Y-shaped poly(ethylene glycol) and poly(trimethylene carbonate) amphiphilic copolymer: Synthesis and for drug delivery Part A Polymer chemistry

New Y-shaped (AB₂-type) amphiphilic copolymers of poly(ethylene glycol) (PEG) with poly(trimethylene carbonate) (PTMC), PEG-b-(PTMC)₂, were successfully synthesized by the ring-opening polymerization (ROP) of TMC with bishydroxy-modified monomethoxy-PEG (mPEG). First, a bishydroxy functional ROP initiator was synthesized by esterification of acryloyl bromide with mPEG, followed by Michael addition using excess diethanolamine. A series of Y-shaped amphiphilic PEG-(PTMC)₂ block copolymers were obtained via ROP of TMC using this PEG with bishydroxyl end groups as macroinitiator and ZnEt₂ as catalyst. The amphiphilic block copolymers with different compositions were characterized by gel permeation chromatography (GPC) and ¹H NMR, and their molecular weight was measured by GPC. The results showed that the molecular weight of Y-shaped copolymers increased with the increase of the molar ratio of TMC to mPEG-(OH)₂ initiator in feed while the PEG chain length was kept constant. The Y-shaped copolymer mPEG-(PTMC)₂ could self-assemble into micelles in aqueous medium and the critical micelle concentration values of the micelles decrease with increase in hydrophobic PTMC block length of mPEG-(PTMC)₂. The in vitro cytotoxicity and controlled drug release properties of the Y-shaped amphiphilic block copolymers were also investigated.