Amphiphilic Polyoxazoline-block-Polypeptoid Copolymers by Sequential One-Pot Ring-Opening Polymerizations

Amphiphilic block copolymers possess great potential as biomaterials in drug delivery and gene therapy. Herein, pseudopeptidic-type diblock copolymer of poly(2-oxazoline)-block-polypeptoid (POx-b-POI) is presented and synthesized. Poly[2-(3-butenyl)-2-oxazoline]-block-poly(sarcosine) (PBuOx-b-PSar) comprising hydrophobic POx segment bearing alkenyl side chain and hydrophilic POI segment of N-methyl glycine, viz., sarcosine, is prepared by ring-opening polymerization (ROP) through a one-pot and three-step route. Diphenyl phosphate initiates ROP of BuOx, and then the living chain end of PBuOx is quenched by ammonia to obtain PBuOx-ammonium phosphate in situ, the active ammonium group initiates ROP of sarcosine N-carboxy anhydride. PBuOx-b-PSar with controlled molecular weights (4.7–10.8 kg mol⁻¹) and narrow dispersities (Ð_M 1.15–1.21) are characterized by ¹H NMR, ¹³C NMR, and size-exclusion chromatography. Dynamic light scattering and transmission electron microscopy analysis reveal that PBuOx-b-PSar self-assembles into nanostructures of average diameter D_H of 37–109 nm in aqueous solution. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide test demonstrates the cytocompatibility (relative cell viability > 80%) of the PBuOx-b-PSar. In view of the self-assembly and biocompatibility, the readily prepared diblock copolymers may hopefully be used in biomedical applications. (Figure presented.).