Influence of Different Initiators Against the Mechanical Properties of Poly(e-caprolactone) used for Biodegradable Bone Implants

The ability of a strict control for the advanced macromolecular structures synthesis has been an important objective in our research. The development of polymers with defined structures and properties, aimed at biomedical applications, leads to complex and advanced architecture and diversity of the biodegradable polymers. Ring-opening polymerization is one of the most common methods for the synthesis of polymers with improved characteristics. Poly e-(caprolactone) (PCL) is prepared by ring-opening polymerization of the monomer e-caprolactone. The main factors which influence the ring-opening polymerization are the reaction conditions, such as the nature of the initiator, type and concentration of catalyst, reaction temperature and time. Stannous (II) 2-ethylhexanoate is used to catalyze the polymerization and alcohols are used as initiators. The initiators are also used to control the polymers molecular weight. Despite the long use of this catalyst in both industrial use and polymer research, several questions about the properties of the final product still remain. Our study describes the polymerization of e-caprolactone performed in the presence of catalyst (stannous (II) 2-ethylhexanoate) and initiator (1, 6 hexandiol or trimethylol propane) at moderate temperature (110�C). The polymerization of e-caprolactone was also performed in the presence of catalyst alone in order to evaluate the effect of the initiator against the polymers molecular weight. The obtained polymers were characterized by FTIR, GPC and TGA with respect to their mechanical properties. It is crucial to control the molecular weight of PCL for biomedical and pharmaceutical applications, because its molecular weight determines the hydrolysis rate. Several ratios among monomer, catalyst and initiator were studied, and we chose an optimum composition, in order to control the mechanical properties, degradation profiles respectively, and to avoid the cytotoxicity given by the reagents used.