Controlled Syntheses of Well-Defined Poly(thionophosphoester)s That Undergo Peroxide-Triggered Degradation

We reported the preparation of well-defined poly­(thionophosphoester)­s as oxidation-responsive materials that undergo peroxide-triggered degradation. The polymers were synthesized via the controlled ring-opening polymerization of cyclic thionophosphoesters initiated with hydroxyl terminal small molecule and macromolecular initiators and catalyzed with 1,5,7-triazabicyclo[4.4.0]­dec-5-ene in tetrahydrofuran at room temperature. The resulting poly­(thionophosphoester)­s were characterized in detail by NMR spectroscopy and size exclusion chromatography. Polymerization of cyclic oxophosphoester (PO) monomers exhibited broad molecular weight distribution and severe side reactions, while narrow molecular weight distribution (Đ M ∼ 1.1) was achieved without significant transesterifications using thionophosphoester (PS) monomers. The reaction kinetics of thionophosphoester monomers were in agreement with living polymerization characteristics. Furthermore, by replacing PO bond by PS, the polymers changed from hydrophilic to hydrophobic. These well-controlled sulfur-containing polymers are more resistant to hydrolytic degradation but undergo peroxide-triggered degradation. Poly­(thionophosphoester)­s are thus promising in the field of biomedical materials.