NMR study of adsorbed water on acrylic acid‐grafted and methacrylic acid‐grafted cellulose

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Abstract
The water‐adsorbing properties of cellulose samples which had been graft copolymerized with hydrophilic vinyl monomers using ceric salt as an initiator were investigated by means of the width of the high‐resolution NMR absorption spectrum, water retention, and moisture regain of the samples. In the change of the width at half‐value of the spectrum with per cent grafting, a maximum value followed by a minimum value was observed on samples both grafted with acrylic acid and methacrylic acid. Thus, the effect of grafting on the water‐adsorbing properties appeared not to be simple. Though no special change in the water retention by grafting was observed, the per cent grafting dependence on the moisture regain in high relative humidity showed a peculiar and definite relation. The per cent grafting giving maximum moisture regain was about 8% and 18% for acrylic acid and methacrylic acid, respectively, and this agreed very well with the minimum widths at half‐value. The change in the glass transition temperature of the sample—water system caused by grafting is also described.