Interaction of water in polymers: Poly(ethylene‐ co ‐vinyl acetate) and poly(vinyl acetate)

We studied the interaction of water in poly(ethylene‐ co ‐vinyl acetate) of various vinyl acetate compositions and poly(vinyl acetate), on the basis of the infrared spectrum of the water dissolved therein. The spectrum shows a very sharp and distinct band at about 3690 cm −1 (named as A), and less‐sharp two bands around 3640 (B) and 3550 cm −1 (C), the A band being outstanding especially at a low vinyl acetate composition. As the vinyl acetate composition increases, the A band decreases in intensity relative to the C band, whereas the B band increases contrarily. Analysis of the spectral change has elucidated that one‐bonded water (of which one OH is hydrogen‐bonded to the CO of an ester group and the other OH is free) and two‐bonded water (each OH of which is hydrogen‐bonded to one CO) coexist in the copolymer and that two‐bonded water increases in relative population with increasing vinyl acetate composition. Dissolved water is entirely two‐bonded in poly(vinyl acetate), in which CO groups are densely distributed in the matrix. We proved that dissolved water in polymers is hydrogen‐bonded through one or two OH groups to the possessed functional groups but does not cluster.