We studied interactions of water with OH groups in poly(ethylene-co-vinyl alcohol) (EVOH) of the ethylene (Et) compositions of 33, 49, 75, and 89% (mol) using near-infrared spectroscopy. OH groups are mostly self-associated and only partly isolated in EVOH matrix, and the fraction of the isolated OH increases with the increase in Et composition. Interactions of water in EVOH were analyzed on the basis of the difference spectrum between the spectrum in a hydrated state and that in the dehydrated state of a sample. The water contained in an EVOH sample with a higher Et content shows a more distinct sharp combination band at about 5285 cm(-1) in addition to the main broad band at about 5150 cm-1. The former was assigned to the water that is one-to-one hydrogen-bonded to an isolated OH in the manner as OH::OH2 from the effect of the hydration on the near-infrared and infrared bands of the isolated OH. The latter was assigned to the water that is multiply hydrogen-bonded to surrounding associated OH groups and that does not cluster. (c) 2006 Wiley Periodicals, Inc.