Synthesis and self-assembly of a dual-responsive monocleavable ABCD star quaterpolymer

Abstract

ABCD star quaterpolymers acquired by precision synthesis may provide us with insights into self-assembly due to their fused architectures of different arm segments and a central core. Considering the crucial role of external stimuli in smart materials, the aims of this study are the facile synthesis of a pH/redox-responsive 4-arm miktoarm star and the study of its stimuli-dependent aggregation behaviors. A click reaction between azide/bromine-functionalized poly(ethylene glycol)-block-polystyrene (PEG-b-PSt) and alkyne/disulfide-functionalized poly(ε-caprolactone)-block-poly(tert-butyl acrylate) (PCL-b-PtBA) and subsequent selective hydrolysis were used to synthesize the target star with bromomethyl and disulfide functionalities in the core and a poly(acrylic acid) (PAA) segment. The PEG-PSt-PCL-PAA star can self-assemble into nanocapsules with hollow caves; the sizes and morphologies of these assemblies are dependent on pH and reductive stimuli due to stimuli-tunable destabilization and reassembly. By virtue of polyion and hydrogen bonding complexation using a partly quaternized copolymer, the nanocapsules can be further converted into versatile coaggregates such as compound vesicles and micelles, multicompartment vesicles, and hyperbranched micelles. Our research affords a robust method to synthesize core-functionalized stimuli-labile multicomponent miktoarm stars; these stimuli-responsive nanocapsules hold great promise in smart biomedical and interfacial materials.