Synthesis of PLGA using a C₃-symmetric Zr (IV) amine tris(phenolate) alkoxide initiator and the effects of gamma radiation on its properties

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 upon 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 are 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.