Adsorption of a polyfunctional surface-active amine accelerator on hydroxyapatite

Abstract

Adsorption of a polyfunctional surface-active amine polymerization accelerator (“PolySAM-1”) from chloroform solutions on synthetic hydroxyapatite is exhaustive and completely irreversible from very dilute solutions. The adsorption is irreversible until the formation of a “monomolecular layer,” at which point the additional adsorption is reversible. At relatively low equilibrium concentrations the adsorption is not exhaustive and the isotherm is linear. Adsorption isotherms of the adsorbate which is reversibly bound and of the adsorbate on a hydroxyapatite sample containing a preadsorbed monolayer of the same are identical and follow the Langmuir plot. Evidence shows that the irreversibly adsorbed material is probably chemisorbed. The tensile strength of a polymer, filled with synthetic hydroxyapatite having an adsorbed monolayer of PolySAM-1, did not exceed that of the polymer filled with untreated apatite for any of the polymerization-initiating systems that were studied. This implies that tertiary aromatic amine accelerators of this type do not form free radical sites capable of initiating or terminating significant graft polymerization under these conditions after their reaction with benzoyl peroxide.