Quenching copolymer fluorescence

Figure 11 shows Stern-Volmer plots for fluorescence quenching of the amphiphilic cationic copolymer QPh-x [74]. The quenching of QPh-x with MV2+ is expected to be much less effective than that of APh-x. The quenching data for the QPh-x system are presented in Table 3. For comparison, the data for a related... 

Similar data were reported by Turro et al., [62,63] who synthesized a copolymer of AA with 1.5 mol% of 2-[4-(l-pyrene)butanoyl]aminopropenoic acid, 19 and studied the fluorescence quenching with Tl +, Cu2+, and 1 ions in aqueous solution. 

When an electron-deficient BT unit was incorporated into the backbone of these polymers, an efficient energy transfer resulted in complete fluorescence quenching from the fluorene sites already at BT concentrations as low as 1% (for both neutral and quaternized copolymers, 377 and 378) [440] (Chart 2.93). These macromolecules emit green (544-550 nm, 377) to yellow (555-580 nm, 378) light and can be processed from environment-friendly solvents such as alcohols. The PLED fabricated with these polymers showed high 4>(]over 3 and 1% for 377 and 378, respectively (A1 cathode). 

For block copolymers with a polyacid or polybase block, the structure and properties of micellar solutions depend on the pH. For example, Morishima et al. (1982b) found that for a poly(9-vinylphenanthrene)-poly(methacrylic acid) (PVPT-PMA) diblock in water, the rate constant for the fluorescence quenching of phenanthrene groups by oxidative non-ionic quencher is pH dependent. These authors suggested that at low pH the polyacid units are not fully ionized and may participate in the formation of hydrophobic domains, cooperatively with PVPT. An alternative explanation is that the PM A chains are less solvated when... 

Almgren, M., J. Alsins, and P. Bahadur. 1991. Fluorescence quenching and excimer formation to probe the micellization of a poly(ethylene oxide)-poly(propylene oxde)-poly(ethylene oxide) block copolymer, as modulated by potassium uoride in aqueous solillHngmuir7 446—450. 

Dias FB, Maiti M, Hintschich SI, Monkman AP (2005) Intramolecular fluorescence quenching in luminescent copolymers containing fluorenone and fluorene units A direct measurement of intrachain exciton hopping rate. J Chem Phys 122(5) 054904... 

Dias FB, Knaapila M, Monkman AP, Burrows HD (2006) Fast and slow time regimes of fluorescence quenching in conjugated polyfluorene-fluorenone random copolymers The role of exciton hopping and dexter transfer along the polymer backbone. Macromolecules 39(4) 1598—1606... 

A method based on fluorescence quenching that did not depend on the nature of the transition was used to determine the micelle size of the hexyl copolymer (24). The basic idea underlying this method is that, in a solution containing luminescent probe and quencher molecules, both solubilized in an excess of micelles, the quenching will be inversely related to the number of micelles, because the more micelles there are, the smaller is the chance of both a probe and a quencher molecule inhabiting the same micelle (25-27). The hexyl copolymer used in our study had a degree of polymerization of 1700. The fluorescent probe was tris(2,2 -bipyridine)ruthenium(II) ion [Ru(bpy)3 ], the quencher was 9-methylanthracene (9-MeA), and the solvent was an aqueous 0.1 M LiCl solution. The fluorescence experiments were supplemented with solubilization experiments from these, the distribution of the 9-MeA between the polymer molecules and the solvent molecules, as well as the extent to which the polymer was in micellar form, could be simultaneously determined. The results indicated that the micelles inside the domain of a macromolecule encompassed approximately 24 repeat units, and that this micelle size was independent of the polymer concentration, of the probe concentration, and the extent to which the polymer was micellized. 

In the second group of monomers are 5-cyano-6-phenylnorbom-2-ene (Ueshima 1974) and ran5-5-carbomethoxy-6-ferrocenylnorbom-2-ene. In the latter case fluorescence quenching studies have been made as for the polymers and block copolymers derived from 81 (Albagli 1992b, 1993). 

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