Showing papers by "Younan Xia published in 1994"

Camphorsulfonic Acid Fully Doped Polyaniline Emeraldine Salt: In situ Observation of Electronic and Conformational Changes Induced by Organic Vapors by an Ultraviolet/Visible/Near-Infrared Spectroscopic Method

Abstract: It is shown that thin films of camphorsulphonic acid-doped polyaniline spun from chloroform or NMP have a coil-like conformation and shorter conjugation length while those films spun from m-cresol have an expanded coil-like conformation and longer conjugation length. The coil-like conformation can be irreversibly converted to the expanded coil-like conformation by exposure to m-cresol vapor at room temperature

Vapor phase "secondary doping" of polyaniline

Abstract: A dramatic change occurs in the electronic spectrum of a thin (solid) film of polyaniline doped with the “primary dopant,” d,l-camphorsulfonic acid (spun from its solution in chloroform on to a quartz plate) when it is exposed to the vapor of the “secondary dopant” m-cresol, at room temperature. The resistance decreases by a factor of > 102 and it becomes insoluble in chloroform due to an increase in its crystallinity. The localized polaron absorption at 780 nm is replaced by a very intense free carrier tail commencing at ≈ 1000 nm and increasing steadily in intensity to ≈ 2600 nm, which is consistent with delocalized electrons in the polaron band. “Secondary doping” with a variety of substituted phenols and a number of different “primary” protonic acid dopants is observed.

Methods for preparing conductive polyanilines

Abstract: Methods for preparing conductive polyaniline forms are provided in which the conductivity of the polyaniline form can be substantially increased by contacting the polyaniline form with a phenolic compound that acts as a secondary dopant for the polyaniline. Generally, a doped polyaniline solution is prepared in which the polyaniline is initially doped by a protonic acid and a doped polyaniline form is then prepared from this solution. The polyaniline form can then be contacted with the phenolic compound in either its vapor or liquid state, however it is preferred that the polyaniline form be maintained in either the gelatinous or solid state during the contacting step. The conductivity of the polyaniline form can be raised by a factor of up to about 500-1000.