Random Copolymerization of epsilon-Caprolactone and L-Lactide by Ring Opening Polymerization Using a Co/N-Doped Carbon Framework as Catalyst

The synthesis and use of MOF-derived Co/NCF (N-doped carbon framework) material as a heterogeneous catalyst for copolymers synthesis via ring-opening polymerization (ROP) are reported for the first time. The Co/NCF material is applied for the copolymerization of L-lactides (LA) and epsilon-caprolactone (epsilon-CL) as monomers via ROP in bulk without any solvent or co-catalyst. The as-prepared catalyst is characterized using XRD, TPD, XPS, SEM, and TEM analytical techniques. At the same time, H-1 and C-13-NMR spectroscopy were used to analyze the microstructure of the copolymer confirming the random copolymer structure. The average r values calculated from the heterodiad analysis of the H-1 NMR, data were r(LA) = 0.96 and r(CL) = 0.93 and L value calculated from the triads analysis of C-13 NMR, data were L-LA = 3.17 and L-CL = 2.79, respectively. It has been observed that the melting temperature and glass transition temperature of the copolymer increases with higher LA content. The XRD and DSC analyses also confirmed that the as-synthesized copolymer possesses two phases corresponding to the polylactide and polycaprolactone, respectively. Additionally, the activity of Co/NCF is also compared with other Co-based heterogeneous catalysts to demonstrate its ability.