The conformational stability of tactic poly(2‐hydroxyethyl methacrylate) in aqueous salt solutions

Abstract

AbstractThe conformational stability of tactic poly(2‐hydroxyethyl methacrylate) (PHEMA) in aqueous salt solutions was investigated by measurements of swelling, surface‐free energy, and differential scanning calorimetry, as this polymer in water is sensitive in various electrolytes. In the case of inorganic salts, the major role for the salt effect is played by the anions, and the exposure of hydrophobic components at the PHEMA surface can be correlated with the increase of the degree of swelling. The influence of cations is considerably weaker. In the case of organic salts, tetraalkylammonium halides cause the chain extension more effectively with the increase of alkyl chain length in the cations. This result indicates that the breakdown of the hydrophobic parts in PHEMA provides an important clue on conformational stability. The amount of water molecules bound with the hydrophilic sites of tactic‐PHEMA mainly depends on the chain extension and the hydration of cations. Since the sites in tactic‐PHEMA influenced by the cation and the anion are different, their effects cause the conformational transition at a specific range of salt concentration. © 1993 John Wiley & Sons, Inc.