Binding of methyl orange and its homologs by powdered nylon 612: Peculiar temperature dependence on the binding

Abstract

The ability of powdered Nylon 612 to bind methyl orange, ethyl orange, propyl orange, and butyl orange was investigated at 5, 15, 25 and 35°C in an aqueous solution. The amount of binding of the dye is much higher with this polyamide than with powdered Nylon 66 reported previously,1 although the former polymer has fewer amide end groups. The Van't Hoff plots of the first binding constant for the binding of butyl orange and propyl orange by powdered Nylon 612 exhibit a bell‐shaped curve, whereas the plots for methyl orange and ethyl orange do not. Maximal binding occurs at approximately 15°C for propyl orange and at about 25°C for butyl orange. This is the first instance where the peculiar temperature dependence of the binding constant has been found in the binding of propyl orange, whose hydrophobicity is less than that of butyl orange. These tendencies can be accounted for in terms of increased hydrophobic of butyl orange. These tendencies can be accounted for in terms of increased hydrophobic domains in powdered Nylon 612 and enhanced hydrophobic contributions in the binding process.

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

“…This suggests that the entropy change, during the formation of the dye–copolymer complex, more favorable for the binding. This result is in accord with the earlier observations given in the literature 2, 7, 10…”

“…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.…”

“…The literature data indicate that, if the enthalpy of the interactions is exothermic at a temperature while it is endothermic at other temperatures, the temperature dependence of the binding is not regular. Such situations are generally observed when both or either of the binding entities are sufficiently hydrophobic, and strong interactions are involved in the binding process 7, 10…”

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

“…The binding isotherms of P-I1 at pHs 7, 8 approaches a plateau with further decreasing temperature (Fig. 4).…”

“…The amount of binding decreases in the following order: '15 > 5 > 25 > 35°C at pH 8 and 15 --25 > 35 > 5 at pH 9. Figures 7,8,and 9 show the extent of binding of butyl orange by P-I11 at pH's 7, 8, and 9, respectively. The binding curves of P-I11 at pH 7 follow a general pattern in that the degree of binding increases monotonically with decreasing temperature (Fig.…”