An ESR study of polymer‐Cu(II) complexes in poly(vinyl alcohol), polyacrylamide, and poly(vinyl pyrrolidone) films

Optical and ESR spectra of polymer‐Cu(II) complexes in polymer films have been studied. The dependence on F 1 = [Cu 2+ ]/[ MU ] and F 2 = [OH − ]/[Cu 2+ ], where [ MU ] is the molar concentration of monomeric units of the polymer, has been obtained. Optical spectra and potentiometric titration curves in solution have also been studied. There exists a buffer region 0 ≲ F 2 ≲ 2. Optical spectra in films are slightly different from those in solutions. At least five different ESR signals, designated as A , B , C or D , and E , have been found in poly(vinyl alcohol)‐Cu(II). These signals appear successively with increasing F 2 . Assignments are proposed as follows. Signal A ( F 2 ≈ 0), also found in poly(acrylamide)‐Cu(II) and poly(vinyl pyrrolidone)‐Cu(II), is due to a single Cu(II) coordinated with two water molecules and chelated with two oxygens or nitrogens attached to the polymer. A chain of Cu(II) ions singly and double bridged with OH − ions is responsible for the B signal ( F 2 ≈ 1). The C and D signals ( F 2 ≈ 2) appear to be caused, respectively, by a dimeric Cu(II) complex singly or doubly bridged with OH − ions. The E signal ( F 2 ≈ 7) appears to be due to a monomeric Cu(II) complex, different from that responsible for the A signal.