Spectroscopic studies of interactions in complexes of poly(1-vinylimidazole) with poly(styrenesulfonic acid) or the zinc salt of poly(styrenesulfonate)

Poly(1-vinylimidazole) (PVI) forms complexes with poly(styrenesulfonic acid) and the zinc salt of poly(styrenesulfonate) (PSSA and PSSZn, respectively) in water/ethanol (2 : 1 v/v) solution, indicating the presence of strong interactions. Infrared spectroscopic measurements showed the existence of protonated imidazole groups in all the complexes. X-ray photoelectron spectroscopic studies showed the development of high-binding-energy N(1) 1s and N(3) 1s peaks, but the values of the binding energy shift of N(3) 1s are larger than those of N(1) 1s in all PVI/PSSA and PVI/PSSZn complexes, suggesting proton transfer from PSSA to imidazole N(3) atoms in the PVI/PSSA complexes, and coordination between Zn2+ and the imidazole N(3) atoms in the PVI/PSSZn complexes. Based on the values of the binding energy shift of the interacting nitrogen atoms, the strength of the coordination interaction in PVI/PSSZn complexes is weaker than the ionic interactions in the PVI/PSSA complexes. The development of a new S 2p spin-orbit split doublet at a low-binding-energy region reveals the existence of interactions between Zn2+ and the imidazole nitrogen atoms.