Amphiphilic diblock copolymers bearing pendant aromatic acetal groups: Synthesis and tunable pH-triggered assembly/disassembly transition behavior

A novel aromatic acetal-based acid-labile monomer 2-phenyl-5-ethyl-5-acryloxymethyl-1,3-dioxacyclohexane (HEDPA) was synthesized and polymerized by reversible addition fragmentation chain transfer (RAFT) polymerization using alkynyl functional chain transfer agent (CTA-Alk). Afterward, a series of amphiphilic diblock copolymers composed of fixed hydrophobic poly(2-phenyl-5-ethyl-5-acryloxymethyl-1,3-dioxacyclohexane) (PDAEP) segments and various lengths of hydrophilic mPEG segments were prepared through click reaction between alkynyl-terminated PDAEP and azido-terminated mPEG. The self-assembly behaviors of the diblock copolymers were investigated by dynamic light scattering (DLS), transmission electron microscopy (TEM), fluorescence spectroscopy, and ¹H NMR. These results indicated that the diblock copolymers could self-assemble into nano-sized micelles with PDAEP cores and PEG coronas in aqueous solution. DLS, fluorescence spectroscopy and UV-vis spectroscopy were used to monitor the pH-triggered assembly/disassembly transition of the micelles. These results showed that the assembly/disassembly transition behaviors of the diblock copolymers micelles can be adjusted by changing the lengths of the mPEG segments.