An NMR Investigation of the Interaction of Polyethylene Oxide with Water-Soluble Poly(vinyl phenol-co-potassium styrene sulfonate) RONGJUAN CONG, 1 ALEX D. BAIN, 2 ROBERT PELTON 1 1 McMaster Centre for Pulp & Paper Research, Department of Chemical Engineering, McMaster University, Hamilton, Ontario L8S 4L7, Canada 2 Chemistry Department, McMaster University, Hamilton, Ontario L8S 4L7, Canada Received 3 September 1999; revised 9 February 2000; accepted 10 February 2000 ABSTRACT: The water-soluble complex of polyethylene oxide (PEO) with poly (vinyl phenol-co-potassium styrene sulfonate) (PVPh-co-KSS) was studied by liquid-state NMR. PEO showed two peaks in the 1 H spectra, which corresponded to the free and complexed PEO. The ratio of the free PEO/complexed PEO was decreased with the increase in the mixing ratio of PVPh-co-KSS/PEO. Some of the complex 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 cannot form hydrogen bonds. The fact that NMR indicates some interaction at pH 12.0 implies there are some other interactions, such as hydrophobic interactions between the aromatic rings and the polyether meth- ylene groups, contributing 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 distance between PEO and the aromatic protons of PVPh-co-KSS was less than 5 Å. 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 the free PEO increased with temperature, indicating that the number of PEO segments interacting with the aro- matic ring increases with temperature. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1276 –1284, 2000 Keywords: PEO cofactor interactions; flocculation; hydrogen-bonding complexes; phenolic complexes; polyether complexes INTRODUCTION Very high molecular weight (i.e., greater than 10 6 Dalton) polyethylene oxide is a fascinating mate- rial, which has been used widely in a variety of applications. 1 In the 1970s, it was shown that PEO, when used in conjunction with some water- borne phenolic polymers called cofactors, is an effective colloidal flocculant in paper-making ap- plications. 2,3 This technology has been practiced since 1980 and many flocculation studies have been published, which give indirect information about the aqueous complex formed by PEO and the phenolic cofactor. On the other hand, there are few details known about the structure and properties of the complex mainly because com- mercial cofactors are complicated mixtures of structures formed by condensation polymeriza- tion. 4 Furthermore, the flocculants are used in the ppm concentration range, which complicates the in situ determination of complex structure. This work describes the use of NMR to give direct Correspondence to: R. Pelton (E-mail: peltonrh@mcmaster.ca) Journal of Polymer Science: Part B: Polymer Physics, Vol. 38, 1276 –1284 (2000) © 2000 John Wiley & Sons, Inc. 1276