Complexing properties and structural characteristics of thermally sensitive copolymers of N-vinylpyrrolidone and N-vinylcaprolactam

The interaction of thermally sensitive copolymers of N-vinylpyrrolidone (VP) and N-vinylcaprolactam (VC) with small molecules having different chemical structures (8-anilinonaphthalene-1-sulphonic acid magnesium salt dihydrate, acridine orange, phenol, and sodium dodecyl sulphate) in aqueous solutions was studied by luminescent methods. The interaction of these copolymers with acridine orange was studied at different temperatures. It was established that the complexing ability of VP–VC copolymers even at a low content of VC units exceeds that of poly-N-vinylpyrrolidone. At a high content of VC units, and a low content of VC units, the complexing ability of VP–VC copolymers was found to be higher than that of poly-N-vinylcaprolactam. It is shown that the change in functional characteristics of VP–VC copolymers is determined by changes in the structural organization of VP–VC macromolecules and by increasing intramacromolecular interactions between nonpolar groups. Intramacromolecular structurization occurring during temperature increase and complexation is manifested very distinctly by changes in nanosecond dynamics of macromolecules. Nanosecond relaxation times characterizing intramolecular mobility of macromolecules with increasing temperature and in complexation with phenol and surfactant ions were determined.