Synthesis of poly(limonene) via O-ATRP: a proposal to increase molar mass and absence of metal residues in the production of a renewable source polymer

Abstract

Limonene is a cyclic monoterpene that has the potential to be used as monomer in poymerizations. This compound can be commercially synthesized or obtained by extracting from industrial waste (citrus peel), allowing its use in large scale applications. In addition to the prospect of generating a material from a renewable and non-toxic source, this project aims to create a material with characteristics that allow its application in several areas, such as coatings, adhesives, packaging or more noble applications - clinical implants and electronic components. However, poly(limonene) synthesis of via free radical polymerization is currently impracticable, since chain transfer reactions have competitive rates with propagation. This results in low conversion (~ 10%) and molecular weight (~ 1000 g mol-1). The use of this material as homopolymer or incorporated into other materials is not technically-financially attractive, which has discouraged its production on an industrial scale. Several researches have used different polymerization techniques of limonene aiming the increase of its conversion and molecular weight. However, none showed significant results of increase of these process variables. There is a need for new efforts to enable the production of this environmentally friendly material. Organocatalized Atom-Transfer Radical Polymerizatiom (O-ATRP) is a powerful controlled synthesis technique of polymeric materials, its main advantage being the absence of metallic residues in the resulting polymers, making it possible to apply in medical and electronic fields. According to the theory of the persistent radical effect, which underlies macromolecular control in controlled polymerizations, in these processes chain transfer reactions and terminations are reduced, allowing obtaining of polymers with low dispersities. Based on this hypothesis, this proposal has as main objective to develop a mathematical modeling to evaluate the effect of each reaction step in the synthesis of poly(D-limonene) via O-ATRP on its properties (molecular weight, dispersity and monomer conversion) and confirm whether, in fact, it is possible to suppress such reactions and generate a polymer with high molecular weight and monomer conversions. (AU)