Polyaniline dispersions. 2. UV-Vis absorption spectra
- ISSN: 03796779
- DOI: 10.1016/0379-6779(93)91266-5
Abstract
Optical absorption spectra of polyaniline dispersions in aq. media have been investigated. Two absorption bands located at 340 and 610 nm are found for blue polyaniline base in ammonia solns. The spectra of alkalized dispersions are close to those obsd. for polyaniline base in N-methylpyrrolidone soln. (max. at 332 and 638 nm), but the position of the max. depends on the nature of the alkali. In the acidic region, three distinct absorption bands of the green protonated polyaniline are obsd. at 350, 430 and 810 nm. The spectroscopic response to change of pH is fast but addnl. slow changes occur and may extend for hours when close to neutral media. The absorption coeff. of polyaniline in 1 M hydrochloric acid for a local max. between 380 and 420 nm is estd. as e = 31 500+-1700 cm2 per g of polyaniline hydrochloride. Spectroscopy is used to follow up the dispersion polymn. of aniline. After an induction period, a fast polymn. takes place and the originally colorless soln. turns blue. A subsequent change of color to green indicates termination of polymn.
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