Preparation of pyridine end functionalized copolymers from eutectic mixtures of L-lactide and trimethylene carbonate

Poly (L-lactide) (PLLA) is a polymer that has several applications in the biomedical area, being used including in controlled-release systems. However, this polymer has certain limitations. One of them is the fact that its degradation products are acidic compromising tissues. Therefore, several studies have been carried out with the objective of incorporating comonomers in its structure. In this context, the trimethylene carbonate (TMC) comonomer has proved to be an excellent choice to overcome the limitations of PLLA, as the degradation products of TMC are not acidic and are well tolerated by the human body. In this work, random copolymers functionalized with a pyridinic binder were prepared, with the monomers L-lactide and trimethylene 1,3-carbonate, via reactions from their eutétic melts. These reactions were carried out under different reaction conditions and with the 1,8-diazabicyclo[5.4.0]undec-7-eno (DBU) organocatalyst. The hydrogen and carbon nuclear magnetic resonance analyses (NMR 1H and 13C) confirmed the structure and functionalization of the copolymers. In addition, it was possible to observe from the composition data, greater incorporation of LLA when the reactions were carried out at room temperature. Gel permeation chromatography (GPC) analysis revealed that the majority of the samples exhibited a monomodal molar mass distribution, with number-average molar masses (Mn) ranging from 4665 to 27 950 g/mol and narrow polydispersity indices (PDI) in most cases. The results of differential scanning calorimetry show a gradual increase in the Tg of the copolymer as the L-lactide content increases.