Calcium phosphate mineralization beneath monolayers of poly(n-butylacrylate)-block-poly(acrylic acid) block copolymers

Amphiphilic poly(acrylic acid)-block-poly(n-butylacrylate) block copolymer films at the air-water interface have been mineralized with calcium phosphate. The polymers form stable monolayers at the free surface. Their stability is virtually independent of ion strength or pH changes in the subphase. The outcome of calcium phosphate crystn. depends on the calcium and phosphate concns., the stirring rate of the subphase, and the subphase pH. At low calcium and phosphate concns. (2 mM), uniform polymer-calcium phosphate hybrid films form. Higher calcium and phosphate concns. yield less ordered films, which often contain large blocks of material beneath the polymer monolayer. Occasionally, also filaments similar to samples described by Peytcheva et al. (Colloid Polym. Sci., 2002, 280, 218) are obsd. Films mineralized at pH values below ca. 6 contain particles that are a few nanometers apart and the resulting films retain some flexibility. Films grown above pH 6 have a higher degree of mineralization. They are stiff and tend to break upon mech. stress. Overall, the paper illustrates that low calcium phosphate supersatn. in the subphase and a well-defined (but not cryst.) interface are crucial for controlling calcium phosphate mineralization. As a result, the current study could serve as a model for biol. mineralization which is more closely related to Nature than films made from e.g. detergents or low mol. mass compds. [on SciFinder (R)]