Tuning of hydrophobicity of conducting films cast from polyaniline-phytic acid-poly(N-vinylpyrrolidone) dispersions
Abstract
Colloidal dispersions of polyaniline (PANI) doped by phytic acid (PA) and stabilized with poly(N-vinyl-pyrrolidone) (PVP) were prepared by oxidative polymerization of aniline and compared to the dispersions prepared under similar conditions in the absence of phytic acid. UV-vis and Raman spectroscopies confirmed the formation of protonated PANI in all the cases.
According to dynamic light scattering, the dispersions prepared in the presence of PA had a bigger average particle size (similar to 360 nm) compared to the PANI-HCl-PVP dispersions (similar to 300 nm). The long-term stability of all colloids was confirmed for up to 530 days.
The prepared dispersions were used for the film deposition by spiral bar technique resulting in transparent and uniform coatings, which consisted of spherical particles (110-200 nm). The highest conductivity values of 5 x 10(-3) and 7 x 10(-5) S cm(-1) for PANI-HCl-PVP and PANI-PA-PVP, respectively, were achieved at 1 wt% of PVP.
At 1 wt% of PVP, PANI-PA-PVP showed hydrophobic properties (theta=102 degrees), which decreased with increasing PVP content, while PANI-HCl-PVP had hydrophilic properties (theta=10 degrees) decreasing with increasing PVP fraction. Cyclic voltammetry of dropcast films showed that PANI-PA-PVP had significantly higher areal capacitance retention (97%) compared to PANI-HCl-PVP (61%).
Such conducting coatings with tunable surface characteristics can be useful for electrochemical applications.