Homogeneous fluorescent labeling of cationic polyacrylamides

A number of fluorescently labeled polymers have already been prepared. Since these polymers have usually been synthesized by copolymerization, the distribution of fluorescent groups will in such a case be heterogeneous because monomers always have different reactivity ratios. In this article, the preparation of fluorescently labeled cationic polyacrylamides (C‐PAM) with homogeneous distributions of both fluorescent and cationic groups is described. Four fluorescently labeled C‐PAM with isoindol, pyrene, anthracene, and dansyl groups were prepared in the homogeneous reaction system. These polymers were water soluble. Their wavelengths for maximum emission were in order of the above 380, 382 (smaller peak at 400), 435, and 540 nm, which thus covered a wide wavelength range. It is noteworthy that C‐PAM with pyrene and anthracene groups have little fluorescence intensity at 540 nm, which is the maximum emission wavelength for C‐PAM with dansyl group, making an accurate determination of the two polymers in the same solution possible. Even at the low degree of labeling, the detection limit of polymers is very low (approximately 1 ppm). © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 672–675, 2002