Fluorescence Studies of Self-Assembly in Aqueous Solutions of Poly(ethylene-co-methacrylic acid) Ionomers

Abstract

Steady-state and time-resolved fluorescence measurements were performed on aqueous solutions of poly(ethylene-co-methacrylic acid) (EMAA) ionomers using pyrene (P) and 1,3-bis(1-pyrenyl) propane (P3P) as the luminophores and the nitroxide radical 5-doxylstearic acid methyl ester (5DSE) as the fluorescence quencher. The ionomers contained 7.5 mol % methacrylic acid and were neutralized (90%) with KOH. The fluorescence spectra of P and P3P together with the electron spin resonance (ESR) spectra of 5DSE indicate that all probes are located in an environment of low polarity and high viscosity that was identified as the hydrophobic micellar core of EMAA aggregates. The local polarity was estimated from the intensity ratio of the third to the first vibronic peaks (I III /I I) in the fluorescence spectrum of P. The critical micelle concentration (CMC) of the ionomer, CMC = 0.02% (w/w) EMAA, was deduced from the dependence of I III /I I on the ionomer concentration. The spectroscopic data (ESR and fluorescence) point to the existence, below the CMC, of intramolecular (unimeric) micelles, which are in equilibrium with large aggregates above the CMC. The microviscosity of the micellar core, η, was estimated to be ≥230 cP at ambient temperature on the basis of the fluorescence spectra of P3P, from a calibration curve of the intensity ratio of the excimer to monomer emissions, I E /I M, vs viscosity in 14 nonaqueous solvents of known viscosities. The fluorescence decay of P in EMAA in the presence of 5DSE as the quencher was analyzed with two kinetic models, the Infelta−Tachiya model based on a Poisson distribution of the quencher and the luminophore in the micelles and the general approach of dispersive kinetics that introduced the time-dependent rate coefficient, k qm, for intramicellar quenching. The second model gives a better fit to the experimental data, and the low value of the dispersive parameter, α = 0.30 (compared to unity for classical kinetics), indicates a broad distribution of the quenching rate constants. The results obtained in this study add important structural details to the recent models for self-assembly of EMAA ionomers, which were deduced from spin probe ESR spectroscopy and small-angle neutron scattering.

Elastomeric azo-polyurethanes containing fluorescent pyrene and their photo activity

“…Such result can be explained in terms of hydrophilic aggregation due to the physical cross-linking encountered in the ionic polyurethanes, even in very dilute DMF solution of AzPUC-Py1. A similar behavior was observed in the study of perfluorinated ionomers (PFI) having sulfonic groups [22].…”

Quenching Mechanisms and Diffusional Pathways in Micellar Systems Unravelled by Time‐Resolved Magnetic‐Field Effects

“…Apart from their fundamental difference, that is, their opposite surface charge, SDS and DTAC micelles are remarkably alike; above all, they have very similar microviscosities (19 versus 18 cP) [21] and micellar radii (17.5 versus 17 ). [22,23] To match the starting conditions of the photoreactions as closely as possible, the same bulk concentration of A was used, and the occupation numbers were made identical, which only requires a slight decrease of the surfactant concentration in the case of DTAC.…”

Synthesis and Fluorescence Spectrum of N, N' Bis (2-Hydroxy Benzylidene) Benzidine with Different Solvents and Different PH

“…Finally, it decreases up to pH=10. The finest value for the fluorescence amount of PH (6), this mean that quantum yield was very good at this point. …”

“…Fluorescence is a strong implement for examining the construction and dynamics of substance or active systems at a molecular field. Solid surfaces, Polymers, proteins, liquid of surfactants, organic membranes, nuclei acids and organism cells are famous samples of systems in which assessment of the factors like polarity, instruction, liquids, electrical potential and molecular mobility is conceivable by incomes fluorescent molecules taking the role of sensors [6,7,8]. The many applications of fluorescence compounds confirm the requirement for an account of the fluorescence (2-Hydroxy Benzylidene) Benzidine with Different Solvents and Different PH characteristics of this molecule in a liquid solution.…”