Miscibility and specific interactions in two polyelectrolyte/poly(2- ethyl-2-oxazoline) blend systems

Abstract

Poly(2-ethyl-2-oxazoline) (PEOx) was blended with the lithium or zinc salt of poly(styrenesulfonic acid) (PSSLi and PSSZn, respectively). Each PEOx/PSSLi blend showed the existence of two glass transition temperatures (T(g)s). The lower T(g) value is close to that of PEOx. The upper T(g) value is substantially lower than that of PSSLi, indicating that the two polymers do interact to a certain extent. The T(g)s of PSSZn and some PEOx/PSSZn blends could not be detected. A single T(g) was observed for PEOx/PSSZn blends containing 0.20 and 0.40 mole fraction of PSSZn, and the value is substantially higher than that of PEOx. PEOx/PSSZn blends are considered to be miscible. Fourier transform infrared spectroscopic measurements showed that both PSSLi and PSSZn interact with amide carbonyl oxygen atoms of PEOx. X-ray photoelectron spectroscopic studies showed the development of high- binding energy (BE) N1s peaks in all the PEOx/PSSZn blends but not in the PEOx/PSSLi blends. The interaction between Zn2+ and the carbonyl oxygen atom is so strong that there is an electron migration from the nitrogen atom to Zn2+ via the carbonyl group. Interaction between PEOx and PSSLi or PSSZn is also evidenced by the development of a low-BE S2p doublet in the blends. However, the Li1s and Zn2p peaks did not show significant changes upon blending the polyelectrolytes with PEOx. (C) 1999 Published by Elsevier Science Ltd.