Two-Dimensional Supramolecular Assemblies from pH-Responsive Poly(ethyl glycol)-b-poly(l-glutamic acid)-b-poly(N-octylglycine) Triblock Copolymer

Amphiphilic block copolymers containing polypeptides can self-assemble into a variety of nonspherical structures arising from strong interactions between peptide units. Here, we report the synthesis of a pH-responsive poly(ethyl glycol)-block-poly(l-glutamic acid)-block-poly(N-octylglycine) (PEG-b-PGA-b-PNOG) triblock copolymers by sequential ring-opening polymerization using amine-terminated poly(ethyl glycol) as the macroinitiator followed by selective deprotection of the benzyl protecting group. The obtained triblock copolymer can be directly dispersed in aqueous solution with hydrophilic PEG, pH-responsive PGA block, and hydrophobic PNOG. We present a systematic study of the influence of pH, molar fraction, and molecular weight on the self-assemblies. It was found that the PEG-b-PGA-b-PNOG triblock tends to form two-dimensional nanodisks and nanosheet-like assemblies. The nanodisk-to-nanosheet transition is highly dependent on the pH and molar fraction despite the different molecular weights. We demon...