CALCITROPIC NONIONIC SURFACTANT LAMELLAR PHASES

The aqueous non-ionic surfactant decaethylene glycol hexadecyl ether ( C(16)EO(10)), in the presence of CaCl2, forms novel ''calcitropic'' la mellar liquid-crystal phases. Thin films of these materials display no table structure sensitivity to the hydrophobicity or hydrophilicity of the underlying support. A structure-bonding model of these materials is based upon Ca2+-crown ether-like coordination to the decaethylene g lycol head group of one or two of the surfactant molecules. Ca2+ bindi ng of two surfactant head groups, makes possible cis- and trans-confor mations for the alkyl tails, resulting in normal and inverted structur es with preferences for hydrophilic and hydrophobic surfaces, respecti vely. The extent of Ca2+ ion clustering in the head group determines t he geometrical packing requirements of the surfactant and the overall dimensions of the resulting lamellar liquid-crystal phases. The effect of various phosphate reagents (H3PO4, KH2PO4, K3PO4) On these ''calci tropic'' liquid-crystal phases has also been investigated. The conditi ons that favor the deposition of different calcium phosphate solid pha ses from these ''calcitropic'' lamellar precursors have been investiga ted, with a view to their possible use as ''controlled release biomate rials'' for supplying thin-film and nanocrystalline forms of calcium p hosphate for bone restoration, replacement, and augmentation applicati ons. The nontoxic, biocompatible, biodegradable, and inexpensive natur e of oligoethylene glycol alkyl ethers is a distinctive advantage for these kinds of endeavors.