One-Pot Synthesis of Polysarcosine Molecular Bottlebrushes: From Monomer to Worm-Like Nanostructures

Polysarcosine (PSar) has been recognized as a promising alternative to poly(ethylene glycol) (PEG) in biomedical fields. The development of efficient methods for synthesizing PSar with complex architectures is therefore essential for creating optimal biomaterials. Herein, we propose a "one-pot" approach for synthesizing PSar molecular bottlebrush (MBB) with abundant active terminal amino groups through the combination of N-carboxyanhydride (NCA) polymerization and monomer-emulsified aqueous ring-opening metathesis polymerization (ME-ROMP). Briefly, the NCA polymerization of Sar-NCA monomer using norbornenyl amino (NB-NH₂) as the initiator was first conducted to prepare norbornenyl terminal PSar (NB-PSar). Subsequently, without purification, this NB-PSar macromonomer was employed to synthesize PSar MBBs with precise architecture by ME-ROMP in the CH₂Cl₂/H₂O (v/v = 1/10) mixtures through a grafting-through strategy. Kinetic studies indicated that the entire process could be completed within 20 min with near-quantitative conversion, and worm-like PSar MBBs with varied length and diameter could be easily synthesized by varying the feed ratios. Moreover, the terminal secondary amines of PSar side chains were retained, which could be further utilized for the surface modification of the MBBs. This work provides a one-pot approach for worm-like nanostructured PSar materials, which are expected to hold promising potential for creating advanced biomaterials.