The proposal focuses on the fundamental aspects of synthesizing polymer/ceramic composites with a well-characterized interface. Three routes are proposed representing a controlled increase in the expected level of interaction between the polymer and the ceramic: 1. Physical or chemical adsorption, 2. In situ precipitation of hydroxyapatite (HA), within the polymer backbone and, 3. Chemically bonding HA with the polymer network. In case 1, the HA will be mechanically mixed in a solution of the dissolved polymer followed by evaporation of the solvent. The polymers selected for this study will be polycaprolactone (PCL), and poly (lactic-co-gylcolic acid) (PLGA), as well blends of these polymers. Additionally, commercial HA as well as synthesized HA will be incorporated to study the effect of the morphology of HA on mechanical strength. In case 2, HA will be chemically synthesized in the presence of the polymer in a solvent medium suitable for solvation of the polymer. This particular synthetic protocol will provide a better molecular mixing of HA in comparison to case 1 and lead to chemisorbed species. Polycaprolactone will be examined as preliminary results with PCL and HA indicate an in situ formaiton is viable. In case 3, novel dendrimers will be synthesized and a chemical reaction will be initiated between the calcium and phosphorous between the polymer and HA. Dendrimers with terminal amino groups such as poly(L-lysine) can be derivatized by amide formation with glycolates giving terminal alcohols. These terminal functional groups attached to the dendrimer can serve as bridging sites for attachment of reactive calcium and phosphate alkoxy groups that can polymerize to form HA. This process will provide a unique way to covalently bond HA to a polymer. The above three methods provide a novel way of synthesizing polymer/ceramic composites with controlled interfacial polymer/ceramic interface using spectorscopy, x-ray, high-resolution electron microscopy, thermal analyses and mechanical testing.
The results from the present studies should have an impact on the synthesis, control of interface structure, and design of polymer/ceramic composites. If successful, this project will enhance the understanding of the in situ synthesis within a polymeric Or dendrimeric network. Thus the synthetic processes developed here will form the basis of generating new composite materials that could be used for a number of engineering applications, including tissue engineering.
