Construction of a reactive diblock copolymer, polyphosphoester- block -poly(l -lactide), as a versatile framework for functional materials that are capable of full degradation and nanoscopic assembly formation

The development of a diblock copolymer, polyphosphoester-block-poly(l- lactide), which has potential for being fully degradable and biocompatible, was achieved by one-pot sequential ring-opening polymerizations (ROPs) of two cyclic monomers: alkyne-functionalized phospholane and l-lactide (LLA). A kinetic study of the polymerization in each step was investigated in a detailed manner by nuclear magnetic resonance (NMR) spectroscopy and gel permeation chromatography (GPC), revealing living/controlled characteristics with narrow molecular weight distributions and a linear increase of molecular weights vs monomer conversion and time. Subsequently, photoinduced thiol-yne "click" reactions with small-molecule thiols bearing either carboxylic acid or amino groups afforded amphiphilic diblock copolymers with carboxylate or amino side-chain functionalities along the polyphosphoester segment of the diblock copolymer backbone. Finally, direct dissolution of the two different types of amphiphilic diblock copolymers in aqueous solutions yielded well-defined spherical micelles with corresponding negative or positive surface charges, respectively, as confirmed by transmission electron microscopy (TEM), dynamic light scattering (DLS), and zeta potential analyses.