title: Surface modification of tricalcium phosphate for improvement of the interfacial compatibility with biodegradable polymers.
abstract: The surface of tricalcium phosphate (TCP) filler particles was activated by treatment with dilute aqueous phosphoric acid. ATR-IR spectra indicated the formation of calcium hydrogen phosphate dihydrate at the surface. Oligo(lactone)s were formed by the subsequent reaction of the activated TCP with L-lactide and epsilon -caprolactone, respectively, at 150 degrees C without any additional catalysts. After extraction of the oligo(lactide), the residue of modified TCP-included calcium lactate whereas the water of crystallization of the dihydrate disappeared as shown by ATR-IR spectroscopy. Owing to the insolubility of TCP in common solvents, the analogous reaction between water-soluble disodium hydrogen phosphate dihydrate and L-lactide was used to study the kind of chemical bonds by high-resolution NMR spectroscopy. The 1H and 13C NMR spectra of the reaction product also pointed out the presence of calcium lactate. Additionally, signals were found indicating a covalent attachment of lactic acid units onto the phosphorus. For the preparation of composites, poly(L,DL-lactide) was mixed with TCP and modified TCP, respectively, in a ratio of 75/25 (w/w) and directly injection moulded into tensile test specimens at a barrel temperature of 180 degrees C. Although mechanical properties were not improved, scanning electron microscopy (SEM) indicated a better interfacial phase interaction in the composite with the modified TCP. Chemical bonds between filler and polymer matrix are assumed to be formed by transesterification reactions.
authors.affiliation: Institute of Materials Sciences, Polymer Engineering, Martin-Luther University Halle-Wittenberg, D-06099 Halle/Saale, Germany.
authors.forename: Carmen
authors.initials: C
authors.lastname: Kunze
authors.forename: Thomas
authors.initials: T
authors.lastname: Freier
authors.forename: Ekaterina
authors.initials: E
authors.lastname: Helwig
authors.forename: Barbara
authors.initials: B
authors.lastname: Sandner
authors.forename: Dieter
authors.initials: D
authors.lastname: Reif
authors.forename: André
authors.initials: A
authors.lastname: Wutzler
authors.forename: Hans Joachim
authors.initials: HJ
authors.lastname: Radusch
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry*; D001673:Biodegradation, Environmental; D017610:Calcium Compounds / Q000032:analysis; D002130:Calcium Phosphates / Q000737:chemistry*; D003460:Crystallization; D007773:Lactates / Q000032:analysis; D009682:Magnetic Resonance Spectroscopy; D008855:Microscopy, Electron, Scanning; D010756:Phosphoric Acids; D013055:Spectrophotometry, Infrared; D013499:Surface Properties; D013718:Tensile Strength; D013816:Thermodynamics
chemical_list: D001672:Biocompatible Materials; D017610:Calcium Compounds; D002130:Calcium Phosphates; D007773:Lactates; D010756:Phosphoric Acids; C485817:beta-tricalcium phosphate; C110051:calcium lactate; C030242:phosphoric acid; C018392:tricalcium phosphate