To study the relationship among relaxation peaks observed in dynamic mechanical experiments and the structure of poly(ethylene-co-vinyl acetate) (EVA), EVA copolymers with different substitution in the carbonyl group were synthesized. EVA was hydrolyzed to obtain poly (ethylene-co-vinyl alcohol) and was subsequently reacted with formic, hexanoic, and octanoic acids. The copolymers synthesized were characterized by infrared spectroscopy. Analysis of the DMA spectra of the copolymers showed that their relaxation behavior depends on the vinyl acetate concentration. The alpha- and beta-transitions were observed in EVA copolymers with 8 and 18 wt % of functional groups, and the relationship among relaxation process with the structure of polymer was investigated. (c) 2005 Wiley Periodicals, Inc.