I'm searching for a solvent in which polyaniline is completely soluble. Do you have any suggestions?
It depends on the molecular weigth: n-methyl pirrolidone is good. For low molecular weigth you can try dimethylformamide, isopropanol dmso, etc
Solubility of polyaniline can be described by the 3 Hansen solubility parameters (HSPs)Dispersion (D), the nonpolar interactions
Polarity (P), the permanent dipole molecular interactions
Hydrogen bonding (H), electron interchange molecular interactions.
I estimated the HSPs for the -[Ph-N=Phenylene=N-]- unit as representative for polyaniline to Dispersion 19,5 Polarity 4,1 Hydrogen bonding 0,0 [MPa½ ]. Relative solubilities of polyaniline in different solvents can be ranked according to the solvent/polyaniline distance in the HSP space, where good solvents have short distance to polyaniline. The closest single solvents were o-dichlorobenzene, chlorobenzene, toluene, trichloroetylene, ethylbenzene with distances of 3,5 to 5. The best 2 solvent system would be ethylbenzene/propylene carbonate = 78/22 vol% with a distance of 3,2. The best 3 solvent blend would be ethylbenzene/o-dichlorobenzene/propylene carbonate = 54/33/13 vol% with a distance of 3,1. On a confidential basis such solubilty information is available under the link below.
http://confidentsolventselection.com/about/confident-solvent-selection.html
High quality, freestanding films of undoped PAni may be cast from NMP (N-methyl-2-pyrrolidone), as Silas Derenzo said, however, removing NMP from the film / membrane requires a relatively long (up to several days) period of vacuum drying or purging with inert gas.
When using other solvents, care needs to be taken not to evaporate them (and, hence, precipitate PAni) too rapidly, as this will wreak havoc with the mechanical properties of the films.
Take emeraldine base (EB or Polyaniline base), stir with m-cresol for 12h at room temperature. You will get green solution and cast in a teflon plate, keep in vacuum oven at 80°C for 12h. You will get film (but not flexible). m-cresol acts as secondary dopant and solvent for polyaniline. You may add some organic dopants after EB dissolves completely in the m-cresol. ( m-cresol is toxic to kidneys, lungs, liver, skin and central nervous system).
Dear Shumaila, how to get the film of Polyaniline by using polyaniline powder (EB)? Did you get the best way? Thank you.
Dear Weike Wang
Yes i have got the method for the preparation of poyaniline film (EB powder) by using NMP (N-methyl-2-pyrrolidone) to get self supporting films of EB as suggested by Sir Silas Derenzo and Hanno priebe.
In addition m-cresol may also be used as solvent. The details of the procedure have been provided by Sir Amarnath C. Anbalagan in the above dicussion.
wishes
Dimethylformamide (DMF) could be a good solvent to dissolve polyaniline.
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