AbstractThe equilibrium water content (EWC) of thermoplastic 2‐hydroxypropyl methacrylate and 2‐hydroxyethyl methacrylate homopolymers from technical grade monomer and of copolymers of the latter with methyl methacrylate has been measured in distilled water and in phosphate‐buffered saline (PBS). In distilled water, as expected, EWCs increased monotonically with the proportion of hydrophilic monomer in the polymer and showed only a small dependence on molecular weight. In contrast, the degree of swelling (and in some cases dissolution) and “freezable” water content of polymers in PBS were shown to be anomalously high and to be a consequence of ionization at pH 7.4 of methacrylic acid incorporated into the polymer in small quantity (<1 mol ) as an impurity. Initial studies indicated a strong relationship between copolymer molecular weight and small molecule permeability in distil
展开▼
