Preparation of biomimetic composites of hydroxyapatite and star-shaped poly(2,2-dimethyl trimethylene carbonate)s terminated with carboxyl end-groups

Abstract

Biomimetic composites based on star-shaped poly(2,2-dimethyl trimethylene carbonate)s fitted with carboxyl end-groups (PDTC(COOH)4) and hydroxyapatite (HA) were prepared using grinding technique under solvent free conditions. The required carboxyl groups were introduced at the polymer by reaction of hydroxyl groups with succinic anhydride. The synthesis of star-shaped, hydroxyl terminated precursors was achieved applying ring-opening polymerization of 2,2-dimethyl trimethylene carbonate (DTC) conducted in the presence of multi-hydroxyl alcohol as an initiator and tin octoate (Sn(Oct)2) as a catalyst. The thermal properties of obtained polymers were studied by DSC and TGA. Composites containing 15 wt% of HA were characterized regarding the HA distribution in the polymer matrix, crystallinity and thermal stability. Mechanical studies have demonstrated that PDTC(COOH)4/HA composites exhibit very good mechanical properties characterized by the elastic modulus (264 MPa and 365 MPa) in the range of the elastic modulus of cancellous bone.