Calcitropic Non-ionic Surfactant Lamellar Phases

摘要

The aqueous non-ionic surfactant decaethylene glycol hexadecyl ether (C_(16)EO_(10)), in the presence of CaCl_2, forms novel "calcitropic" lamellar liquid-crystal phases. Thin films of these materials display notable structure sensitivity to the hydrophobicity or hydrophilicity of the underlying support. A structure-bonding model of these materials is based upon Ca~(2+)-crown ether-like coordination to the decaethylene glycol head group of one or two of the surfactant molecules. Ca~(2+) binding of two surfactant head groups, makes possible cis- and trans-conformations for the alkyl tails, resulting in normal and inverted structures with preferences for hydrophilic and hydrophobic surfaces, respectively. The extent of Ca~(2+) ion clustering in the head group determines the geometrical packing requirements of the surfactant and the overall dimensions of the resulting lamellar liquid-crystal phases. The effect of various phosphate reagents (H_3PO_4, KH_2PO_4, K_3PO_4) on these "calcitropic" liquid-crystal phases has also been investigated. The conditions that favor the deposition of different calcium phosphate solid phases from these "calcitropic" lamellar precursors have been investigated, with a view to their possible use as "controlled release biomaterials" for supplying thin-film and nanocrystalline forms of calcium phosphate for bone restoration, replacement, and augmentation applications. The nontoxic, biocompatible, biodegradable, and inexpensive nature of oligoethylene glycol alkyl ethers is a distinctive advantage for these kinds of endeavors.