Binding of butyl orange by poly(2‐dimethylaminoethyl methacrylate) and copolymers of 2‐dimethylaminoethyl methacrylate and N‐vinyl‐2‐pyrrolidone: Peculiar temperature dependence of the binding

Abstract

The temperature dependence of the binding of butyl orange by a homopolymer of 2‐dimethylaminoethyl methacrylate (DMAEMA) and copolymers of DMAEMA and N‐vinyl‐2‐pyrrolidone (VPy) has been examined at various pH's. The binding is very much dependent upon the temperature of the system, the pH of the binding medium, and the DMAEMA content in the polymer. In this case maximal binding is obtained at approximately 15–25° in the temperature range measured, although in most cases which have been examined, the degree of binding increases steadily with increasing temperature. This peculiar temperature dependence of the binding becomes more pronounced as the pH and the DMAEMA content are increased. The appearance of the peculiarity is discussed in terms of the pH‐induced conformational changes of the polymer and the hydrophobicity of the polymer.

Fluorescence studies of pyrene-labelled, pH-responsive diblock copolymer micelles in aqueous solution

“…Clearly, ht f i decreases monotonously with increasing pH, from 127.8 ns to 70.5 ns. This is contrary to expectation: previous fluorescence measurements using a methyl orange probe confirmed [54] that the homopolymer, PDMA, changes from an extended structure at low pH to a compact coil at high pH [55,56]. From our experience of the conformational behaviour of smart polymers using a pyrene probe [8,15,49,50], and with reference to the literature [1,4,6], it was expected that the fluorescence lifetime of the label should increase assuming that the DMA component induces a chain collapse in the block copolymer.…”

Binding of methyl orange or ethyl orange dyes by some dioxolane copolymers: Synthesis of the copolymers and thermodynamics of the dye–copolymer interactions

“…Many investigations have been carried out to elucidate the energetic characteristics of these interactions and the binding of small molecules by macromolecules 2, 7, 10, 19. The relationship between the amount of bound‐dye and the binding constant is generally evaluated from the double reciprocal plots for the bound‐dye vs free dye, i.e., the Klotz plot of 1/ r vs 1/ C , as follows:2, 5, 10 where k refers to the intrinsic binding constant, n is the number of the binding sites per 10 5 g of the polymer. The first binding constant K is defined as K = nk , and it is generally used for the quantitative comparison of the binding capacities of the macromolecules.…”

“…Water‐soluble synthetic polymers containing suitable apolar and ionic side chains exhibit strong affinities to bind small molecules 1–5. Stochiometric or energetic characteristics of the binding interactions were examined particularly by the equilibrium dialysis method 2, 6–9.…”

Optical Properties of Polyelectrolytes

“…Corroborative evidence that PDMAEMA undergoes a change in conformation has resulted from fluorescence spectroscopic measurements using several water-soluble probes dispersed in aqueous solutions of the polyelectrolyte [151,155,156]. At low pH [50,151], mutual repulsion between the positive charges in the protonated form induces expansion of the coil.…”