Preliminary studies of PLA synthesis by acid catalysis

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Abstract

Polylactic acid (PLA) is a synthetic polyester of great commercial value due to its renewable origin, biocompatible, biodegradable, bioresorbable, and mechanical properties. Consequently, there is a great interest in the development of alternative synthetic routes for obtaining PLA that allow for the substitution of the conventional tin octanoate-catalyzed method. Due to the cytotoxicity of this catalyst and its occlusion in the network after polymerization, more environmentally friendly synthetic alternatives are being sought. For this reason, a two-step synthesis route catalyzed successively with sulfuric acid and biocompatible metals was designed. In this work, the optimization of the first step was performed, which consists in a Fischer esterification of lactic acid using acid as catalyst. To determine the best conditions, a catalyst concentration was carried out in the range of 0 to 3% v/v. According to the obtained results, optimal catalyst concentration conditions were found that generate the highest amount of condensation product while simultaneously achieving the shortest reaction time and the highest viscosity. Furthermore, the composition of the synthesis products was verified using ¹H-NMR and FT-IR, identifying specific signals of PLA oligomer molecules among the products.