Sorption of water was studied in polymer complexes formed by poly(methacrylic acid) with polyethylene glycol), poly(vinyl pyrrolidinone), poly(dimethylaminoethyl methacrylate) and a quaternary ammonium base. Water sorbed by the component homopolymers was also determined (Table 2) and the data were compared with those on water sorbed by the polymer complexes (Table 3). Differential scanning calorimetry was used to establish the amount of nonfreezable bound water and compared with the water sorption data determined for both homopolymers and polymer complexes (Fig. 2). At high relative humidities, the amounts of bound water and absorbed water were similar (Table 1). The experimentally observed amounts of water absorbed by the homopolymers at equilibrium were found to differ considerably from those calculated on the basis of reported data  (Table 2). The additivity rule allows to calculate the uptake of water (Table 3) by the complexes from the data established for the homopolymers; the data are usually close to the experimental amounts of water absorbed by the polymer complex; however, differences between the calculated and observed data can be significant presumably on account of the specific structure or, occasionally, a semicolloidal form of the complex (Table 3).
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