PANI-HCSA cast from different solvents

A. Thin Films of PANI-HCSA Cast from Different Solvents... 

Only two different UV-vis-NIR spectra were observed for solutions of HCSA fully doped PANI-ES in different solvents. The first type of spectrum (Fig. 3a), which was obtained from solutions in chloroform, NMP, DMF, and benzyl alcohol, had three distinctive absorption peaks at 360 nm (3.42 eV), 440 nm (2.80 eV), and 780 nm (1.58 eV), respectively. These polymer solutions ( 2% w/w) were green in color and were not viscous. Freestanding films cast from these solutions were very brittle with conductivities in the range 0.01-0.1 S/cm. The second type of spectrum (Fig. 3b), which was obtained for solutions in /n-cresol, p-cresol, 2-chlorophenol, 2-fluorophenol, and 3-ethylphenol, had an absorption peak at —440 nm (2.80 eV) and a steadily increasing free carrier tail from 10()0 nm to the IR region. Note that the free carrier tail in the IR region is characteristics of metallic conductive materials such as metals, iodine-doped polyacetylenes, and AsFj-doped poly(/>-... 

Functionalized protonic acids such as ( ) camphor sulfonic acid (HCSA) and dodecyl benzene sulfonic acid (HDBSA) are used as primary dopants while m-cresol, xylene, etc. are used as the secondary dopants. The free-standing non-oriented PANI-CSA films cast from the above solvents have conductivities in the range 100—400 S cm , a value two orders of magnitude larger than that of non-oriented films of emeraldine base doped with aqueous HCl. MacDiarmid et al. [34] found that the conductivity of POT-CSA is 0.2 S cm in w-cresol and 2 S cm in chloroform whereas that of PANI-CSA is 140 S cm in w-cresol and 0.16 S cm in chloroform. These differences can be attributed as due to the interaction of the non-polar covalent methyl groups in POT with less polar chloroform, whereas in the case of RANI, the polar backbone can interact more readily with the polar /n-cresol. 

---