We have carefully examined the possible role of local oscillator coupling in D2O(or H2O), and locally concentrated evanescent electric fields in creating a large intensity perturbation of the v(OD) band of water in the polyelectrolytes SPEES/PES (S-5, S-8 and S2O). Isotopic dilution experiments lead to the same (or higher) extinction coefficient while an ATR/transmission experimental comparison also gives a similar intensity. We conclude that neither effect is responsible for enhanced P values, and that these must be caused by strong polymer-water interactions at the anionic SO3- groups on these polymers. (C) 2003 Elsevier Science Ltd. All rights reserved.