The organocatalytic copolymerization of a derivative of trimethylene carbonate bearing protected 1,3-diols and D,L-lactide was studied. Homopolymerization of the cyclic carbonate from a PEG macroinitiator exhibited a controlled character, obeying pseudo first-order kinetics up to a conversion of similar to 60%. Longer reactions resulted in more polydisperse materials. Kinetics of copolymerization with DLLA showed a considerable accelerative effect of the ester on the polymerizability of the carbonate, attributed to relief of steric limitations that characterize the polymerization of this and other bulky cyclic carbonates. Postpolymerization hydrogenolysis, conveniently adjusted though catalyst concentration, yielded functional poly(ester carbonate)s (PECs) with enhanced chain mobility and hydrophilicity compared to protected analogues. PEG-b-PECs were further used as stabilizers for the formation of fluorophore nanoparticles via flash nanoprecipitation. Nanoparticle size and core properties were discussed in terms of hydrophobic block chemistry. The regulation offered by organocatalysts for the synthesis of diol-functionalized PECs with precise molecular characteristics provides access to biodegradable materials with readily tunable physicochemical properties through controlled installation of reactive handles. In the context of hydrophobic solute encapsulation, regulated functionalization allows fine-tuning of nanoparticle core properties, ultimately impacting solute loading, release, and stability.