Poly fluorescence probe studies

Interpolymer complexation between water-soluble polymers by hydrogen bonding was a frontier subject in the 1970s. Polyfcarboxylic acids), mainly po-lyfacryhc acid) (PAA) and poly( methacryflc acid) (PMAA), served as the most common proton-donating components. As for the proton-accepting polymers, poly(ethylene oxide ) (PEO or PEG) and poly(M-vinyl-2-pyrrolidone) (PVPo) were often used. The important results on the formation of complex aggregates and its dependence on the structur prameters have been reviewed [2,3,8]. In this section we select a few representative topics to look at recent advances in interpolymer complexes in aqueous media, with the emphasis on fluorescence probe studies. 

J. S. Royal, J. G. Victor, and J. M. Torkelson, Photochromic and fluorescent probe studies in glassy polymer matrices. 4. Effects ofphysical aging on poly(methyl methacrylate) as sensed by a size distribution of photochromic probes, Macromolecules 25, 729-734 (1992). 

Wilhelm M, Zhao C-L, Wang Y, Xu R, Winnik R-A. Poly(styr-ene-ethylene oxide) block copolymer micelle formation in water A fluorescence probe study. Macromolecules 1991 24 1033-1040. 

Wilhelm M, Zhao CL, Wang YC, Xu RL, Winnik MA, Mura JL, Riess G, Croucher MD (1991) Polymer micelle formation. 3. Poly(styrene-ethylene oxide) block copolymer micelles formation in water—a fluorescence probe study. Macromolecules 24 1033-1040... 

Fluorescence Probe Studies of Poly(acryIic acid) Interchain Complexation Induced by High Shear Flow and Influence of Cationic Surfactants on the Complexation... 

Fluorescence Probe Studies of Poly (acrylic acid) Interchain Complexation... 

A detailed study of the structure of the aggregates of the ionic surfactants in polyelectrolyte networks was presented in Refs. [66,68]. The dynamics of the changes in the microenvironment of the fluorescent probe, pyrene, in slightly crosslinked networks of poly(diallyldimethylammonium bromide) (PDADMAB) during diffusion of sodium dodecyl sulfate (SDS) in the gel phase has been investigated by means of fluorescence spectroscopy. In Ref. [66], an analogous investigation was reported for complexes formal by the sodium salt of PMAA with cetyltrimethylammonium bromide (CTAB). 

Time-resolved fluorescence spectroscopy and fluorescence anisotropy measurements have been applied to study (i) excimer formation and energy transfer in solutions of poly(acenaphthalene) (PACE) and poly(2-naphthyl methacrylate) (P2NMA) and (ii) the conformational dynamics of poly(methacrylic acid) (PMA) and poly (acrylic acid) as a function of solution pH. For PACE and P2NMA, analysis of projections in which the spectral, temporal and intensity information are simultaneously displayed have been used to re-examine kinetic models proposed to account for the complex fluorescence decay behaviour that is observed. Time-resolved fluorescence anisotropy measuranents of fluorescent probes incorporated in PMA have led to the proposal of a "connected cluster" model for the hypercoiled conformation of this polymer existing at low pH. 

A further application of time-resolved fluorescence measurements is in the study of conformational dynamics of polymer chains in solution. Fluorescence anisotropy measurements of macromolecules incorporating suitable fluorescent probes can give details of chain mobility and polymer conformation (2,14). A particular example studied in this laboratory is the conformational changes which occur in aqueous solutions of polyelectrolytes as the solution pH is varied (15,16). Poly(methacrylic acid) (PMA) is known to exist in a compact hypercoiled conformation at low pH but undergoes a transition to a more extended conformation at a degree of neutralization (a) of 0.2 to 0.3 (1 6). Similar conformational transitions are known to occur in biopolymer systems and consequently there is considerable interest in understanding the nature of the structures present in model synthetic polyelectrolyte solutions. 

The majority of studies aim at labelling of polysoaps, to study their behaviour as discussed in Sects. 3 and 4. UV/visible-probes, fluorescence probes and ESR probes have been attached. For example azo dyes were used as labels taking advantage of their trans-cis photoisomerization [203, 217, 260], More frequently fluorescent labels have been fixed such as dansyl [174,175,177,287], naphthyl [211, 259], anthracenyl [183, 189] or pyrenyl groups [204, 259], For ESR studies, e.g. nitroxy labelled polysoaps based on poly(ethyleneimine) are described [145]. 

Photophysical studies on a conformational transition of PMA induced by cationic surfactants have been reported (7). The stretched PMA chain at pH 8 collapses on addition of cationic surfactants that is, the hydrophobic interactions between the cationic surfactants that are bonded to the PMA chain lead to refolding of the polymer chain, and thus provide a hydrophobic site for fluorescence probes at pH 8. The cationic polyelectrolyte poly(4-vinylpyridine) quatemized with n-dodecyl bromide (8 i0) or hexadecyl bromide (11) are also examples of hydrophobically modified polyelectrolytes. 

Fluorescence studies 14, 15) using pyrene, pyrene derivatives, and cationic probes in poly(methacrylic acid) have shown that a conformational transition from a closed compact coil to extended form induced by pH is a progressive process over several pH units (pH 4-6). The emission spectrum of 4 X 10 M R6G and 4 X 10 M RB excited at 480 nm in water is not dependent on pH. However, in aqueous solutions of PM A, the spectra are significantly dependent on pH (shown in Figure 6). At pH 4-5, the spectra are similar to the typical emission of RB at pH 2-3 and 6-7, the spectra in PMA display stronger emission at 550 nm and at pH 8, the spectra are identical to those in water. 

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