Synthesis of antithrombotic poly(carbonate-urethane)s through a sequential process of ring-opening polymerization and polyaddition facilitated by organocatalysts

We have first confirmed that an organic acid, diphenyl phosphate (DPP) is effective in a sequential process of ring-opening polymerization (ROP) of a cyclic carbonate and polyaddition with a diisocyanate. More potent triflic acid (TfOH) exhibited higher catalytic activities for both ROP and polyaddition than DPP and pairs of thiourea and basic catalysts such as cyclic amidines and sparteine. However, DPP-catalyzed ROP was more manageable than that using TfOH regarding control over the molar-mass dispersity of the resultant polycarbonates that matters to the final polyurethanes. As a consequence of DPP-catalyzed one-pot synthesis of poly(carbonate-urethane)s, we have obtained segmented polyurethanes comprising a poly(trimethylene carbonate) analog with ether side chains as a soft segment and hexamethylene diisocyanate as a hard segment. Although the whole reaction took a few days, high molecular weight over 50 k was achieved for the resultant polyurethanes whose texture suggested improved physical properties. Nevertheless, the polyuretahnes maintained low platelet adhesion properties. This antithrombotic polyurethane became more promising as a candidate base material for resorbable artificial blood vessels. Furthermore, this sequential synthesis by single organocatalysts enables the efficient production of functionalized poly(carbonate-urethane)s.