Characterization of complexes formed by mixing aqueous solutions of poly(2-ethyl-2-oxazoline) and poly(methacrylic acid) with a wide range of concentrations

Complexes were formed by mixing aqueous solutions of poly(2-ethyl-2-oxazoline) (PEOX) and poly(methacrylic acid) (PMAA) with a wide range of concentrations and were characterized with infrared and X-ray photoelectron spectroscopy, light scattering and intrinsic viscosity measurements. The infrared and X-ray photoelectron spectra indicated that PEOX and PMAA formed complexes by hydrogen bonds between the carbonyl groups in PEOX and the hydroxyl groups in PMAA but not between the nitrogen atoms in PEOX and the hydroxyl groups in PMAA. The results of light scattering and intrinsic viscosity measurements suggest that PEOX and PMAA first form complexes with high polymer chain density and that the complexes became large in size. The dependence of the precipitation concentration on the molecular weight of PEOX was also determined, and its unique dependence was discussed based on the experimental results.