Synthesis of PLGA using a Csub(3)-synmmetric Zr (IV) amine tris(phenolate) alkoxide initiator and the effects of gamma radiation on its properties

Abstract

In this paper, we report the preparation and characterisation of poly(lactic-co-glycolic) acid (PLGA) using a C3-symmetric Zr (IV) amine tris(phenolate) alkoxide initiator. Although the zirconium alkoxide initiator is slower than the most commonly used Sn(Oct)2, relatively high molecular weights were obtained at a temperature of 130 C, for a monomer to initiator ratio of 1000/1 (24 h) and 5000/1 (48 h). The degree of racemisation also depends on the initiator used. The reactions performed with the zirconium initiator showed a higher degree of racemisation when compared to those performed with Sn(Oct)2. A slight increase in the racemisation with time was also observed. The effects of gamma radiation on PLGA were also studied. Doses commonly applied to sterilise materials for biomedical applications were employed—10, 18, 25 and 50 kGy. The molecular weight of all samples irradiated decreased in a dose-dependent fashion—up to 56 % loss for 10 kGy and 72 % for 50 kGy—but were less pronounced for higher doses. Changes in thermal properties, such as melting point, glass transition temperature and enthalpy of crystallisation and fusion, were also observed after irradiation.