SYNTHESIS AND CHARACTERIZATIONS OF. POLY(LACTIC ACID) AND ITS NANOPARTICLES

Abstract

Global demand, for environmentally sustainable products supplemented with increasing restrictions on the use of non-degradable polymers, has motivated researchers to explore for biodegradable and biocompatible polymers which can be produced from renewable resources. Polylactic acid (PLA) — a member of the biodegradable polyester family is an important biopolymer, which can address the above mentioned environmental threats. However, the high cost of production of PLA limits its application as a commodity plastic. Thus, a systematic investigation for the improvement of already established synthesis procedure for the cost effective production of PLA is still under evolution. Further, an innovative use of this biodegradable & biocompatible polymer has found its way in the drug delivery systems in the form of nanoparticles as evident from available published research work. Under the'. above backdrop, the present research has been planned to revolve around the above thoughts. Commercially, PLA is synthesized via ring opening polymerization (ROP) of lactide as well as through solution/melt polycondensation of lactic acid. The ROP is suffered from high production cost due to the involvement of complicated purification process of the lactide and azeotropic distillation of solvent. The second alternate route, which is solution polycondensation, is also not free from limitations as removal of solvent completely from the end product is difficult leading to poor quality of product. The third alternate route, i.e. melt polycondensation (MPC), produces low molecular weight PLA due to competitive .reaction of lactide formation and simultaneous degradation at high temperature.. Therefore, these methods of synthesis due to their. inherent weaknesses increase the production • cost substantially and thereby restricting their competitive use. Thus, many investigators have suggested an improved route which includes melt polycondensation under very high vacuum followed by solid-state polycondensation, which has potential, to offer high molecular weight PLA with high yield. (wt. %) comparable to the ROP process but at a lower cost. In the present experimental investigation, PLA is. synthesized by a two step process, of which the first step is melt polycondensation (MPC) under very high vacuum and the second step is solid-state polycondensation (SSP) which follows the first. After synthesizing PLA, its nanoparticles: (NPs) are also prepared and characterized.