Biopolyester from ricinoleic acid: Synthesis, characterization and its use as biopolymeric matrix for magnetic nanocomposites

This work presents a study on the production of ricinoleic acid-based biopolyester derived from castor (Ricinus communis) oil with and without in situ insertion of magnetic Fe3O4 nanoparticles with their surface modified by ricinoleic acid. Self-catalyzed reactions, due to H+ from ricinoleic acid, which behaves as a Bronsted-Lowry acid, were performed in a batch bulk polymerization process and some kinetic studies were carried out. It was also observed that the magnetic Fe3O4 nanoparticles act as Lewis acid catalysts during the polymerization. The ester formations were followed by acid value and FTIR spectra and it was observed that the reactions without magnetic nanoparticles (only Bronsted self-catalyzed reaction) reached a steady-state after 14 h of reaction. For the reactions with surface-modified magnetic Fe3O4 nanoparticles the steady-state rate was reached in 6 h of reaction. In the absence of the magnetic nanoparticles, it was observed at 190 degrees C that the consumption of the ricinoleic acid follows a second-order behavior and increasing 20 degrees C the reaction rate was 15% faster. The polymeric materials have been characterized in order to provide information on their structural and thermal features. It was verified that the thermal stability of the product is significantly increased with the reaction conversion. Magnetic measurements were and have shown that the material exhibited a superparamagnetic behavior when using magnetic Fe3O4 nanoparticles. (C) 2014 Elsevier B.V. All rights reserved.