{dollar} 320,000, M{dollar}sb{lcub}rm n{rcub} sim{dollar}, 260,000 and M{dollar}sb{lcub}rm w{rcub} sim{dollar} 380,000, the highest molecular weights known for polyaniline at the time the studies were performed. (iv) The conductivity of the (HCI-doped, compressed pellet powder) polymer increases linearly with molecular weight up to {dollar}sim{dollar}16 S/cm and then exhibits little dependence on molecular weight. (v) Emeraldine base can be processed into highly crystalline fibers, which remain crystalline after doping. The polymer chains show significant alignment even in amorphous regions. (vi) The conductivity of the aligned fibers increases (up to {dollar}sim{dollar}170 S/cm) with draw ratio and degree of crystallinity. (vii) The tensile strengths of undoped ({dollar}sim{dollar}318 MPa) and doped ({dollar}sim{dollar}150 MPa) fibers approach the lower limits of those observed for some conventional commercial polymers. (viii) Emeraldine base gels which show reversible "shape memory" properties have been prepared and studied. |
