Interaction of 1-pyrenebutyrate with poly(vinylbenzo-18-crown-6) and poly(vinylbenzoglyme) in water

Binding constants of 1-pyrenebutyrate (PB^?, 1-pyrenecarboxylate and 1-pyrenevaleriate to the polysoap-type macromolecule poly(vinylbenzo-18-crown-6) (P18C6) and the poly(vinylbenzoglyme) PVBG (a polystyrene with two CH₃O(CH₂CH₂O)₂-substituents at the 3 and 4 position of each benzene ring) were determined spectrophotometrically (λ_m 342 nm for free PB^?, 348 nm for polymer-bound PB^?). The binding appears to follow Langmuir adsorption behaviour. Interaction with P18C6 is enhanced on adding crown ether-complexable cations, which converts the neutral polymer into a polycation. The enhanced binding is chiefly caused by lower values of $\text{1}\text{n}$ (minimum number of crown monomer units per bound PB^? molecule). This decreases at 25°C from $\text{1}\text{n}\text{= 25}$, for neutral P18C6, to 6.2 and 2.7 in the presence of 0.01 M CsCl and 0.1 M KCl, respectively. It is argued that the COO^? substituent of bound PB^? is probably located in the aqueous layer at the polymer-water interphase. Its presence close to the crown ligands enhances the binding of K⁺ or Cs⁺ cations to these ligands by forming crown-complexed ion pairs PB^?, M⁺ … P18C6. The typical excimer fluorescence emission peak of PB^? is observed when P18C6 in 0.1 M KCl is saturated with PB^?. Some of the binding measurements were carried out in ethanol-water mixtures.