An NMR investigation of the interaction of polyethylene oxide with water-soluble poly(vinyl phenol-co-potassium styrene sulfonate)

The water-soluble complex of polyethylene oxide (PEO) with poly (vinyl phen ol-co-potassium styrene sulfonate) (PVPh-co-KSS) was studied by liquid-stat e NMR. PEO showed two peaks in the H-1 spectra, which corresponded to the f ree and complexed PEG. The ratio of the free PEO/complexed PEO was decrease d with the increase in the mixing ratio of PVPh-co-KSS/PEO. Some of the com plex formation disappeared when the pH was raised from 6.4 to 12.0. It had been thought that at high pH, the phenolic groups dissociate and thus canno t form hydrogen bonds. The fact that NMR indicates some interaction at pH 1 2.0 implies there are some other interactions, such as hydrophobic interact ions between the aromatic rings and the polyether methylene groups, contrib uting to PEO and PVPh-co-KSS complex formation. Nuclear Overhauser effect ( NOE) cross peaks were observed between PEO and the aromatic protons of PVPh -co-KSS in nuclear Overhauser effect spectra (NOESY) suggesting that the di stance between PEO and the aromatic protons of PVPh-co-KSS was less than 5 Angstrom. The exchange between the complexed PEO and the free PEO was slow on the NMR time scale. The ratio of the integral of the complexed PEO to th e free PEO increased with temperature, indicating that the number of PEO se gments interacting with the aromatic ring increases with temperature. (C) 2 000 John Wiley & Sons, Inc.