Synthesis and Microstructural Characterization of Ethylene Carbonate−ε-Caprolactone/l-Lactide Copolymers Using One- and Two-Dimensional NMR Spectroscopy

Copolymers containing ethylene carbonate (EC) and ε-caprolactone (CL)/ l -lactide (LA) units of different compositions were synthesized by the ring-opening polymerization method using the SmI 2 /Sm initiator system. EC was non-homopolymerizable using the same initiator. A maximum of 19 mol % EC was incorporated into the polycaprolactone backbone. The microstructure of these copolymers was analyzed by one- and two-dimensional NMR spectroscopies. The triad sequence distribution centered at CL has been obtained from 13 C NMR spectroscopy. 2D 1 H− 13 C HMQC (heteronuclear multiple-quantum correlation) and HMBC (heteronuclear multiple-bond correlation) spectra were used to confirm the existence of EC as isolated units and CL/LA in the blocks. The complete and correct assignment of peaks in the 13 C NMR spectrum of previously reported EC−CL copolymers is also done on the basis of 1 H− 13 C HMQC and HMBC spectroscopic techniques.