A Solvent-Free Route to Non-Isocyanate Poly(carbonate Urethane) with High Molecular Weight and Competitive Mechanical Properties

A series of non-isocyanate linear poly(carbonate urethanes) (PCUs) were prepared through an environmentally friendly route based on dimethyl carbonate, 1,6-hexanediol and 1,6-hexanediamine. Bis-1,6-hexamethylencarbamate (BHC) was first synthesized from diamine and excess dimethyl carbonate. To prevent the detrimental crosslinking problem, a new "hard segment first" route was developed. In this route, the polyurethane diol was first prepared by the reaction between BHC and 1,6-hexanediol. Polycarbonate diol was obtained by the reaction of dimethyl carbonate and 1,6-hexanediol. The subsequent polycondensation of polyurethane diol and polycarbonate diol led to linear PCUs. The polymers were characterized by GPC, FT-IR, H-1 NMR, C-13 NMR, DSC, WAXD, TGA and tensile testing. The results indicated that the PCUs possessed a linear structure and high molecular weight with a number-average molecular weight of up to 60,000 g/mol. It should be noted that the PCUs exhibited good thermal properties with a composition-dependent melting point ranging from 60 degrees C to 137 degrees C, and a good mechanical strength, with tensile strength values lying between 17 MPa and 29 MPa and elongation at break varying from 665% to 26%. Considering the green procedure and raw materials as well as the good processability and mechanical properties of the resultant PCUs, this kind of aliphatic thermoplastic PCU offers great potential to be industrialized and applied in the biomedical field such as tissue scaffolds and cardiovascular implants.